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RFM22B/23B ISM TRANSCEIVER MODULE Fe atures Applic ations Desc ription HopeRF's RFM22B/23B are highly integrated, low cost,433/868/915MHZ wireless ISM transceivers module. The low receive sensitivity coupled with industry leading +20dBm output power ensures range and improved link performance. Built- in antenna diversity and support for frequency hopping can be us ed to further extend range and enhance performance. Additional system features such as an automatic wake-up timer, low battery detector, 64 byte TX/RX FIFOs, automatic packet handling, and preamble detection reduce overall current consum ption and allow the use of lower-cost system MCUs. An integrated temperature sensor, general purpose ADC, power- on-reset (POR), and GPIOs further reduce overall system cost and size. The RFM22B/23B’s digital receive architecture features a high-performance ADC and DSP based modem which performs demodulation, filtering, and packet handling for increased flexibility and performance. The direct digital transmit modulation and automatic PA power ramping ensure precise transmit modulation and reduced spectral spreading ensuring compliance with global regulations including FCC, ETSI. An easy-to-use calculator is provided to quickly configure the radio settings, simplifying customer's system design and reducing time to market. Freq uency Range 433/868/915MHz ISM bands Sensitivity = –121 dBm Ou tput power range +20 dBm Max (RFM22B) +13 dBm Max (RFM23B) Low Power Consumption 18.5 mA receive 30 mA @ +13 dBm transmit 85 mA @ +20 dBm transmit Dat a Rate = 0.123 to 256 kbps FSK, GFSK, and OOK modulation Power Supp ly = 1.8 to 3.6 V Ultra low po wer shutdown mode D igital RSSI W ake-up timer Au to-frequency calibration (AFC) Power-on-reset (POR) An tenna diversity and TR switch control C onfigurable packet handler Prea mble detector T X and RX 64 byte FIFOs Lo w battery detector T emperature sensor and 8-bit ADC – 40 to +85 °C temperature range Integ rated voltage regulators F requency hopping capability On-chi p crystal tuning 14-PIN DIP & 16-PIN SMD p ackage Lo w cost Remote control Home security & alarm Te lemetry Persona l data logging T oy control T ire pressure monitoring Wire less PC peripherals Remote meter r eading Remote keyless entry Home au tomation Industrial control Senso r networks Health monitors T ag readers RFM22B/23B Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com V1.0 (–121dBm) extended
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8.2. Microcontroller Clock Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- Electrical S pecifications T able 1. DC Characteristics Pa rameter Symbol Conditions Min Typ Max Units Sup ply Voltage Range V DD 1.8 3.0 3.6 V Power Saving Modes I Sh utdown RC Oscil lator, Main Digital Regulator, and Low Power Digital Regulator OFF —1 5 5 0 n A IS tandby Low Power Digital Regulator ON (Register values retained) and Main Digital Regulator, and RC Oscillator OFF — 450 800 nA ISle ep RC Osci llator and Low Power Digital Regulator ON (Register values retained) and Main Digital Regulator OFF —1 —µ A ISen sor-LBD Mai n Digital Regulator and Low Battery Detector ON, Crystal Oscillator and all other blocks OFF —1 —µ A ISen sor-TS Main Digital Regulator and Temperature Sensor ON, Crystal Oscillator and all other blocks OFF —1 —µ A IRe ady Cryst al Oscillator and Main Digital Regulator ON, all other blocks OFF. Crystal Oscillator buffer disabled — 800 — µA TUNE Mode Current I Tu ne Syn thesizer and regulators enabled — 8.5 — mA RX Mode Current IRX —1 8 . 5 — m A TX Mode Current —RFM22B ITX_+20 txpo TX Mode Current —RFM23B I TX_+13 txpow[2:0] = 110 (+13 dBm) —3 0 — m A ITX_+1 txpow[2:0] = 001 (+1 dBm) —1 8 — m A Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
T able 2. Synthesizer AC Electrical Characteristics Pa rameter Symbol Conditions Min Typ Max Units Synthesizer Frequency Range—RFM22B/23B FSYN 848
888 MHz
F RES-LB 433MHz Band — 156.25 — Hz FRES -HB 868/915MHz Ban d — 312.5 — Hz Reference Frequency Input Level f REF_L V Wh en using external reference signal driving XOUT pin, instead of using crystal. Measured peak-to-peak (VPP) 0.7 — 1.6 V Synthesizer Settling Time tLOCK M easured from exiting Ready mode with XOSC running to any frequency. Including VCO Calibration. —2 0 0— µ s Residual FM FRMS In tegrated over 250 kHz bandwidth (500 Hz lower bound of integration) —2 4 k H z RM S Ph ase Noise L(fM) F = 10 kHz — –80 — dBc/Hz F = 100 kHz — –90 — dBc/Hz F = 1 MHz — –115 — dBc/Hz F = 10 MHz — –130 — dBc/Hz Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com RFM22B/23B 3 453 MHz 901 929 MHz 433MHz band 868MHz band 915MHz band
T able 3. Receiver AC Electrical Characteristics Para meter Symbol Conditions Min Typ Max Units RX Frequency Range—RFM22B/23B FRX RX Sensitiv ity PRX_2 ( BER < 0.1%) (2 kbps, GFSK, BT = 0.5, — –121 — dBm PRX_40 ( BER < 0.1%) (1.2 kbps, FSK, BT=0.5, f = 45kHz) — –114 — dBm PRX_100 ( BER < 0.1%) (100 kbps, GFSK, BT = 0.5, f = 50 kHz) — –104 — dBm PRX_125 ( BER < 0.1%) (125 kbps, GFSK, BT = 0.5, f = 62.5 kHz) — –101 — dBm PRX_OOK ( BER < 0.1%) (4.8 kbps, 350 kHz BW, OOK) —– 1 1 0— d B m (BER < 0.1%) (40 kbps, 400 kHz BW, OOK) — –102 — dBm RX Channel Bandwidth BW 2.6 — 620 kHz BER Variation vs Power Level P RX_RES Up to + 5 dBm Input Level — 0 0.1 ppm RSSI Resolution RESRSSI —± 0 . 5— d B 1-Ch Offset Selectivity C/I1- CH Desired Ref Signal 3 dB above sensitivity, BER < 0.1%. Interferer and desired modu- lated with 40 kbps F = 20 kHz GFSK with BT = 0.5, channel spacing = 150 kHz —– 3 1— d B 2-Ch Offset Selectivity C/I2- CH —– 3 5— d B 3-Ch Offset Selectivity C/I3- CH —– 4 0— d B Blocking at 1 MHz Offset 1MBLOCK Desired Ref Signal 3 dB above sensitivity. Interferer and desired modulated with 40 kbps F = 20 kHz GFSK with BT = 0.5 —– 5 2— d B Blocking at 4 MHz Offset 4MBLOCK —– 5 6— d B Blocking at 8 MHz Offset 8MBLOCK —– 6 3— d B Image Rejection ImREJ Re jection at the image frequency. IF=937 kHz —– 3 0— d B Spurious Emissions POB _RX1 M easured at RX pins — — –54 dBm Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com 433MHz band 868MHz band 915MHz band 848 f = 5k H z ) special crystal is used on the module
T able 4. Transmitter AC Electrical Characteristics Pa rameter Symbol Conditions Min Typ Max Units TX Frequency Range—RFM22B/23B FTX FS K Data Rate DRFSK 0.12 3 — 256 kbps OOK Data Rate DROOK 0.12 3 — 40 kbps Modulation Deviation Δf1 868/915MHz ±0.625 ±320 kHz Δf2 433MHz ±0.625 ±160 kHz Modulation Deviation Resolution Δf RES —0 . 6 2 5— k H z Output Power Range—RFM22B P TX +1 — +20 dBm Output Power Range—RFM23B P TX –8 — +13 dBm TX RF Output Steps PRF _OUT con trolled by txpow[2:0] — 3 — dB TX RF Output Level Variation vs. Temperature PRF_T EMP –40 to +85 C— 2 — d B TX RF Output Level Variation vs. Frequency RF_F REQ M easured across any one frequency band —1— d B Transmit Modulation Filtering B*T Gaussian Filtering Bandwith Time Product —0 . 5— Spurious Emissions P OB- TX1 POUT =+ 1 3d B m , Frequencies <1 GHz —— – 5 4 d B m POB- TX2 1 –12.75 GHz, excluding harmonics — — –54 dBm Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com 433MHz band 868MHz band 915MHz band 848
T able 5. Auxiliary Block Specifications Pa rameter Symbol Conditions Min Typ Max Units Temperature Sensor Accuracy TSA Af ter calibrated via sensor offset register tvoffs[7:0] —0 . 5 — ° C Temperature Sensor Sensitivity TS S —5 — m V / ° C Low Battery Detector Resolution LBD RES —5 0 — m V Low Battery Detector Conversion Time LBD CT —2 5 0 — µ s Microcontroller Clock Output Frequency F MC Config urable to 30 MHz,
15 MHz, 10 MHz, 4 MHz,
3M H z , 2M H z , 1M H z , o r 32.768 kHz 32.768K — 30M Hz General Purpose ADC Resolution ADC EN B —8 — b i t General Purpose ADC Bit Resolution ADC RES —4 — m V / b i t Temp Sensor & General Purpose ADC Conversion Time ADC CT —3 0 5 — µ s
30 MHz XTAL Start-Up time t 30M —6
0 0 — µ s
30 MHz XTAL Cap
RES —9 7 — f F 32 kHz XTAL Start-Up Time t32 k —6 — s e c 32 kHz XTAL Accuracy using 32 kHz XTAL 32K RES — 100 — ppm 32 kHz Accuracy using Internal RC Oscillator 32KRC RES —2 5 0 0 — p p m POR Reset Time tPOR —1 6 — m s Software Reset Time tsof t —1 0 0 — µ s Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
T able 6. Digital IO Specifications (SDO, SDI, SCLK, nSEL, and nIRQ) Para meter Symbol Conditions Min Typ Max Units Rise Time TRISE 0.1 x VDD to 0. 9 x VDD, CL= 5 pF — — 8 ns Fall Time TFA LL 0.9 x VDD to 0.1 x VDD, CL= 5 pF — — 8 ns Input Capacitance CIN —— 1 p F Logic High Level Input Voltage V IH VDD –0 . 6 — — V Logic Low Level Input Voltage V IL —0 . 6 V Input Current IIN 0<VIN< VDD –1 00 — 100 nA Logic High Level Output Voltage VOH IOH< 1 mA source, VDD=1.8 V V DD –0 . 6 — — V Logic Low Level Output Voltage V OL IOL<1 mA sink, VDD=1.8 V — — 0.6 V T able 7. GPIO Specifications (GPIO_0, GPIO_1, and GPIO_2) Pa rameter Symbol Conditions Min Typ Max Units Rise Time TRISE 0.1 x VDD to 0.9 x VDD, CL= 10 pF, DRV<1:0>=HH —— 8 n s Fall Time TFA LL 0.9 x VDD to 0.1 x VDD CL= 10 pF, DRV<1:0>=HH —— 8 n s Input Capacitance CIN —— 1 p F Logic High Level Input Voltage V IH VDD –0 . 6 — V Logic Low Level Input Voltage V IL —— 0 . 6 V Input Current IIN 0< VIN< VDD –10 0 — 100 nA Input Current If Pullup is Activated I INP VIL=0 V 5 — 25 µA Maximum Output Current I OmaxLL DR IOmaxLH DR IOmax HL DR IOmax HH DR Logic High Level Output Voltage V OH IOH< IOmax so urce, VDD=1 .8 V VDD –0 . 6 — — V Logic Low Level Output Voltage V OL IOL< IOmax sink, VDD=1 .8 V —— 0 . 6 V Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
T able 8. Absolute Maximum Ratings Parameter V alue Unit VDD to G ND –0.3, +3.6 V Instantaneous VRF -peak t o GND on TX Output Pin –0.3, +8.0 V Sustained VRF -peak to G ND on TX Output Pin –0.3, +6.5 V Voltage on Digital Control Inputs –0.3, VDD + 0.3 V Voltage on Analog Inputs –0.3, VDD + 0.3 V RX Input Power +10 dBm Operating Temperature Range (Normal crystal is used on the module) T N 0 to +85 C Thermal Impedance JA 30 C/W S torage Temperature Range TSTG –5 5 to +125 C Note: S tresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only and functional operation of the device at or beyond these ratings in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Power Amplifier may be damaged if switched on without proper load or termination connected. TX matching network design will influence TX VRF -peak on TX output pin. Caution: ESD sensitive device. Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com S 0 to +60 C Operating Temperature Range (special crystal is used on the module) T
an ideal solution for battery powered applications. via the standard SPI bus by reading the 64-byte RX FIFO. stream and can be shaped by a Gaussian low-pass filter to reduce unwanted spectral content. "8. Auxiliary Functions"and includes microcontroller clock output, Antenna Diversity, POR, and various interrupts. HopeRF's RFM22B/23B are highly integrated,low cost,433/868/915MHz wireless ISM transceivers module . Figure 1. Voltage regula operating supply voltage range
- RFM23B Application Example MHz m icrocontroller VDD VSS GP GP2 GP3 GP4 100n 100 p C3 C2 VDD_ RF SCLK 161 SDI SDO VDD _DRXn TX RFp GPIO0 GPIO1 VR_DIG nIRQ SDN XOUT nS EL GPIO2 5NC 6AN NC XI N GP5 RF23B Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com RFM23B MODULE
2.1. Operating Modes Th e RFM22B/23B provides several operating modes whic h can be used to optimize the power consumption for a given application. Depending upon the system communication protocol, an optimal trade-off between the radio wake time and power consumption can be achieved. Table 9 summarizes the operating modes of the RFM22B /23B. In general, any given operating mode may be classified as an active mode or a power saving mode. The table indicates which block(s) are enabled (active) in each corresponding mode. With the exception of the SHUTDOWN mode, all can be dynamically selected by sending the appropriate commands over the SPI. An “X” in any cell means that, in the given mode of operation, that block can be independently programmed to be eith er ON or OFF, without noticeably impacting the current consumption. The SPI circuit block includes the SPI interface hardware and the device register space. The 32 kHz OSC block includes the 32.768 kHz RC oscillator or 32.768 kHz crystal oscillator and wake-up timer. AUX (Auxiliary Blocks) includes the temperature sensor, general purpose ADC, and low-battery detector. T able 9. Operating Modes M ode Name Circuit Blocks Digital LDO SPI 32 kHz OSC AUX 30 MHz XTAL PLL PA RX I VDD SHUT DOWN OFF (Register contents lost) OFF OFF OFF OFF OFF OFF OFF 15 nA STANDBY ON (Register
contents
retained) ON OFF OFF OFF OFF OFF OFF 450 nA SLEEP ON ON X OFF OFF OFF OFF 1 µA SENSOR ON X ON OFF OFF OFF OFF 1 µA READY ON X X ON OFF OFF OFF 800 µA TUNING ON X X ON ON OFF OFF 8.5 mA TRANSMIT ON X X ON ON ON OFF 30 mA* RECEIVE ON X X ON ON OFF ON 18.5 mA ote: Using RFM23B at +13 dBm using recommended reference design. Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- Controller Interface 3.1. Serial Peripheral Interface (SPI) Th e RFM22B/23B communicates with the host MCU over a standard 3-wire SPI interface: SCLK, SDI, and nSEL. The host MCU can read data from the device on the SDO output pin. A SPI transaction is a 16-bit sequence which consists of a Read-Write (R/W) selec t bit, followed by a 7-bit address field (ADDR), and an 8-bit data field (DATA) as demonstrated in Figure 3. The 7-bit address field is used to select one of the 128, 8-bit control registers. The R/W select bit determines whether the SPI transaction is a read or write transaction. If R/W = 1 it signifies a WRITE transaction, while R /W = 0 signifies a READ transaction. The contents (ADDR or DATA) are latched into the RFM22B/23B every eight clock cycles. The timing parame ters for the SPI interface are shown in Table 10. The SCLK rate is flexible with a maximum rate of 10 MHz. Figure 3. SPI Timing T o read back data from the RFM22B/23B, the R/W bit must be set to 0 followed by the 7-bit address of the register from which to read. The 8 bit DATA field following the 7-bit ADDR field is ignored on the SDI pin when R/W = 0. The next eight negative edge transitions of the SCLK signal will clock out the contents of the selected register. The data read from the selected regi ster will be available on the SDO output pin. The READ function is shown in Figure 4. After the READ function is completed the SDO pin will rema in at either a logic 1 or logic 0 state depending on the last data bit clocked out (D0). When nSEL goes high the SDO output pin will be pulled high by internal pullup. T able 10. Serial Interface Timing Parameters Symbol Parameter Min (nsec) Diagram tCH Clock h igh time 40 tCL Cloc k low time 40 tDS Da ta setup time 20 tDH Da ta hold time 20 tDD Output data delay time 20 tEN Outpu t enable time 20 tDE Output disab le time 50 tSS Select setup time tSH Select hold time tSW Se lect high period 80 nSEL SCLK SDI MS B LSB A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 A4 xx xx A3 RW A7A6 A5 RW Da taAddre ss SD I SCLK SD O n SEL tCL tCH tDS tDH tDDtSS tEN tSH tDE tSW Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
latched into the RFM22B/23B every eight SCLK cycles. Figure 6. SPI Timing—Burst Read Mode
mode as well as the current consumption of each mode. Table 11. Operating Modes Response Time
2.1. SHUTDOWN State The SHUTDOWN state is the lowest current consumption state of the device with nominally less than 15 nA of current consumption. The shutdown state may be entere d by driving the SDN pin high. The SDN pin should be held low in all states e xcept the SHUTDOWN state. In the SHUTDOWN state, the contents of the registers are lost and there is no SPI access. When the chip is connected to the power supply, a POR will be initiated after the falling edge of SDN. 3.2.2. IDLE State There are five different modes in the IDLE state which may be selected by "Register 07h. Operating Mode and Function Control 1". All modes have a tradeoff between current consumption and response time to TX/RX mode. This tradeoff is shown in Table 11. After the POR event, SWRESET, or exiting from the SHUTDOWN state the chip will default to the IDLE-READY mode. After a POR event the in terrupt registers must be read to properly enter the SLEEP , SENSOR, or STANDBY mode and to control the 32 kHz clock correctly. 3.2.2.1. STANDBY Mode STANDBY mode has the lowest current consumption of th e five IDLE states with only the LPLDO enabled to maintain the register values. In this mode the regist ers can be accessed in both read and write mode. The STANDBY mode can be entered by writ ing 0h to "Register 07h. Operating Mode and Function Control 1". If an interrupt has occurred (i.e., the nIRQ pin = 0) the interr upt registers must be read to achieve the minimum current consumption. Additionally, the ADC should not be selected as an input to th e GPIO in this mode as it will cause excess current consumption. 3.2.2.2. SLEEP Mode In SLEEP mode the LPLDO is enabled along with the Wake -Up-Timer, which can be used to accurately wake-up the radio at specified intervals. See "8.6. Wake-U p Timer and 32 kHz Clock Source for more on the Wake -Up-Timer. SLEEP mode is entered by setting enwt = 1 (40h) in "Regi ster 07h. Operating Mode and Function Control 1". If an interrupt has occurred (i.e., the nIRQ pin = 0) the interrupt registers must be read to achieve the minimum current consumption. Also, the ADC should not be selected as an input to the GPIO in this mode as it will cause excess current consumption. 3.2.2.3. SENSOR Mode In SENSOR mode either the Low Battery Detector, Temperature Sensor, or both may be enabled in addition to the LPLDO and Wake-Up-Timer. The Low Battery Detector can be enabled by setting enlbd = 1 in "Register 07h. Detector" for more information on these featur es. If an interrupt has occurred (i.e., the nIRQ pin = 0) the interrupt registers must be read to achieve the minimum current consumption. 3.2.2.4. READY Mode READY Mode is designed to give a fast transition time to TX mode with reasonable current consumption. In this mode the Crystal oscillator remains enabled reducing the time required to switch to TX or RX mode by eliminating the crystal start-up time. READY mode is entered by setting xton = 1 in "Register 07h. Operating Mode and Function Control 1". To achieve the lowest current co nsumption state the crystal oscillator buffer should be disabled in “Register 62h. Crystal Oscillator Control and Test.” To exit READY mode, bufovr (bit 1) of this register must be set back to 0. 3.2.2.5. TUNE Mode In TUNE mode the PLL remains enabled in addition to the other blocks enabled in the IDLE modes. This will give the fastest response to TX mode as the PLL will re main locked but it results in the highest current consumption. This mode of operation is designed for frequency hopp ing spread spectrum syste ms (FHSS). TUNE mode is entered by setting pllon = 1 in "Register 07h. Operating Mode and Function Control 1". It is not necessary to set xton to 1 for this mode, the internal state machine automatically enables the crystal oscillator. Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com information
2.3. TX State The TX state may be entered from any of the IDLE modes when the txon bit is set to 1 in "Register 07h. Operating Mode and Function Control 1". A built-in sequencer takes care of all the actions re quired to transition between states from enabling the crystal oscillator to ramping up the PA. The following sequence of events will occur automatically when going from STANDBY mode to TX mode by setting the txon bit. 1. Enable the main digital LDO and the Analog LDOs. 2. Start up crystal oscillator and wait until ready (controlled by an internal timer). 3. Enable PLL. 4. Calibrate VCO (this action is skipped when the vcocal bit is “0”, default value is “1”). 5. Wait until PLL settles to required transmit frequency (controlled by an internal timer). 6. Activate power amplifier and wait until power ramping is completed (controlled by an internal timer). 7. Transmit packet. Steps in this sequence may be eliminated depending on which IDLE mode the chip is configured to prior to setting the txon bit. By default, the VCO and PLL are calibrated every time the PLL is enabled. 3.2.4. RX State The RX state may be entered from any of the IDLE modes when the rxon bit is set to 1 in "Register 07h. Operating Mode and Function Control 1". A built-in sequencer takes ca re of all the actions required to transition from one of the IDLE modes to the RX state. The following sequence of events will occur automatically to get the chip into RX mode when going from STANDBY mode to RX mode by setting the rxon bit: 1. Enable the main digital LDO and the Analog LDOs. 2. Start up crystal oscillator and wait until ready (controlled by an internal timer). 3. Enable PLL. 4. Calibrate VCO (this action is skipped when the vcocal bit is “0”, default value is “1”). 5. Wait until PLL settles to required receive frequency (controlled by an internal timer). 6. Enable receive circuits: LNA, mixers, and ADC. 7. Enable receive mode in the digital modem. Depending on the configuration of the radio all or some of the following functions will be performed automatically by the digital modem: AGC, AFC (optional), update status registers, bit synchronization, packet handling (optional) including sync word, header check, and CRC. 3.2.5. Device Status The operational status of the chip can be read from "Register 02h. Device Status". Add R/W Function/Description D 7 D6 D5 D4 D3 D2 D1 D0 POR Def.
02 R Device Status ffovfl ffunfl rxffem headerr freqerr cps[1] cps[0] —
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3.3. Interrup ts Th e RFM22B/23B is capable of generating an interrupt sign al when certain events occur. The chip notifies the microcontroller that an interrupt event has occurred by setting the nIRQ output pin LOW = 0. This interrupt signal will be generated when any one (or more) of the interrupt events (corresponding to the Interrupt Status bits) shown below occur. The nIRQ pin will remain low until the microcontroller reads the Interrupt Status Register(s) (Registers 03h–04h) containing the active Interrupt Status bit. The nIRQ output signal will then be reset until the next change in status is detected. The interrupts must be enabled by the corresponding enable bit in the Interrupt Enable Registers (Registers 05h–06h). All enabled interrupt bits will be cleare d when the microcontroller reads the interrupt status register. If the interrupt is not enabled when the event occurs it will not trigger the nIRQ pin, but the status may still be read at anytime in the Interrupt Status registers. Add R/W Function/Descript ion D 7 D6 D5 D4 D3 D2 D1 D0 POR Def.
03 R Interrupt Status 1 ifferr itxffafull itxffaem irxffafull iext ipksent ipkvalid icrcerror —
04 R Interrupt Status 2 iswdet ipreaval ipreainval irssi iwut ilbd ichiprdy ipor —
05 R/W Interrupt Enable 1 enfferr entxffafull entxffa em enrxffafull enext enpksent enpkvalid encrcerror 00h
06 R/W Interrupt Enable 2 enswdet enpreaval en preainval enrssi enwut enlbd enchiprdy enpor 01h
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program the desired mode, and the internal sequencer will properly transition the part from its current mode. Figure 9. RX Timing
3.5. Freq uency Control For calculating the nec essary frequency register settings it is re commended that customers use the HOPERF Register Calculator worksheet (in Microsoft Excel) available on These methods offer a simple method to quickly determi ne the correct settings based on the application requirements. The following information can be used to calculated these values manually. 3.5.1. Frequency Programming In order to receive or transmit an RF signal, the desired channel frequency, f car rier, m ust be programmed into the RFM22B/23B. The carrier frequency is generated by a Fractional-N Synthesizer, using 10 MHz both as the reference frequency and the clock of the (3 rd or der) ΔΣ modulator. This modulator uses modulo 64000 accumulators. This design was made to obtain the desi red frequency resolution of the synthesizer. The overall division ratio of the feedback loop consist of an integer part (N) and a fractional part (F).In a generic sense, the output frequency of the synthesizer is as follows: The fractional part (F) is determined by three differ ent values, Carrier Frequency (fc[15:0]), Frequency Offset (fo[8:0]), and Frequency Deviation (fd[7:0]). Due to the fi ne resolution and high loop bandwidth of the synthesizer, FSK modulation is applied inside the loop and is done by varying F according to the incoming data; this is discussed further in "3.5.4. Frequency Deviation" Also, a fixed offset can be added to fine-tune the carrier frequency and counteract crystal tolerance errors. For simplicity assume that only the fc[15:0] register will determine the fractional component. The equation for selection of the carrier frequency is shown below: The integer part (N) is determined by fb[4:0]. Additio nally, the output frequency can be halved by connecting a ÷2 divider to the output. This divider is not inside the loop and is controlled by the hbsel bit in "Register 75h. Frequency Band Select." This effect ively partitions the entire 240–960 MHz frequency range into two separate bands: High Band (HB) for hbsel = 1, and Low Band (LB) for hbsel = 0. The valid range of fb[4:0] is from 0 to 23. If a higher value is written into the regist er, it will default to a value of 23. The integer part has a fixed offset of 24 added to it as shown in the formula above. Table 12 demonstrates the selection of fb[4:0] for the corresponding frequency band. After selection of the fb (N) the fractional component may be solved with the following equation: fb and fc are the actual numbers stored in the corresponding registers. Add R/W Function/Description D6 D5 D4 D3 D2 D1 D0 POR Def.
73 R/W Frequency Offset 1 fo[7] fo[6] fo[5] fo[4] fo[3] fo[2] fo[1] fo[0] 00h
74 R/W Frequency Offset 2 fo[9] fo[8] 00h
75 R/W Frequency Band Select sbsel hbsel fb[4] fb[3] fb[2] fb[1] fb[0] 35h
76 R/W Nominal Carrier
fc[15] fc[14] fc[13] fc[12] fc[11] fc[10] fc[9] fc[8] BBh
77 R/W Nominal Carrier
fc[7] fc[6] fc[5] fc[4] fc[3] fc[2] fc[1] fc[0] 80h ( 10 F N MHzfOUT ( ) 1 ( 10F NhbselMHzfcarrier )64000 0 : 15 [24 ] 0 : 4 [ ( * ) 1 ( * 10fcfbhbselMHzfTX 64000 ffc TX Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com the product website.
The chip will automatically s hift the frequency of the Synthesizer down by 937.5 kHz (30 MHz ÷ 32) to achieve the correct Intermediate Frequency (IF) when RX mode is entered. Low-side injection is used in the RX Mixing architecture; therefore, no frequency reprogramming is required when using the same TX frequency and switching between RX/TX modes. T able 12. Frequency Band Selection fb [4:0] Value N Frequency Band hbsel=0 hbsel=1 0 24 240–249.9 MHz 480–499.9 MHz 1 25 250–259.9 MHz 500–519.9 MHz 2 26 260–269.9 MHz 520–539.9 MHz 3 27 270–279.9 MHz 540–559.9 MHz 4 28 280–289.9 MHz 560–579.9 MHz 5 29 290–299.9 MHz 580–599.9 MHz 6 30 300–309.9 MHz 600–619.9 MHz 7 31 310–319.9 MHz 620–639.9 MHz 8 32 320–329.9 MHz 640–659.9 MHz 9 33 330–339.9 MHz 660–679.9 MHz 10 34 340–349.9 MHz 680–699.9 MHz 11 35 350–359.9 MHz 700–719.9 MHz 12 36 360–369.9 MHz 720–739.9 MHz 13 37 370–379.9 MHz 740–759.9 MHz 14 38 380–389.9 MHz 760–779.9 MHz 15 39 390–399.9 MHz 780–799.9 MHz 16 40 400–409.9 MHz 800–819.9 MHz 17 41 410–419.9 MHz 820–839.9 MHz 18 42 420–429.9 MHz 840–859.9 MHz 19 43 430–439.9 MHz 860–879.9 MHz 20 44 440–449.9 MHz 880–899.9 MHz 21 45 450–459.9 MHz 900–919.9 MHz 22 46 460–469.9 MHz 920–939.9 MHz 23 47 470–479.9 MHz 940–960 MHz Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
.5.2. Easy Frequency Programming for FHSS While Registers 73h–77h may be used to program the carrie r frequency of the RFM22B/23B , it is often easier to think in terms of “channels” or “channel numbers” rather than an absolute frequency value in Hz. Also, there may be some timing-critical applications (such as for Frequen cy Hopping Systems) in whic h it is desirable to change frequency by programming a single register. Once the chan nel step size is set, the frequency may be changed by a single register corresponding to the channel number. A nominal frequency is first set using Registers 73h–77h, as described above. Registers 79h and 7Ah are then used to set a channel step size and channel number, relative to the nominal setting. The Frequency Hopping Step Size (fhs[7:0]) is set in increments of 10 kHz with a maximum channel step size of 2.56 MHz. The Frequency Hopping Channel Select Register then selects channels based on multiples of the step size. For example, if the nominal frequency is set to 900 MHz using Registers 73h–77h, the channel step size is set to 1 MHz using "Register 7Ah. Frequency Hopping Step Si ze," and "Register 79h. Frequency Hopping Channel Select" is set to 5d, the resulting carrier frequency would be 905 MHz. Once the nominal frequency and channel step size are programmed in the registers, it is only necessary to program the fhch[7:0] register in order to change the frequency. 3.5.3. Automatic State Transition for Frequency Change If registers 79h or 7Ah are changed in either TX or mode, the state mach ine will automatically transition the chip back to TUNE, change the frequency, and automatically go back to either TX or RX. This feature is useful to reduce the number of SPI commands required in a Frequency Ho pping System. This in turn reduces microcontroller activity, reducing current consumption. The exception to this is during TX FIFO mode. If a frequency change is initiated during a TX packet, then the part will complete the current TX packet and will only change the frequency for subsequent packets. 3.5.4. Frequency Deviation The peak frequency deviation is configurable from ±0.625 to ±320 kHz. The Frequency Deviation ( Δf) is controlled by the Frequency Deviation Register (fd), address 71 and 72h, and is independent of the carrier frequency setting. When enabled, regardless of the setting of the hbsel bit (high band or low band), the resolution of the frequency deviation will remain in increm ents of 625 Hz. When using frequency modu lation the carrier frequency will deviate from the nominal center channel carrier frequency by ±Δf: Add R/W Function/Description D 7 D6 D5 D4 D3 D2 D1 D0 POR Def.
79 R/W Frequency Hopping Channel
fhch[7] fhch[6] fhch[5 ] fhch[4] fhch[3] fhch[2] fhch[1] fhch[0] 00h 7A R/W Frequency Hopping Step Size fhs[7] fhs[6] fhs[5] fhs[4] fh s[3] fhs[2] fhs[1] fhs[0] 00h 10 ] 0 : 7 [ ( ] 0 : 7 [kHzfhchfhs FnomFcarrier Hz ffd 625] 0 : 8 [ f peak deviation= Hzfd f 625 ] 0 : 8 [ Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- Frequency Deviation Th e previous equation should be used to calculate t he desired frequency deviation. If desired, frequency modulation may also be disabled in order to obtain an unmodulated carrier signal at the channel center frequency; see "4.1. Modulation Type" for further details. Add R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def. 71 R/W Modulation Mode Control 2 trclk[1] trclk[0 ] dtmod[1] dtmod[0] eninv fd[8] modtyp[1] modtyp[0] 00h
72 R/W Frequency Deviation fd[7] fd[6] f d[5] fd[4] fd[3] fd[2] fd[1] fd[0] 20h
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5.5. Frequency Offset Adjustment When the AFC is disabled the frequency offset can be adjust ed manually by fo[9:0] in registers 73h and 74h. It is not possible to have both AFC and offset as internally they share the same register. The frequency offset adjustment and the AFC both are implemented by shifting the Synthesizer Local Oscillator frequency. This register is a signed register so in order to ge t a negative offset it is necessary to take the twos complement of the positive offset number. The offset can be calculated by the following: The adjustment range in high band is ±160 kHz and in low band it is ±80 kHz. For example to compute an offset of +50 kHz in high band mode fo[9:0] should be set to 0A0h. For an offset of –50 kHz in high band mode the fo[9:0] register should be set to 360h. 3.5.6. Automatic Frequency Control (AFC) All AFC settings can be easily obtained from the settings calculator. This is the recommended method to program all AFC settings. This section is intended to describe the operation of the AFC in more detail to help understand the trade-offs of using AFC.The receiver supports automati c frequency control (AFC) to compensate for frequency differences between the transmitter and receiver reference frequencies. These differences can be caused by the absolute accuracy and temperature dependencies of the reference crystals. Due to frequency offset compensation in the modem, the receiver is tolerant to frequency offs ets up to 0.25 times the IF bandwidth when the AFC is disabled. When the AFC is enabled, the received signal will be centered in the pass-band of the IF filter, providing optimal sensitivity and selectivity over a wider range of frequency offsets up to 0.35 times the IF bandwidth. The trade-off of receiver sensitivity (at 1% PER) versus carrier offset and the impact of AFC are illustrated in Figure 11. Figure 11. Sensitivity at 1% PER vs. Carrier Frequency Offset Add R/W Function/Description D
7 D6 D5 D4 D3 D2 D1 D0 POR
Def.
73 R/W Frequency Offset fo[7] fo[6] fo[5] fo[4] fo[3] fo[2] fo[1] fo[0] 00h
74 R/W Frequency Offset fo[9] fo[8] 00h
0 : 9 [ ) 1 ( 25 . 156fohbsel HzsetDesiredOff 1 ( 25 . 156] 0 : 9 [ hbsel Hz setDesiredOfffo Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
n AFC is enabled, the preamble length needs to be long enough to settle the AFC. In general, one byte of preamble is sufficient to settle the AFC. Disabling the AFC allows the preamble to be shortened from 40 bits to 32 bits. Note that with the AFC disabled, the preamble leng th must still be long enough to settle the receiver and to detect the preamble (see "6.7. Preamble Length" . The AFC corrects the detected frequency offset by changing the frequency of the Fracti onal-N PLL. When the pr eamble is detected, the AFC will freeze for the remainder of the packet. In multi-packet mode the AFC is reset at the end of every packet and will re-acquire the frequency offset for the next packet. The AFC loop in cludes a bandwidth limiting mechanism improving the rejection of out of band signals. When the AFC loop is enabled, its pull-in-range is determined by the bandwidth limiter value (AFCLimiter) which is located in register 2Ah. AFC_pull_in_range = ±AFCLimiter[7:0] x (hbsel+1) x 625 Hz The AFC Limiter register is an unsigned register and its value can be obtained from the HOPERF Register Calculator spreadsheet. The amount of error correction feedback to the Fractional-N PLL before the preamble is detected is controlled from afcgearh[2:0]. The default value 000 relates to a feedback of 100% from the measured frequency error and is advised for most applications. Every bit added will half the feedback but will require a longer preamble to settle. The AFC operates as follows. The frequency error of the incoming signal is measur ed over a period of two bit times, after which it corrects the local oscillator via the Fractional-N PLL. After this correction, some time is allowed to settle the Fractional-N PLL to the new frequency bef ore the next frequency error is measured. The duration of the AFC cycle before the preamble is detected can be programmed with shwait[2:0]. It is advised to use the default value 001, which sets the AFC cycle to 4 bit times (2 for measurement and 2 for settling). If shwait[2:0] is programmed to 3'b000, there is no AFC correction output. It is advised to use the default value 001, which sets the AFC cycle to 4 bit times (2 for measurement and 2 for settling). The AFC correction value may be read from register 2Bh. The value read can be converted to kHz with the following formula: AFC Correction = 156.25Hz x (hbsel +1) x afc_corr[7: 0] Frequency Correction RX TX AFC disabled Freq Offset R egister Freq Offset Register AFC enabled AFC Freq Offset Register Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
5.7. TX Data Rate Generator The data rate is configurable between 0.123–256 kbps. For data rates below 30 kbps the ”txdtrtscale” bit in register 70h should be set to 1. When higher data rates are used this bit should be set to 0. The TX date rate is determined by the following formula in kbps: For data rates higher than 100 kbps, Register 58h should be changed from its default of 80h to C0h. Non-optimal modulation and increased eye closure will result if this setting is not made for data rates higher than 100 kbps. The txdr register is only applicable to TX mode and does not need to be programmed for RX mode. The RX bandwidth which is partly determined from the data rate is programmed separately. Add R/W Function/Description D6 D5 D4 D3 D2 D1 D0 POR Def. 6E R/W TX Data Rate 1 txdr[15] txdr[14] txdr[13] txdr[12] txdr[11] txdr[10] txdr[9] txdr[8] 0Ah 6F R/W TX Data Rate 0 txdr[7] txdr[6] txdr[ 5] txdr[4] txdr[3] txdr[2] txdr[1] txdr[0] 3Dh DR _TX (kbps) txdr 15:0 1 MHz txdr[1 5:0] DR_TX(kbps) 2 1 6 5 txdtrtscale+ Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- Modulation Options 4.1. Modulation T ype Th e RFM22B/23B supports three different modulation options: Gaussian Frequency Shift Keying (GFSK), Frequency Shift Keying (FSK), and On-Off Keying (O OK). GFSK is the recommended modulation type as it provides the best performance and cleanest modulation spectrum. Figure 12 demonstrates the difference between FSK and GFSK for a Data Rate of 64 kbps. The time domain plots demonstrate the effects of the Gaussian filtering. The frequency domain plots demonstrate the spectral benefit of GFSK over FSK. The type of modulation is selected with the modtyp[1:0] bits in "Register 71h. Modulation Mode Cont rol 2". Note that it is also possible to obtain an unmodulated carrier signal by setting modtyp[1:0] = 00. Fig ure 12. FSK vs GFSK Spectrums mod typ[1:0] Modulation Source
00 Unmodulated Carrier
01 OOK
10 FSK
11 GFSK (enable TX Data CLK when direct mode is used)
TX Modulation Time Domain Waveforms -- FSK vs. GFSK -1.0 -0.5 0.0 0.5 1.0 -1.5 1.5 SigData_FSK[0,::] 100 150 200 250 300 350 400 45005 00 -0.5 0.0 0.5 -1.0 1.0 time, usec SigData_GFSK[0,::] TX Modulation Spectrum -- FSK vs GFSK (Continuous PRBS) -80 -60 -40 -100 -20 ModSpectrum_FSK -200 -150 -100 -50 0 50 100 150 200-250 250 -80 -60 -40 -100 -20 freq, KHz ModSpectrum_GFSK DataRate 64000.0 TxDev 32000.0 BT_Filter 0.5 ModIndex 1.0 Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
4.2. Modulation Dat a Source Th e RFM22B/23B may be configured to obtain its modulation data from one of three different sources: FIFO mode, Direct Mode, and from a PN9 mode. In Direct Mode, the TX modulation data may be obtained from several different input pins. These options are set through the dtm od[1:0] field in "Register 7 1h. Modulation Mode Control 2". 4.2.1. FIFO Mode In FIFO mode, the transmit and receive data is stored in integrated FIFO register memory. The FIFOs are accessed via "Register 7Fh. FIFO Access," and are most efficiently accessed with burst read/write operation as discussed in "3.1. Serial Peripheral Interface (SPI)" . In TX mode, the data bytes stored in FIFO memory ar e "packaged" together with other fields and bytes of information to construct the final transmit packet structure. These other potential fields include the Preamble, Sync word, Header, CRC checksum, etc. The configuration of the packet struct ure in TX mode is determined by the Automatic Packet Handler (if enabled), in conjunction with a variety of Packet Handler Registers (see Table 13). If the Automatic Packet Handle r is disabled, the entire desired pack et structure should be loaded into FIFO memory; no other fields (such as Preamble or Sync word are automatically added to the bytes stored in FIFO memory). For further information on the configuration of the FIFOs for a specific application or packet size, see "6. Data Handling and Packet Handler" . In RX mode, only the bytes of the received packet struct ure that are considered to be "data bytes" are stored in FIFO memory. Which bytes of the received packet are considered "data bytes" is determined by the Automatic Packet Handler (if enabled), in conjunction with the Pack et Handler Registers (see Table 13 ). If the Automatic Packet Handler is disabled, all bytes following the Sync word are considered data bytes and are stored in FIFO memory. Thus, even if Automatic Packet Handling operation is not desired, the preamble detection threshold and Sync word still need to be programmed so that th e RX Modem knows when to start filling data into the FIFO. When the FIFO is being used in RX mode, all of the received data may still be observed directly (in real- time) by properly programming a GPIO pin as the RXDATA ou tput pin; this can be quite useful during application development. When in FIFO mode, the chip will automatically exit the TX or RX State when either the ipksent or ipkvalid interrupt occurs. The chip will return to the ID LE mode state progr ammed in "Register 07h. Op erating Mode and Function Control 1". For example, the chip may be placed into TX mode by setting the txon bit, but with the pllon bit additionally set. The chip will transmit all of the contents of the FIFO and the ipksent interrupt will occur. When this interrupt event occurs, the chip will clear the txon bit and return to TUNE mode, as indicated by the set state of the pllon bit. If no other bits are additionally set in register 07h (besides txon initially), then the chip will return to the STANDBY state. In RX mode, the rxon bit will be cleared if ipkvalid occurs and the rxmpk bit (RX Multi-Packet bit, SPI Register 08h bit [4]) is not set. When the rxmpk bit is set, the part will not exit the RX state after successfully receiving a packet, but will remain in RX mode. The micr ocontroller will need to decide on the appropriat e subsequent action, depending upon information such as an interrupt generated by CRC, packet valid, or preamble detect. Add R/W Function/Description D6 D5 D4 D3 D2 D1 D0 POR Def.
71 R/W Modulation Mode
trclk[1] trclk[0] dtmod[1] dtmod[0] eninv fd[8] modtyp[1] modtyp[0] 00h d tmod[1:0] Data Source
00 Direct Mode using TX/RX Data via GP IO pin (GPIO configuration required)
01 Direct Mode using TX/RX Data via SDI pin (only when nSEL is high)
10 FIFO Mode
11 PN9 (internally generated)
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2.2. Direct Mode For legacy systems that perform packet handling within an MCU or other baseband chip, it may not be desirable to use the FIFO. For this scenario, a Direct Mode is provided which bypasses the FIFOs entirely. In TX direct mode, the TX modulation data is applied to an input pin of the chip and processed in "real time" (i.e., not stored in a register for transmission at a later time). A variety of pins may be configured for use as the TX Data input function. Furthermore, an additional pin may be required for a TX Clock output function if GFSK modulation is desired (only the TX Data input pin is required for FSK). Two options for the source of the TX Data are available in the dtmod[1:0] field, and various configurations for the source of the TX Data Clock may be selected through the trclk[1:0] field. The eninv bit in SPI Register 71h will in vert the TX Data; this is most likely useful for diagnostic and testing purposes. In RX direct mode, the RX Data and RX Clock can be pr ogrammed for direct (real-time) output to GPIO pins. The microcontroller may then process the RX data without usin g the FIFO or packet handler functions of the RFIC. In RX direct mode, the chip must still acquire bit timing during the Preamble, an d thus the preamble detection threshold (SPI Register 35h) must still be programmed. Once the preamble is detected, certain bit timing functions within the RX Modem change their operation for optimized pe rformance over the remainder of the packet. It is not required that a Sync word be present in the packet in RX Direct mode; however, if the Sync word is absent then the skipsyn bit in SPI Register 33h must be set, or else the bit timing and trac king function within the RX Modem will not be configured for optimum performance. 4.2.2.1. Direct Synchronous Mode In TX direct mode, the chip may be configured for synchronous or asynchronous modes of modulation. In direct synchronous mode, the RFIC is configured to provide a TX Clock signal as an output to the external device that is providing the TX Data stream. This TX Clock signal is a square wave with a frequency equal to the programmed data rate. The external modulation so urce (e.g., MCU) must a ccept this TX Clock signal as an input and respond by providing one bit of TX Data back to the RFIC, syn chronous with one edge of the TX Clock signal. In this fashion, the rate of the TX Data input stream from the external source is controlled by the programmed data rate of the RFIC; no TX Data bits are made available at the inpu t of the RFIC until requested by another cycle of the TX Clock signal. The TX Data bits supplied by the external source are transmitted directly in real-time (i.e., not stored internally for later transmission). All modulation types (FSK/GFSK/ OOK) are valid in TX direct synchronous mode. As will be discussed in the next section, there are limits on modulation types in TX direct asynchronous mode. 4.2.2.2. Direct Asynchronous Mode In TX direct asynchronous mode, the RFIC no longer cont rols the data rate of the TX Data input stream. Instead, the data rate is controlled only by the external TX Data source; the RFIC simply accepts the data applied to its TX Data input pin, at whatever rate it is supplied. This means that there is no longer a need for a TX Clock output signal from the RFIC, as there is no synchronous "hand shaking" between the RFIC a nd the external data source. The TX Data bits supplied by the external source are transm itted directly in real-time (i.e., not stored internally for later transmission). It is not necessary to program the data rate parameter wh en operating in TX direct asynchronous mode. The chip still internally samples the in coming TX Data stream to determine when edge transitions occu r; however, rather than sampling the data at a pre-programmed data rate, the chip now internally samples the incoming TX Data stream at its maximum possible oversampling rate. This allows the chip to accurately determine the timing of the bit edge transitions without prior knowledge of the data rate. (Of course, it is still necessary to program the desired peak frequency deviation.) trclk[1:0] TX/RX Data Clock Configuration
00 No TX Clock (only for FSK)
01 TX/RX Data Clock is available via GPIO (GPIO needs programming accordingly as well)
10 TX/RX Data Clock is available via SDO pin (only when nSEL is high)
11 TX/RX Data Clock is available via the nIRQ pin
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cannot determine the appropriate Gaussian lowpass filter function to apply to the incoming data. One advantage of this mode that it saves a microcontroller pin because no TX Clock output function is required.
- Direct Synchronous Mode Example
Figure 14. Direct Asynchronous Mode Example or 06h, then the nIRQ pin can also be used as the TX/RX data clock. rect asynchronous FSK modulation.
and transmitted. In RX mode it will be the received demodulated data. Figure 15 demonstrates using SDI and SDO as the TX/RX data and clock: Figure 15. Microcontroller Connections If the SDO pin is not used for data clock then it may be programmed to be the interrupt function (nIRQ) by programming Reg 0Eh bit 3. 4.2.3. PN9 Mode In this mode the TX Data is generated internally using a pseudorandom (PN9 sequence) bit generator. The primary purpose of this mode is for use as a test mode to observe the modulated spectrum without having to provide data. nS EL SDI SDO S PI input don’t care SPI input TX on command TX mode MOD input TX off command SPI input don’t care RX on command RX mode RX off command Data outputSPI input SPI input SPI output SPI output SPI output SPI output SPI outputdon’t care don’t careData CLK Output Data CLK Output Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
. Internal Functional Blocks Th is section provides an overview some of the key blocks of the internal radio architecture. 5.1. RX LNA T he LNA provides gain with a noise figure low enough to suppress the noise of t he following stages. which is controlled by the analog gain control (AGC) algo The AGC algorithm adjusts the gain of the LNA andPGA so the receiver can handle signal levels from For the RFM23B, The direct tie is used, The lna_sw bit in “Register 6Dh. TX Power” must be set. 5.2. RX I-Q Mixer Th e output of the LNA is fed internally to the input of the receive mixer. The receive mixer is implemented as an I-Q mixer that provides both I and Q channel outputs to the programmable gain amplifier. The mixer consists of two double-balanced mixers whose RF inputs are driven in parallel, local oscillator (LO) inputs are driven in quadrature, and separate I and Q I nt ermediate Fre quency (IF) outputs drive the prog rammable gain amplifier. The receive LO signal is supplied by an integrated VCO and PLL syn thesizer operating between 240–960 MHz. The necessary quadrature LO signals are derived from the divider at the VCO output. 5.3. Pr ogrammable Gain Amplifier Th e programmable gain amplifier (PGA) provides the necessary gain to boost the signal level into the dynamic range of the ADC. The PGA must also have enough gain switching to allow for large input signals to ensure a linear RSSI range up to –20 dBm. The PGA has steps of 3 dB which are controlled by the AGC algorithm in the digital modem. 5.4. ADC Th e amplified IQ IF signals are digitized using an Analog -to-Digital Converter (ADC), which allows for low current consumption and high dynamic range. The bandpass response of the ADC provides exceptional rejection of out of band blockers. 5.5. Digit al Modem Using high-performance ADC s allows channel filtering, image rejection, and demodulation to be performed in the digital domain, resulting in reduced area while increa sing flexibility. The digital modem performs the following functions: Channel s election filter TX mo dulation RX dem odulation AGC Pr eamble detector Invalid preamble detector Rad io signal strength indicator (RSSI) Automatic frequency compensation (AFC) Packet han dling including EZMAC® fe atures Cyc lic redundancy check (CRC) The digital channel filter and demodulator are optimized for ultra low power consumption and are highly configurable. Supported modulation types are GFSK, F SK, and OOK. The channel filter can be configured to support bandwidths ranging from 620 kHz down to 2.6 kHz . A large variety of data rates are supported ranging from 0.123 up to 256 kbps. The AGC algorithm is implement ed digitally using an advanced control loop optimized for fast response time. Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com T he LNA has one step of gain control rithm. om sensitivity to +5 dBm with optimal performance.
The configurable preamble detector is used to improve the relia bility of the sync-word de tection. The sync-word detector is only enabled when a valid preamble is detected, significantly reducing the probability of false detection. The received signal strength indicato r (RSSI) provides a measure of the si gnal strength received on the tuned channel. The resolution of the RSSI is 0.5 dB. This high resolution RSSI enables accurate channel power measurements for clear channel assessment (CCA), carrier sense (CS), and listen before talk (LBT) functionality. Frequency mistuning caused by crystal inaccuracies c an be compensated by enabling the digital automatic frequency control (AFC) in receive mode. A comprehensive progra mmable packet handler including key features of HOPERF’ EZMAC is integrated to create a variety of communication topologies ranging from peer-to-peer networks to mesh networks. The extensive programmability of the packet header allows for advanced packet filtering which in turn enables a mix of broadcast, group, and point-to-point communication. A wireless communication channel can be corrupted by no ise and interference, and it is therefore important to know if the received data is free of errors. A cyclic redundancy check (CRC) is us ed to detect the presence of erroneous bits in each packet. A CRC is computed an d appended at the end of each transmitted packet and verified by the receiver to confirm that no errors ha ve occurred. The packet handler and CRC can significantly reduce the load on the system microcontroller allowing for a simpler and cheaper microcontroller. The digital modem includes the TX modulator which conver ts the TX data bits into the corresponding stream of digital modulation values to be summed with the fractio nal input to the sigma-delta modulator. This modulation approach results in highly accurate resolution of the frequency deviation. A Gaussian filter is implemented to support GFSK, considerably reducing the energy in th e adjacent channels. The default bandwidth-time product (BT) is 0.5 for all programmed data rates, but it may not be adjusted to other values. 5.6. Synthesizer An integrated Sigma Delta (ΣΔ) Fractional-N PLL synthesizer capable of operating from 240–960 MHz is provided Using a ΣΔ synthesizer has many advantages; it provides flexibility in frequency, and channel spacing. The transmit modulation is applied directly to the loop in the digital domain through the fractional divider which results in very precise accuracy and control over the transmit deviation. Depending on the part, the PLL and - modulator scheme is designed to support any desired frequency and channel spacing in the range from 240–960 MHz with a frequency resolution of 156.25 Hz (Low band) or 312.5 Hz (High band). The transmit data rate can be programm ed between 0.123–256 kbps, an d the frequency deviation can be programmed between ±1–320 kHz. These parameters may be adjusted via registers as shown in "3.5. Frequency Control". Figure 16. PLL Synthesizer Block Diagram The reference frequenc y to the PLL is 10 MHz. The PLL utilizes a differential L-C VCO, with integrated on-chip inductors. The output of the VCO is fo llowed by a configurable divider whic h will divide down the signal to the desired output frequency band. The modu lus of the variable divide-by-N divi der stage is controlled dynamically by N LP FCPPF D Delt Sigma F ref = 10 M VCO TX Modulation Sele ctable Divider TX RX Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com choosing data rate, deviation, channel
output from the - modulator. The tuning resolution is sufficient to tune to the commanded frequency with a maximum accuracy of 312.5 Hz anywhere in the range between 240–960 MHz. 5.6.1. VCO The output of the VCO is automatically divided down to the correct output frequency depending on the hbsel and fb[4:0] fields in "Register 75h. Frequency Band Select." In receive mode, the LO frequency is automatically shifted downwards by the IF frequency of 937.5 kHz, allowing transmit and receive operation on the same frequency. The VCO integrates the resonator inductor and tuning varactor, so no external VCO components are required. The VCO uses a capacitance bank to cover the wide frequency range sp ecified. The capacitance bank will automatically be calibrated every time the synthesizer is enabled. In certain fast hopping applications this might not be desirable so the VCO calibration may be skipped by setting the appropriate register. 5.7. P ower Amplifier Th e RFM22B contains an internal integrated power amplifier (PA) capable of transmitting at output levels between –1 and +20 dBm. The RFM23B contains a PA which is capable of transmitting output levels between –8 to +13 dBm. The PA design is single-ended and is implemented as a two stage class CE amplifier with a high efficiency when transmitting at maximum power. The PA efficiency can only be optimized at one power level. Changing the output power by adjusting txpow[2:0] will scale both the ou tput power and current but the efficiency will not remain constant. The PA output is ramped up and down to prevent unwanted spectral splatter. For the RFM23B, The direct tie is used, The lna_sw bit in “Register 6Dh. TX Power” must be set. 5.7.1. Output Power Selection The output power is configurable in 3 dB steps with the txpow[2:0] field in "Register 6Dh. TX Power." Extra output power can allow the use of a cheaper smaller antenna, greatly reducing the overall BOM cost. The higher power setting of the chip achieves maximum possible range, but of course comes at the co st of higher TX current consumption. However, depending on the duty cycle of the system, the effect on battery life may be insignificant. Contact HOPERF Support for help in evaluating this tradeoff. Add R/W Function/D escription D6 D5 D4 D3 D2 D1 D0 POR Def. 6D R/W TX Power papeakval papeaken papeaklv[1] papeaklv[0] lna_sw txpow[2] txpow[1] txpow[0] 18h t xpow[2:0] RFM22B Output Power 000 +1 dBm 001 +2 dBm 010 +5 dBm 011 +8 dBm 100 +11 dBm 101 +14 dBm 110 +17 dBm 111 +20 dBm txpow[2:0] RFM23B Output Power 000 –8 dBm 001 –5 dBm 010 –2 dBm 011 +1 dBm 100 +4 dBm 101 +7 dBm 110 +10 dBm 111 +13 dBm Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
5.8. Cryst al Oscillator The RFM22B/23B in cludes an integrated 30 MHz crystal oscillator with a fast start-up time of less than 600 s. A parallel resonant 30MHz crystal is used on the module. Th e design is differential with the required capacitance integrated on-chip to minimize the number of external components. The crystal load capacitance can be digitally programme d to accommodate crystals with various load capacitance requirements and to adjust the frequency of the crystal oscillator. The tuning of t he crystal load capacitance is programmed through the xlc[6: 0] field of "Register 09h. 30 MHz Crysta l Oscillator Load Capacitance." The total internal capacitance is 12.5 pF and is adjustable in approximately 127 steps (97fF/step). The xtalshift bit provides a coarse shift in frequency but is not binary with xlc[6:0]. The crystal frequency adjustment can be used to compensate for crystal production tolerances. Utilizing the on- chip temperature sensor and suitable control softwa re, the temperature depende ncy of the crystal can be canceled. The typical value of the total on-chip capacitance Cint can be calculated as follows: Cint = 1.8 pF + 0.085 pF x xlc[6:0] + 3.7 pF x xtalshift Note that the coarse shift bit xtalshift is not binary with xlc[6:0]. The total load capacitance Cload seen by the crystal can be calculated by adding the sum of all external parasitic PCB capacitances Cext to Cint. If the maximum value of Cint (16.3 pF) is not sufficient, an external capacito r can be added for exact tuning. If AFC is disabled then the synthesizer frequency may be further adjusted by programming the Frequency Offset field fo[9:0]in "Register 73h. Frequen cy Offset 1" and "Register 74h. Frequen cy Offset 2", as discussed in "3.5. Frequency Control" . The crystal oscillator frequency is divided down internally and may be output to the microcontroller through one of the GPIO pins for use as the System Clock. In this fashion, only one crysta l oscillator is required for the entire system and the BOM cost is reduced. The available clo ck frequencies and GPIO configuration are discussed further in "8.2. Microcontroller Clock" . 5.9. Regulato rs T here are a total of six regulators integrated onto the RF M22B/23B . With the exception of the digital regulator, all regulators are designed to operate with only internal de coupling. input supply voltage from +1.8 to +3.6V. A supply voltage should only be connected to the VDD pins. Add R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def.
09 R/W Crystal Oscillator Load
xtalshift xlc[6] xlc[5] xlc[4] xlc[3] xlc[2] xlc[1] xlc[0] 7Fh Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com cr ystal load All regulators are designed to operate with an
- Dat a Handling and Packet Handler Th e internal modem is designed to operate with a packet including a 10101... preamble structure. To configure the modem to operate with packet formats without a preamble or other legacy packet st ructures contact customer support. 6.1. RX and TX FIFOs T wo 64 byte FIFOs are integrated into the chip, one for RX and one for TX, as shown in Figure 17. "Register 7Fh. FIFO Access" is used to access both FIFOs. A burst write, as described in "3.1. Serial Peripheral Interface (SPI)" to address 7Fh will write da ta to the TX FIFO. A bur st read from address 7Fh will read data from the RX FIFO. Figure 17. FIFO Thresholds Th e TX FIFO has two programmable thresholds. An interrup t event occurs when the data in the TX FIFO reaches these thresholds. The first threshold is the FIFO almost full threshold, txaf thr[5:0]. The value in this register corresponds to the desired threshold value in number of bytes. When the data being filled into the TX FIFO crosses this threshold limit, an interrupt to the microcontroller is generated so the chip can enter TX mode to transmit the contents of the TX FIFO. The second threshold for TX is the FIFO almost empty threshold, txaethr[5:0]. When the data being shifted out of the TX FIFO drops below the almost empty threshol d an interrupt will be generated. The microcontroller will need to s witch out of TX mode or fill more data into the TX FIFO. Th e transceiver can be configured so that when the TX FIFO is empty it will automatically exit th e TX state and return to one of the low power states. When TX is initiated, it will transmit the nu mber of bytes programmed into the packet length field (Reg 3Eh). When the packet ends, the chip will return to the state s pecified in register 07h. For example, if 08h is written to address 07h then the chip will return to the STANDBY state. If 09h is written then t he chip will return to the READY state. TX FIFO RX FIFO R X FIFO Almost Full Threshold TX F IFO Almost Empty Threshold TX FI FO Almost Full Threshold Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
e RX FIFO has one programmable threshold called the FIFO Almost Full Threshold, rxafthr[5:0]. When the incoming RX data crosses the Almost Full Threshold an interrupt will be gene rated to the microcontroller via the nIRQ pin. The microcontroller will then need to read the data from the RX FIFO. Both the TX and RX FIFOs may be cleared or reset with the ffclrtx and ffclrrx bits. All interrupts may be enabled by setting the Interrupt Enabled bits in "Register 05h. Interrupt Enable 1" and “Register 06h. Interrupt Enable 2.” If the interrupts are not enab led the function will not generate an interrupt on the nIRQ pi n but the bits will still be read correctly in the Interrupt Status registers. 6.2. Packet Configuratio n Whe n using the FIFOs, automatic packet handling may be enabled for TX mode, RX mode, or both. "Register 30h. Data Access Control" through “Register 4Bh. Received Packet Length” control the configuration, status, and decoded RX packet data for Packet Handling. The usual fields for network communication (such as preamble, synchronization word, headers, packet length, and CRC) ca n be configured to be automatically added to the data payload. The fields needed for packet generation norma lly change infrequently and can therefore be stored in registers. Automatically adding these fields to the data payload greatly reduces the amount of communication between the microcontroller and the RFM22B/23B and reduces the required computational power of the microcontroller. The general packet structure is shown in Figure 18. The length of each field is shown below the field. The preamble pattern is always a series of alternating ones and zero es, starting with a zero. All the fields have programmable lengths to accommodate different applications. The most common CRC polynominals are available for selection. Figure 18. Packet Structure An o verview of the packet handler configuration registers is shown in Table 13. Add R/W Function/D escription D Def.
08 R/W Operating &
antdiv[2] antdiv[1] antdiv[0] rxmpk autotx enldm ffclrrx ffclrtx 00h 7C R/W TX FIFO Control 1 Reserved Reserved txafthr[5] txafthr[4] txaf thr[3] txafthr[2] txafthr[1] txafthr[0] 37h 7D R/W TX FIFO Control 2 Reserved Reserved txaethr[5] txaethr[4] txaethr[3] txaethr[2] txaethr[1] txaethr[0] 04h Add R/W Function/De scription D6 D5 D4 D3 D2 D1 D0 POR Def. 7E R/W RX FIFO Control Reserved Reserved rxafthr[5] rxafthr[4] rxaf thr[3] rxafthr[2] rxafthr[1] rxafthr[0] 37h Da taPreamble Sy nc Word TX Header Packet Length CRC
512 B ytes 1-
4 Bytes
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6.3. Packet Handler TX Mode If the TX packet length is set the pa cket handler will send the number of by tes in the packet le ngth field before returning to IDLE mode and asserting the packet sent interrupt. To resume sending data from the FIFO the microcontroller needs to command the chip to re-enter TX mode. Figure 19 provides an example transaction where the packet length is set to three bytes. Figu re 19. Multiple Packets in TX Packet Handler 6.4. Packet Handler RX Mode 4.1. Packet Handler Disabled When the packet handler is disabled certain fields in the received packet are still required. Proper modem operation requires preamble and sync when the FIFO is being used, as shown in Fi gure 20. Bits after sync will be treated as raw data with no qualification. This mode allo ws for the creation of a custom packet handler when the automatic qualification parameters are not sufficient. Manchester encoding is supported but data whitening, CRC, and header checks are not. Figure 20. Required RX Packet Structure with Packet Handler Disabled 4.2. Packet Handler Enabled When the packet handler is enabled, all the fields of t he packet structure need to be configured. Register contents are used to construct the header field and length information encoded into the transmitted packet when transmitting. The receive FIFO can be configured to handle packets of fixed or variab le length with or without a header. If multiple packets are desired to be stored in th e FIFO, then there are options available for the different fields that will be stored into the FIFO. Figure 21 demonstrates the option s and settings available when multiple packets are enabled. Figure 22 demonstrates the operation of fixed packet length and correct/incorrect packets. Fi gure 21. Multiple Packets in RX Packet Handler Da ta 1 Data 2 Data 3 Data 4 Data 5 Data 6 Data 7 Data 8 Data 9 T his will be sent in the first transmission This will be sent in the second transmission This will be sent in the third transmission Pr eamble SYNC DATA Regi ster Data Reg ister Data FI FO Data Heade r(s) Len gth r x_multi_pk_en = 1 H Da ta rx_multi_pk_en = 0 txhdlen = 0 txhdlen > 0 fixpklenfixpklen 0 101 Da ta Da taDa ta Da ta L L H R X FIFO Contents:Transmission: Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- Multiple Packets in RX with CRC or Header Error Da ta L H Da ta L H Da ta L H Da ta L H Wr ite Pointer Wr ite Pointer RX FIFO Addr. R X FIFO Addr. Da ta L H Wr ite Pointer RX FIFO Addr. Da ta L H Da ta L H Wr ite Pointer RX FIFO Addr. CR C error Da ta L H Da ta L H Wr ite Pointer RX FIFO Addr. In itial state PK 1 OK PK
2 OK PK
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T able 13. Packet Handler Registers Ad d R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def. R/W Data Access Control e npacrx lsbfrst crcdonly skip2ph enpactx encrc crc[1] crc[0] 8Dh
31 R EzMAC status 0 rxcrc1 pksrch pkrx pkvalid crcerror pktx pksent —
32 R/W Header Control 1 bcen[3:0] hdch[3:0] 0Ch
33 R/W Header Control 2 skipsyn hdlen[2] hdlen[1] hdl en[0] fixpklen synclen[1] synclen[0] prealen[8] 22h 34 R/W Preamble Length prealen[7] prealen[6] prealen[5] prealen[4] prealen[3] prealen[2] prealen[1] prealen[0] 08h 35 R/W Preamble Detection Control preath[4] preath[3] preath[2] preath[1] preath[0] rssi_off[2] rssi_off[1] rssi_off[0] 2Ah
36 R/W Sync Word 3 sync[31] sync[30] sync[29] sync[28] sync[27] sync[26] sync[25] sync[24] 2Dh
37 R/W Sync Word 2 sync[23] sync[22] sync[21] sync[20] sync[19] sync[18] sync[17] sync[16] D4h
38 R/W Sync Word 1 sync[15] sync[14] sync[13] sync[12] sync[11] sync[10] sync[9] sync[8] 00h
39 R/W Sync Word 0 sync[7] sync[6] sync[5] s ync[4] sync[3] sync[2] sync[1] sync[0] 00h
3A R/W Transmit Header 3 txhd[31] txhd[30] txhd[29] txhd[28] txhd[27] txhd[26] txhd[25] txhd[24] 00h 3B R/W Transmit Header 2 txhd[23] txhd[22] txhd[21] txhd[20] txhd[19] txhd[18] txhd[17] txhd[16] 00h 3C R/W Transmit Header 1 txhd[15] txhd[14] txhd[13] txhd[12] txhd[11] txhd[10] txhd[9] txhd[8] 00h 3D R/W Transmit Header 0 txhd[7] txhd[6] txhd[ 5] txhd[4] txhd[3] txhd[2] txhd[1] txhd[0] 00h 3E R/W Transmit Packet Length pklen[7] pklen[6] pklen[ 5] pklen[4] pklen[3] pklen[2] pklen[1] pklen[0] 00h 3F R/W Check Header 3 chhd[31] chhd[30] chhd[29] chhd[28] chhd[27] chhd[26] chhd[25] chhd[24] 00h
40 R/W Check Header 2 chhd[23] chhd[22] chhd[21] chhd[20] chhd[19] chhd[18] chhd[17] chhd[16] 00h
41 R/W Check Header 1 chhd[15] chhd[14] chhd[13] chhd[12] chhd[11] chhd[10] chhd[9] chhd[8] 00h
42 R/W Check Header 0 chhd[7] chhd[6] chhd[5] chhd[4] chhd[3] chhd[2] chhd[1] chhd[0] 00h
43 R/W Header Enable 3 hden[31] hden[30] hden[29] hden[28] hden[27] hden[26] hden[25] hden[24] FFh
44 R/W Header Enable 2 hden[23] hden[22] hden[21] hden[20] hden[19] hden[18] hden[17] hden[16] FFh
45 R/W Header Enable 1 hden[15] hden[14] hden[13] hden[12] hden[11] hden[10] hden[9] hden[8] FFh
46 R/W Header Enable 0 hden[7] hden[6] hden[5] hden[4] hden[3] hden[2] hden[1] hden[0] FFh
47 R Received Header 3 rxhd[31] rxhd[30] rxhd[ 29] rxhd[28] rxhd[27] rxhd[26] rxhd[25] rxhd[24] —
48 R Received Header 2 rxhd[23] rxhd[22] rxhd[ 21] rxhd[20] rxhd[19] rxhd[18] rxhd[17] rxhd[16] —
49 R Received Header 1 rxhd[15] rxhd[14] rxhd[ 13] rxhd[12] rxhd[11] rxhd[10] rxhd[9] rxhd[8] —
4A R Received Header 0 rxhd[7] rxhd[6] rxhd[5 ] rxhd[4] rxhd[3] rxhd[2] rxhd[1] rxhd[0] — 4B R Received Packet Length rxplen[7 ] rxplen[6] rxplen[5] rxplen[4] rxplen[3] rxplen[2] rxplen[1] rxplen[0] — Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
6.7. Preamble Length Th e preamble detection threshold determines the number of valid preamble bits the radio must receive to qualify a valid preamble. The preamble threshold should be adjusted depending on the nature of the application. The required preamble length th reshold will depend on when receive mode is entered in relation to the start of the transmitted packet and the length of the transmit prea mble. With a shorter than recommended preamble detection threshold the probability of false detection is directly related to how long the receiver operates on noise before the transmit preamble is received. False detection on noise may cause the actual packet to be missed. The preamble detection threshold is programmed in register 35h. For most applications with a preamble length longer than 32 bits the default value of 20 is recommended for the preamble detection threshold. A shorter Preamble Detection Threshold may be chosen if occasional false detections may be tolerated. When antenna diversity is enabled a 20- bit preamble detection threshold is recommended. When th e receiver is synchronously enabled just before the start of the packet, a shorter preamble detection threshold may be used. Table 14 demonstrates the recommended preamble detection threshold and preamble length for various modes. It is possible to use RFM22B/23B in a raw mode without the requirement for a 101010 preamble. Contact customer support for further details. Note : The recommended preamble length and preamble detection threshold listed above are to achieve 0% PER. They may be shortened when occasional packet errors are tolerable. 6.8. Invalid Preamble Detector When scanning channels in a f requency hopping system it is desirable to deter mine if a channel is valid in the minimum amount of time. The preamble detector can output an invalid preamble detect signal. which can be used to identify the channel as invalid. After a configurable ti me set in Register 60h[7:4], an invalid preamble detect signal is asserted indicating an invalid channel. The perio d for evaluating the signal for invalid preamble is defined as (inv_pre_th[3:0] x 4) x Bit Rate Period. The preamble detect and invalid preamble detect signals are available in "Register 03h. Interrupt/Status 1" and “Register 04h. Interrupt/Status 2.” 6.9. Synchronization W ord Configuration Th e synchronization word length for both TX and RX can be configured in Reg 33h, synclen[1:0]. The expected or transmitted sync word can be configured from 1 to 4 bytes as defined below: synclen[1 :0] = 00—Expected/Transmitted Synchronization Word (sync word) 3. synclen[1 :0] = 01—Expected/Transmitted Synchroniz ation Word 3 first, followed by sync word 2. synclen[1 :0] = 10—Expected/Transmitted Synchronization Word 3 first, followed by sync word 2, followed by sync word 1. synclen[1 :0] = 1—Send/Expect Synchroniz ation Word 3 first, followed by sync word 2, followed by sync word 1, followed by sync word 0. The sync is transmitted or expected in the following sequence: sync 3 sync 2sync 1sync 0. The sync word values can be programmed in Registers 36h–39h. After preamble detection, the part will search for sync for a fixed T able 14. Minimum Receiver Settling Time M ode Approximate Receiver Settling Time Recommended Preamble Length with 8-Bit Detection Threshold Recommended Preamble Length with 20-Bit Detection Threshold (G)F SK AFC Disabled 1 byte 20 bits 32 bits (G)FSK AFC Enabled 2 byte 28 bits 40 bits (G)FSK AFC Disabled +Antenna Diversity Enabled 1 byte — 64 bits (G)FSK AFC Enabled +Antenna Diversity Enabled 2 byte — 8 byte OOK 2 byte 3 byte 4 byte OOK + Antenna Diversity Enabled 8 byte — 8 byte Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
period of time. If a sy nc is not recognized in this period, a timeout will occur, and the search for preamble will be re- initiated. The timeout period after preamble detections is defined as the value programmed into the sync word length plus four additional bits. 6.10. Receive Header Check Th e header check is designed to support 1–4 bytes and broadcast headers. The header length needs to be set in register 33h, hdlen[2:0]. The headers to be checked need to be set in register 32h, hdch[3:0]. For instance, there can be four bytes of header in the packet structure but on ly one byte of the header is set to be checked (i.e., header 3). For the headers that are set to be checked, the expected value of the header should be programmed in chhd[31:0] in Registers 3F–42. The individual bits within the selected bytes to be checked can be enabled or disabled with the header enables, hden[31:0] in Registers 43–46. For example, if you want to check all bits in header 3 then hden[31:24] should be set to FF but if only the last 4 bits are desired to be checked then it should be set to 00001111 (0F). Broadcast headers can also be programmed by setting bcen[3:0] in Register 32h. For broadcast header check the value may be either “FFh” or the value stored in the Check Header register. A logic equivalent of the header check for Header 3 is shown in Figure 25. A similar logic check will be done for Header 2, Header 1, and Header 0 if enabled. F igure 25. Header 6.1 1. TX Retransmission and Auto TX Th e RFM22B/23B is capable of automatically retransmit ting the last packet loaded in the TX FIFO. Automatic retransmission is set by entering the TX state with the txon bit without reloading the TX FIFO. This feature is useful for beacon transmission or when retransmission is requ ired due to the absence of a valid acknowledgement. Only packets that fit completely in the TX FIFO can be automatically retransmitted. An automatic transmission function is available, allowing the radio to automatically start or stop a transmission depending on the amount of data in the TX FIFO. When autotx is set in “Register 08. Operating & Function Control 2", the transceiver will automatically enter the TX state when the TX FIFO almost full threshold is exceed ed. Packets will be transmitted according to the configured packet length. To stop transmitting, clear the packet sent or TX FIFO almost empty interrupts must be cleared by reading register. BI T WISE rxhd[31:24] BI T WISE chhd[31:24] hden[31:24] = FF h hd ch[3] he ader3_ok E xample for Header 3 E quivalence comparison rx hd[31:24] E quivalence comparison bc en[3] Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- RX Modem Configuration A M icrosoft Excel (WDS) parameter calculator or Wirele ss Development Suite (WDS) calculator is provided to determine the proper settings for the modem. The calculator can be found on www.hoperf.com or on the CD provided with the demo kits. An application note is available to describe how to use the calculator and to provide advanced descriptions of the modem settings and calculations. 7.1. Modem Settings for FSK and GFSK Th e modem performs channel selection and demodulation in the digital domain. The channel filter bandwidth is configurable from 2.6 to 620 kHz. The receiver data-rate, modulation index, and bandwidth are set via registers 1C–25h. The modulation index is equal to 2 times the peak deviation divided by the data rate (Rb). When Manchester coding is disabled, the required channel filter bandwidth is calculated as BW = 2Fd + Rb where Fd is the frequency deviation and Rb is the data rate. Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- Auxiliary Functions 8.1. Smart Reset Th e RFM22B/23B contains an enhanced integrated SMART RESET or POR ci rcuit. The POR circuit contains both a classic level threshold reset as well as a slope detector POR. This reset circuit was designed to produce a reliable reset signal under any circumstances. Reset will be initiated if any of the following conditions occur: Initial power on, VDD starts from gnd: reset is active till VDD reaches VRR (see table); Whe n VDD decreases below VLD for any reason: reset is active till VDD reaches VRR; A so ftware reset via “Register 08h. Operating Mode and Function Control 2”: reset is active for time TSWRST On th e rising edge of a VDD glitch when the supply voltage exceeds the following time functioned limit: F igure 26. POR Glitch Parameters The res et will initialize all registers to their default values. The reset signal is also av ailable for output and use by the microcontroller by using the default setting for GPIO_0 . The inverted reset signal is available by default on GPIO_1. T able 15. POR Parameters Para meter Symbol Comment Min Typ Max Unit Release Reset Voltage VRR 0.85 1.3 1.75 V Power-On VDD Slope SVDD tested VDD slope region 0.03 300 V/ms Low VDD Limit VLD VLD<VRR is guaranteed 0.7 1 1.3 V Software Reset Pulse TSWRST 50 470 us Threshold Voltage VTSD 0.4 V Reference Slope k 0.2 V/ms VDD Glitch Reset Pulse TP Also occurs after SDN, and initial power on 51 6 4 0 m s Re set TP t=0 VDD starts to rise t VDD(t) rese Vglitch>=0.4+t*0.2V/ms actu al VDD(t) showing glitch reset li mit: 0.4V+t*0.2V/ms VDD nom. 0.4V Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
8.2. Microcontroller Clock The 30 MHz crystal oscillator frequency is divided down internally and may be output to the microcontroller through GPIO2. This feature is useful to lower BOM cost by using only one crystal in the system. The system clock frequency is selectable from one of 8 options, as shown below. Except for the 32.768 kHz option, all other frequencies are derived by dividing the crystal oscillator frequency. The 32.768 kHz clock signal is derived from an internal RC oscillator or an external 32 kHz crystal. The default setting for GPIO2 is to output the microcontroller clock signal with a frequency of 1 MHz. If the microcontroller clock option is being used there ma y be the need of a system clock for the microcontroller while the RFM22B/23B is in SLEEP mode. Since the crystal oscillator is disabled in SLEEP mode in order to save current, the low-power 32.768 kHz clock can be automatically switched to become the microcontroller clock. This feature is called enable low frequency clock and is enabled by the enlfc bit in “Register 0Ah. Microcontroller Output Clock." When enlfc = 1 and the chip is in SLEEP mode then the 32.768 k Hz clock will be provided to the microcontroller as the system clock, regardless of the setting of mclk[2:0]. For example, if mclk[2:0] = 000, 30 MHz will be provided through the GPIO output pin to the micr ocontroller as the system cl ock in all IDLE, TX, or RX states. When the chip enters SLEEP mode, the system clock will automatically switch to 32.768 kHz from the RC oscillator or 32.768 XTAL. Another available feature for the microcontroller clock is the clock tail, clkt[1:0] in “Register 0Ah. Microcontroller Output Clock." If the low frequency clock feature is not enabled (enlfc = 0), then the system clock to the microcontroller is disabled in SLEEP mode. However, it may be usef ul to provide a few extra cycles for the microcontroller to complete its operation prior to the shutdo wn of the system clock signal. Setting the clkt[1:0] field will provide additional cycles of the system clock before it shuts off. If an interrupt is triggered, the microcontroller clock will remain enabled regardless of the selected mode. As soon as the interrupt is read the state machine will then move to the selected mode. The minimum current consumption will not be achieved until the interrup t is read. For instance, if the ch ip is commanded to SLEEP mode but an interrupt has occurred the 30 MHz XTAL will not be disabled until the interrupt has been cleared. Add R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def. 0A R/W Microcontroller Output Clock clkt[1] clkt[0] enlfc mclk[2] mclk[1] mclk[0] 06h mclk[2:0] Clock Frequency 0 30 MHz 001 15 MHz 010 10 MHz 011 4 MHz 100 3 MHz 101 2 MHz 110 1 MHz 111 32.768 kHz clkt [1:0] Clock Tail 00 0 cycles 01 12 8 cycles 10 256 cycles 11 512 cycles Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
8.3. General Purpose ADC An 8- bit SAR ADC is integrated for general purpose use, as well as for digitizing the on-chip temperature sensor reading. Registers 0Fh "ADC Confi guration", 10h "Sensor Offset" and 4Fh "Amplifier Offset" can be used to configure the ADC operation. Every time an ADC conversion is desired, bit 7 "adcstar t/adcbusy" in Register 1Fh “Clock Recovery Gearshift Override” must be set to 1. This is a self clearing bit that will be reset to 0 at the end of the conversion cycle of the ADC. The conversion time for the ADC is 350 µs. After this time or when the "adcstart/adcbusy" bit is cleared, then the ADC value may be read out of “Register 11h. ADC Value." The architecture of the ADC is shown in Figure 27. The signal and reference inputs of the ADC are selected by adcsel[2:0] and adcref[1:0] in register 0Fh “ADC Configuration”, respectively. The default setting is to read out the temperature sensor using the bandgap voltage (VBG) as reference. With the VBG reference the input range of the ADC is from 0-1.02 V with an LSB resolution of 4 mV (1.02/255). Changing the ADC reference will change the LSB resolution accordingly. A differential multiplexer and amplifier are provided for interfacing external bridge sensors. The gain of the amplifier is selectable by adcgain[1:0] in Register 0Fh. The majority of sensor bridges have supply voltage (VDD) dependent gain and offset. The reference voltage of the ADC can be changed to either V DD/2 or VDD/3. A p rogrammable VDD depe ndent offset voltage can be added using soffs[3:0] in register 10h. Figure 27. General Purpose ADC Architecture Add R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def. 0F R/ W ADC Configuration adcstart/adcbusy adcsel[2] adcsel[1] adcsel[0] adcref[1] adcref[0] adcgain[1] adcgain[0] 00h
10 R/W Sensor Offset soffs[3] soffs[2] soffs[1] soffs[0] 00h
11 R ADC Value adc[7] adc[6] adc[5] adc[4] adc[3] adc[2] adc[1] adc[0] —
…… …… Di ff. MUX Diff. Amp. Input MUX Ref MUX Vin Vref adcs el [2:0] aoffs [4:0] adcgain [1:0] adcsel [2:0] adcref [1:0] adc [7:0] VDD / 3 VDD / 2 GPI GPIO0 GPIO2 Temperature Sensor VBG (1. 2V) 8-bit ADC 0 -1020mV / 0-255 soffs [3:0] Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
8.4. T emperature Sensor An integrated on-chip analog temperature sensor is av ailable. The temperature sensor will be automatically enabled when the temperature sensor is selected as the input of the ADC or when the analog temp voltage is selected on the analog test bus. The temperature sens or value may be digitized using the general-purpose ADC and read out over the SPI through "Register 10h. ADC S ensor Amplifier Offset." T he range of the temperature sensor is configurable. Table 16 lists the settings for the different temperature ranges and performance. To use the Temp Sensor: 1. Set the input for ADC to the temperature sensor, "Register 0Fh. ADC Configuration"—adcsel[2:0] = 000 2. Set the reference for ADC, "Register 0Fh. ADC Configuration"—adcref[1:0] = 00 3. Set the temperature range for ADC, "Register 12h. Temperature Sensor Calibration"—tsrange[1:0] 4. Set entsoffs = 1, "Register 12h. Temperature Sensor Calibration" 5. Trigger ADC reading, "Register 0Fh. ADC Configuration"—adcstart = 1 6. Read temperature value—Read contents of "Register 11h. ADC Value" The slope of the temperature sensor is very linear and monotonic. For absolute accuracy better than 10 °C calibration is necessary. The temperature sensor may be calibrated by setting entsoffs = 1 in “Register 12h. Temperature Sensor Control” and settin g the offset with the tvoffs[7:0] bits in “Register 13h. Temperature Value Offset.” This method adds a positive offset digitally to the ADC value that is read in “Register 11h. ADC Value.” The other method of calibration is to us e the tstrim which compensates the anal og circuit. This is done by setting entstrim = 1 and using the tstrim[2:0] bits to offset the temperature in “Register 12h. Temperature Sensor Control.” With this method of calibration, a negative offset may be achieved. With both methods of calibration better than ±3 °C absolute accuracy may be achieved. The different ranges for the temperature sensor and ADC8 are demonstrated in Figure 28. The value of the ADC8 may be translated to a temperature reading by ADC8 Value x ADC8 LSB + Lowest Temperature in Temp Range. For instance for a tsrange = 00, Temp = ADC8Value x 0.5 – 64. Ad d R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def.
12 R/W Temperature
t srange[1] tsrange[0] entsoffs entstrim tstrim[3] tstrim[2] vbgtrim[1] vbgtrim[0] 20 h
13 R/W Temperature Value Offset tvo
ffs[7] tvoffs[6] tvoffs[5] tvoffs[4] tvoffs[3] tvoffs[2] tvoffs[1] tvoffs[0] 00 h T able 16. Temperature Sensor Range entoff tsrange[1] tsrange[0] Temp. range Unit Slope ADC8 LSB 1 0 0 1 0 1 –64 … 192 °C 4 mV/°C 1 °C 1 1 0 0 … 128 °C 8 mV/°C 0.5 °C 1 1 1 –40 … 216 °F 4 mV/°F 1 °F 0* 1 0 0 … 341 °K 3 mV/°K 1.333 °K *Note: Absolute temperature mode, no temperature shift. This mode is only for test purposes. POR value of EN_TOFF is 1. Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
e 28. Temperature Ranges using ADC8 Te mperature Measurement with ADC8 150 200 250 300 -40 -20 0 20 40 60 80 100 T emperature [Celsius] S ensor Range 0 S ensor Range 1 S ensor Range 2 S ensor Range 3 AD C Val ue Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
8.5. Lo w Battery Detector A low ba ttery detector (LBD) with digital read-out is integrated into the chip. A digital threshold may be programmed into the lbdt[4:0] field in "Registe r 1Ah. Low Battery Detector Threshol d." When the digitized battery voltage reaches this threshold an interrupt will be generated on the nIRQ pin to the microcontroller. The microcontroller can confirm source of the interrupt by reading "Register 03h. Interrupt/Status 1" and “Register 04h. Interrupt/Status 2.” If the LBD is enabled while the chip is in SLEEP mode, it will automatically enable th e RC oscillator which will periodically turn on the LBD circuit to measure the battery voltage. The battery voltage may also be read out through "Register 1Bh. Battery Voltage Level" at any time when the LBD is enabled. The low battery detect function is enabled by setting enlbd=1 in "Register 07h. Operating Mode and Function Control 1". The LBD output is digitized by a 5-bit ADC. When t he LBD function is enabled (enlbd = 1 in "Register 07h. Operating Mode and Function Control 1") the battery vo ltage may be read at anytime by reading "Register 1Bh. Battery Voltage Level." A battery voltage threshold may be programmed in “Register 1Ah. Low Battery Detector Threshold." When the battery voltage level drops below the battery voltage threshold an interrupt will be generated on the nIRQ pin to the microcontroller if the LBD interrupt is enabled in “Register 06h. Interrupt Enable 2.” The microcontroller will then need to verify the interrupt by reading the interr upt status register, addresses 03 and 04h. The LSB step size for the LBD ADC is 50 mV, with the ADC range demonstrated in the table below. If the LBD is enabled the LBD and ADC will automatically be enabled every 1 s for approximately 250 µs to measure the voltage which minimizes the current consumption in Sensor mode. Before an interrupt is activated four consecutive readings are required. Ad R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def. 1A R/W Low Battery Detector Threshold lbdt[4] lbdt[3] lbdt[2] lbdt[1] lbdt[0] 14h 1B R Battery Voltage Level 0 0 0 vbat[4] vbat[3] vbat[2] vbat[1] vbat[0] — AD C Value VDD Voltage [V] 0< 1.7 1 1 .7–1.75 2 1.75–1.8 29 3.1–3.15 30 3.15–3.2 31 > 3.2 ADCValuemVtageBatteryVol 50 7 . 1 Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
8.6. W ake-Up Timer and 32 kHz Clock Source The chip cont ains an integrated wake-up timer which can be used to periodically wake the chip from SLEEP mode. The wake-up timer runs from the internal 32.768 kHz RC Oscillator. The wake-up timer can be configured to run when in SLEEP mode. If enwt = 1 in "Register 07h. Operating Mode and Function Control 1" when entering SLEEP mode, the wake-up timer will c ount for a time specified defined in Registers 14–16h, "Wake Up Timer Period." At the expiration of this period an interr upt will be generated on the nIRQ pin if this interrupt is enabled. The microcontroller will then need to verify the interrupt by reading the Registers 03h–04h, "Interrupt Status 1 & 2". The wake-up timer value may be read at any time by the wtv[15:0] read only registers 17h–18h. The formula for calculating the Wake-Up Period is the following: Use of the D variable in the formula is only necessary if fi ner resolution is required than can be achieved by using the R value. There are two different methods for utilizing the wake-up timer (WUT) depending on if the WUT interrupt is enabled in “Register 06h. Interrupt Enable 2.” If the WUT inte rrupt is enabled then nIRQ pin will go low when the timer expires. The chip will also change state so that the 30 MH z XTAL is enabled so that the microcontroller clock output is available for the microcontroller to use to process the interrupt. The other method of use is to not enable the WUT interrupt and us e the WUT GPIO setting. In this mode of operation the chip will not change state until commanded by the microcontroller. The different mode s of operating the WUT and the current consumption impacts are demonstrated in Figure 29. A 32 kHz XTAL may also be used for better timing accuracy. By setting the x32 ksel bit in Register 07h "Operating & Function Control 1", GPIO0 is automatically reconfigured so that an external 32 kHz XTAL may be connected to this pin. In this mode, the GPIO0 is extremely sensitiv e to parasitic capacitance, so only the XTAL should be connected to this pin with the XTAL physically located as close to the pin as possible. Once the x32 ksel bit is set, all internal functions such as WUT, micro-controller clock, and LDC mode will use the 32 kHz XTAL and not the 32 kHz RC oscillator. WUT Re gister Description wtr[4:0] R Value in Formula wtm[15:0] M Value in Formula Add R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def.
14 R/W Wake-Up Timer Period 1 wtr[4] wtr[3] wtr[2] wtr[1] wtr[0] 03h
15 R/W Wake-Up Timer Period 2 wtm[15] wtm[14] w tm[13] wtm[12] wtm[11] wtm[10] wtm[9] wtm[8] 00h
16 R/W Wake-Up Timer Period 3 wtm[7] wtm[6 ] wtm[5] wtm[4] wtm[3] wtm[2] wtm[1] wtm[0] 00h
17 R Wake-Up Timer Value 1 wtv[15] wtv[14] w tv[13] wtv[12] wtv[11] w tv[10] wtv[9] wtv[8] —
18 R Wake-Up Timer Value 2 wtv[7] wtv[6] w tv[5] wtv[4] wtv[3] wtv[2] wtv[1] wtv[0] —
R 768 . 32 4 Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- WUT Interrupt and WUT Operation W UT Period GPIOX =00001 nIRQ SPI Interrupt Read Chip State Current Consumption Sleep Ready Sleep Ready Sleep Ready Sleep 1 uA 1.5 mA 1.5 mA W UT Period GPIOX =00001 nIRQ SPI Interrupt Read Chip State Current Consumption Sleep 1 uA I nterrupt Enable enwut =1 ( Reg 06h) Interrupt Enable enwut =0 ( Reg 06h) 1 uA 5 mA 1 uA Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
8.7. Lo w Duty Cycle Mode The Low Duty Cycle Mode is available to automatically wake-up the receiver to check if a valid signal is available. The basic operation of the low duty cycle mode is demonstrated in the figure below. If a valid preamble or sync word is not detected the chip will return to sleep mode until the beginning of a new WUT period. If a valid preamble and sync are detected the receiver on period will be extended for the low duty cycl e mode duration (TLDC) to receive all of the packet. The WUT period must be set in conjunction with the low duty cycle mode duration. The R value (“Register 14h. Wake-up Timer Period 1”) is shared between the WUT and the TLDC. The ldc[7:0] bits are located in “Register 19h. Low Duty Cycle Mode Duration .” The time of the TLDC is determined by the formula below: Fig ure 30. Low Duty Cycle Mode msldcTLDC R 768 . 32 4] 0 : 7 [ Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
8.8. GPIO Configurat ion Th ree general purpose IOs (GPIOs) are available. Numerous functions such as specific interrupts, TRSW control, Microcontroller Output, etc. can be routed to the GPIO pins as shown in the tables below. When in Shutdown mode all the GPIO pads are pulled low. Note : The ADC should not be selected as an input to the GPIO in standby or sleep modes and will cause excess current con- sumption. T he GPIO settings for GPIO1 and GPIO2 are the same as for GPIO0 with the except ion of the 00000 default setting. The default settings for each GPIO are listed below: The GPIO drive strength may be adjusted with the gpioXdrv[1:0] bits. Setting a higher va lue will increase the drive strength and current capability of the GPIO by changing the driver size. Special care should be taken in setting the drive strength and loading on GPIO2 wh en the microcontroller clock is used. Excess loading or inadequate drive may contribute to increased spurious emissions. Add R/W Function/Des cription D6 D5 D4 D3 D2 D1 D0 POR Def. 0B R/W GPIO0 Configuration gpio0drv[1] gpio0drv[0] pup0 gpio0[4] gpio0[3] gpio0[2] gpio0[1] gpio0[0] 00h 0C R/W GPIO1 Configuration gpio1drv[1] gpio1drv[0] pup1 gpio1[4] gpio1[3] gpio1[2] gpio1[1] gpio1[0] 00h 0D R/W GPIO2 Configuration gpio2drv[1] gpio2drv[0] pup2 gpio2[4] gpio2[3] gpio2[2] gpio2[1] gpio2[0] 00h 0E R/W I/O Port Configuration extitst[2] extitst[1] extitst[0] itsdo dio2 dio1 dio0 00h G PIO 00000—Default Setting G PIO0 POR GPIO1 POR Inverted GPIO2 Microcontroller Clock Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
8.9. Antenna Diversity T o mitigate the problem of frequency-selective fading due to multi-path propagation, some tr ansceiver sys tems use a scheme known as antenna diversity. In this scheme, two antennas are used. Each time the transceiver en ters RX mode the receive signal strength from each antenna is evaluated. This evaluation process takes place during the preamble portion of the packet. The antenna with the stro ngest received signal is then used for the remainder of that RX packet. The same antenna will also be used for the next corresponding TX packet. This chip fully supports antenna diversity with an integrated antenna dive rsity control algorithm. The required signals needed to control an external SPDT RF switch (s uch as PIN diode or GaAs s witch) are available on the GPIOx pins. The operation of these GPIO signals is programmable to allow for different antenna diversity architectures and configurations. The antdiv[2:0] bits ar e found in register 08h “Operating & Function Control 2.” The GPIO pins are capable of sourcing up to 5 mA of curr ent, so it may be used directly to forward-bias a PIN diode if desired. The antenna diversity algorithm will automatically togg le back and forth between the antennas until the packet starts to arrive. The recommended preamble length for optimal antenna selection is 8 bytes. A special antenna diversity algorithm (antdiv[2:0] = 110 or 111) is included that allows for shorter preamble lengths for beacon mode in TDMA-like systems where the arrival of the packet is synchronous to the receiver enable. The recommended preamble length to obtain optimal antenna selection for synchronous mode is 4 bytes. Add R/W Function/Description D 7 D6 D5 D4 D3 D2 D1 D0 POR Def.
08 R/W Operating & Function
antdiv[2] antdiv[1] antdiv[0] rxmpk autotx enldm ffclrrx ffclrtx 00h T able 17. Antenna Diversity Control ant div[2:0] RX/TX State Non RX/TX State GPIO Ant1 GPIO Ant2 GPIO Ant1 GPIO Ant2 0 0 1 0 0 001 1 0 0 0 010 0 1 1 1 011 1 0 1 1
100 Antenna Diversity Algorithm 0 0
101 Antenna Diversity Algorithm 1 1
110 Antenna Diversity Algorithm in Beacon Mode 0 0
111 Antenna Diversity Algorithm in Beacon Mode 1 1
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8.10. RSSI and Clear Ch annel Assessment Received signal s trength indicator (RSSI) is an estimate of the signal strength in the channel to which the receiver is tuned. The RSSI value can be read from an 8-bit regi ster with 0.5 dB resolution per bit. Figure 31 demonstrates the relationship between input power level and RSSI value. The absolute value of the RSSI will change slightly depending on the modem settings. The RSSI may be read at anytime, but an incorrect error may rarely occur. The RSSI value may be incorrect if read during the update period. The update period is approximately 10 ns every 4 Tb. For 10 kbps, this would result in a 1 in 40,000 probability that th e RSSI may be read incorrectly. This probability is extremely low, but to avoid this, one of the following optio ns is recommended: majority polling, reading the RSSI value within 1 Tb of the RSSI interrupt, or using the RSSI threshold described in the next paragraph for Clear Channel Assessment (CCA). For CCA, threshold is programmed into rssith[7:0] in "Register 27h. RSSI Threshold fo r Clear Channel Indicator." After the RSSI is evaluated in the preamble, a decision is made if the signal strength on this channel is above or below the threshold. If the signal st rength is above the programmed threshold then the RSSI status bit, irssi, in "Register 04h. Interrupt/Status 2" will be set to 1. The RSSI status can also be routed to a GPIO line by configuring the GPIO configuration register to GPIOx[3:0] = 1110. Figure 31. RSSI Value vs. Input Power Add R/W Function/Description D7 D6 D5 D4 D3 D2 D1 D0 POR Def. R Received Signal Strength Indicator rssi[7] rssi[6] rssi[5] rssi[4] rssi[3] rssi[2] rssi[1] rssi[0] — 27 R/W RSSI Threshold for Clear Channel Indicator rssith[7] rssith [6] rssith[5] rssith[4] rssith[3] rssith[2] rssith[1] rssith[0] 00h RS SI vs Input Power 100 150 200 250 120 -100 -80 -60 -40 -20 0 20 In Pow [dBm] RS SI Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
- Reference Design Figure32A.RFM22B Reference Design Schematic Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com Figure32B.RFM23B Reference Design Schematic
- Register T able and Descriptions T able 18. Register Descriptions Ad d R/W Function/Desc Data POR DefaultD7 D6 D5 D4 D3 D2 D1 D0
00 R Device Type 0 0 0 dt[4] dt[3] dt[2] dt[1] dt[0] 00111
01 R Device Version 0 0 0 vc[4] vc[3] vc[2] vc[1] vc[0] 06h
02 R Device Status ffovfl ffunfl rxffem headerr reserved reserved cps[1] cps[0] —
05 R/W Interrupt Enable 1 enfferr entxffafull entxffaem enrxffafull enext enpksent enpkvalid encrcerror 00h
06 R/W Interrupt Enable 2 enswdet enpreaval enpreainval enrssi enwut enlbd enchiprdy enpor 03h
07 R/W Operating & Function Control 1 swres enlbd enwt x32ksel txon rxon pllon xton 01h
08 R/W Operating & Function Control 2 antdiv[2] antdiv[1] antdiv[0] rxmpk autotx enldm ffclrrx ffclrtx 00h xtalshft xlc[6] xlc[5] xlc[4] xlc[3] xlc[2] xlc[1] xlc[0] 7Fh 0A R/W Microcontroller Output Clock Reserved Reser ved clkt[1] clkt[0] enlfc mclk[2] mclk[1] mclk[0] 06h 0B R/W GPIO0 Configuration gpio0drv[1] gpio0drv[0] pup0 gpio0[4] gpio0[3] gpio0[2] gpio0[1] gpio0[0] 00h 0C R/W GPIO1 Configuration gpio1drv[1] gpio1drv[0] pup1 gpio1[4] gpio1[3] gpio1[2] gpio1[1] gpio1[0] 00h 0D R/W GPIO2 Configuration gpio2drv[1] gpio2drv[0] pup2 gpio2[4] gpio2[3] gpio2[2] gpio2[1] gpio2[0] 00h 0E R/W I/O Port Configuration Reserved extitst[2] extitst[1] extitst[0] itsdo dio2 dio1 dio0 00h 0F R/W ADC Configuration adcstart/ adc- done adcsel[2] adcsel[1] adcsel[0] adcref[1] adcref[0] adcgain[1] adcgain[0] 00h 10 R/W ADC Sensor Amplifier Offset Reserved Reserved Reserv ed Reserved adcoffs[3] adcoffs[2] adcoffs[1] adcoffs[0] 00h
11 R ADC Value adc[7] adc[6] adc[5] a dc[4] adc[3] adc[2] adc[1] adc[0] —
12 R/W Temperature Sensor Control tsrange[1] tsrange[0] entsoffs entstrim tstrim[3] tstrim[2] tstrim[1] tstrim[0] 20h 13 R/W Temperature Value Offset tvoffs[7] tvoffs[6] tvoffs[5] tvoffs[4] tvoffs[3] tvoffs[2] tvoffs[1] tvoffs[0] 00h
14 R/W Wake-Up Timer Period 1 Reserved Reserved Reserved wtr[4] wtr[3] wtr[2] wtr[1] wtr[0] 03h
15 R/W Wake-Up Timer Period 2 wtm[15] wtm[14] wtm[13] wtm[12] wtm[11] wtm[10] wtm[9] wtm[8] 00h
16 R/W Wake-Up Timer Period 3 wtm[7] wtm[6] wtm[5] wtm[4] wtm[3] wtm[2] wtm[1] wtm[0] 01h
17 R Wake-Up Timer Value 1 wtv[15] wtv[14] wtv[13] wtv[12] wtv[11] wtv[10] wtv[9] wtv[8] —
18 R Wake-Up Timer Value 2 wtv[7] wtv[6] wtv[5] wtv[4] wtv[3] wtv[2] wtv[1] wtv[0] —
19 R/W Low-Duty Cycle Mode Duration ldc[7] ldc[6] ldc[5] ldc[4] ldc[3] ldc[2] ldc[1] ldc[0] 00h
1A R/W Low Battery Detector Threshold Reserved Reserved Reserved lbdt[4] lbdt[3] lbdt[2] lbdt[1] lbdt[0] 14h 1B R Battery Voltage Level 0 0 0 vbat[4] vbat[3] vbat[2] vbat[1] vbat[0] — 1C R/W IF Filter Bandwidth dwn3_bypass ndec[2] ndec[1] ndec[0] filset[3] filset[2] filset[1] filset[0] 01h 1D R/W AFC Loop Gearshift Override afcbd enafc afcgearh[2] afcgearh[1] afcgearh[0] 1p5 bypass matap ph0size 40h 1E R/W AFC Timing Control swait_timer[1] swait_timer[0] shwait[2] shwait[1] shwait[0] anwait[2] anwait[1] anwait[0] 0Ah 1F R/W Clock Recovery Gearshift Override Reserved Reserved crfast[2] c rfast[1] crfast[0] crslow[ 2] crslow[1] crslow[0] 03h
20 R/W Clock Recovery Oversampling
rxosr[7] rxosr[6] rxosr[5] rxosr[4] rxosr[3] rxosr[ 2] rxosr[1] rxosr[0] 64h 21 R/W Clock Recovery Offset 2 rxosr[10] rxosr[9] rxosr[8] stallctrl ncoff[19] ncoff[18] ncoff[17] ncoff[16] 01h 22 R/W Clock Recovery Offset 1 ncoff[15] ncoff[14] ncoff[13] ncoff[12] ncoff[11] ncoff[10] ncoff[9] ncoff[8] 47h 23 R/W Clock Recovery Offset 0 nco ff[7] ncoff[6] ncoff[5] ncoff[4] ncoff[3] ncoff[2] ncoff[1] ncoff[0] AEh
24 R/W Clock Recovery Timing Loop
Reserved Reserved Reserved rxncocomp c rgain2x crgain[10] crgain[9] crgain[8] 02h
25 R/W Clock Recovery Timing Loop
crgain[7] crgain[6] crgain[5] crgain[4] crgain[3] crgain[2] crgain[1] crgain[0] 8Fh
26 R Received Signal Strength Indi-
rssi[7] rssi[6] rssi[5] rssi[4] rssi[3] rssi[2] rssi[1] rssi[0] —
27 R/W RSSI Threshold for Clear
rssith[7] rssith[6] rssith[5] rssith[4] rssith[3] rssith[2] rssith[1] rssith[0] 1Eh 28 R Antenna Diversity Register 1 adrssi1[7] adrssia[6] adrs sia[5] adrssia[4] adrssia[3] adrssia[2] adrssia[1] adrssia[0] — 29 R Antenna Diversity Register 2 adrssib[7] adrssib[6] adrs sib[5] adrssib[4] adrssib[3] adrssib[2] adrssib[1] adrssib[0] — 2A R/W AFC Limiter Afclim[7] Afclim[6] Afclim[5] Afclim[4] Afclim[3] Afclim[2] Afclim[1] Afclim[0] 00h 2B R AFC Correction Read afc_corr[9] afc_corr[8] afc_corr[7] afc_corr[6] afc_corr[5] afc_corr[4] afc_corr[3] afc_corr[2] 00h 2C R/W OOK Counter Value 1 afc_corr[9] afc_corr[9] ookfrzen peakdeten madeten ookcnt[10] ookcnt[9] ookcnt[8] 18h 2D R/W OOK Counter Value 2 ookcnt[7] ookcnt[6] ookcnt[5] ookcnt[4] ookcnt[3] ookcnt[2] ookcnt[1] ookcnt[0] BCh 2E R/W Slicer Peak Hold Reserved attack[2] attack[ 1] attack[0] decay[3] decay[2] decay[1] decay[0] 26h 2F Reserved
30 R/W Data Access Control enpacrx lsbfrst crcdonly skip2ph enpactx encrc crc[1] crc[0] 8Dh
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R EzMAC status 0 rxcrc1 pksrch pkrx pkvalid crcerror pktx pksent —
33 R/W Header Control 2 skipsyn hdlen[2] hdlen[1] hdlen[0] fixpklen synclen[1] synclen[0] prealen[8] 22h
34 R/W Preamble Length prealen[7] prealen[6] prealen[5] prealen[4] prealen[3] prealen[2] prealen[1] prealen[0] 08h 35 R/W Preamble Detection Control preath[4] preath[3] preath[2] preath[1] preath[0] rssi_off[2] rssi_off[1] rssi_off[0] 2Ah
38 R/W Sync Word 1 sync[15] sync[14] sync[13] sync[12] sync[11] sync[ 10] sync[9] sync[8] 00h
39 R/W Sync Word 0 sync[7] sync[6] sync[5] sync[4] sync[3] sync[2] sync[1] sync[0] 00h
3A R/W Transmit Header 3 txhd[31] txhd[30] txhd[2 9] txhd[28] txhd[27] txhd[26] txhd[25] txhd[24] 00h 3B R/W Transmit Header 2 txhd[23] txhd[22] txhd[2 1] txhd[20] txhd[19] txhd[18] txhd[17] txhd[16] 00h 3C R/W Transmit Header 1 txhd[15] txhd[14] txhd [13] txhd[12] txhd[11] txhd[10] txhd[9] txhd[8] 00h 3D R/W Transmit Header 0 txhd[7] txhd[6] tx hd[5] txhd[4] txhd[3] txhd[2] txhd[1] txhd[0] 00h 3E R/W Transmit Packet Length pklen[7] pklen[6] pklen[ 5] pklen[4] pklen[3] pklen[2] pklen[1] pklen[0] 00h 3F R/W Check Header 3 chhd[31] chhd[30] chhd[29] chhd[28] chhd[27] chhd[26] chhd[25] chhd[24] 00h
47 R Received Header 3 rxhd[31] rxhd[30] rxhd[29] rxhd[28] rxhd[27] rxhd[26] rxhd[25] rxhd[24] —
48 R Received Header 2 rxhd[23] rxhd[22] rxhd[21] rxhd[20] rxhd[19] rxhd[18] rxhd[17] rxhd[16] —
49 R Received Header 1 rxhd[15] rxhd[14] rxhd[13] rxhd[12] rxhd[11] rxhd[10] rxhd[9] rxhd[8] —
4A R Received Header 0 rxhd[7] rxhd[6] rxhd[5] rxhd[4] rxhd[3] rxhd[2] rxhd[1] rxhd[0] — 4B R Received Packet Length rxplen[7] rxplen[6] rxplen [5] rxplen[4] rxplen[3] rxplen[2] rxplen[1] rxplen[0] — 4C-4E Reserved 4F R/W ADC8 Control Reserved Reserved adc8[5] adc8[4] adc8[3] adc8[2] adc8[1] adc8[0] 10h 50-5F Reserved
60 R/W Channel Filter Coefficient
Inv_pre_th[3] Inv_pre_th[2] Inv_pre_th[1] Inv_pre_th[0] chfiladd[3] chfiladd[2] chfiladd[1] chfiladd[0] 00h
61 Reserved
62 R/W Crystal Oscillator/Control Test pwst[2] pwst[1] pwst[0] clkhyst enbias2x enamp2x bufovr enbuf 24h
69 R/W AGC Override 1 Reserved sgi agcen lnagain pga3 pga2 pga1 pga0 20h
6D R/W TX Power papeakval papeaken papeaklvl[1] pap eaklvl[0] Ina_sw txpow[2] txpow[1] txpow[0] 18h 6E R/W TX Data Rate 1 txdr[15] txdr[14] txdr[13] txdr[12] txdr[11] txdr[10] txdr[9] txdr[8] 0Ah 6F R/W TX Data Rate 0 txdr[7] txdr[6] txdr[5] txdr[4] txdr[3] txdr[2] txdr[1] txdr[0] 3Dh 70 R/W Modulation Mode Control 1 Reserved Reserved txdtrtscale enphpwdn manppol enmaninv enmanch enwhite 0Ch
71 R/W Modulation Mode Control 2 trclk[1] trclk[0] dtmod[1] dtmod[0] eninv fd[8] modtyp[1] modtyp[0] 00h
72 R/W Frequency Deviation fd[7] fd[6] fd[5] fd[4] fd[3] fd[2] fd[1] fd[0] 20h
74 R/W Frequency Offset 2 Reserved Reserved Res erved Reserved Reserved Reserved fo[9] fo[8] 00h
75 R/W Frequency Band Select Reserved sbsel hbsel fb[4] fb[3] fb[2] fb[1] fb[0] 75h
76 R/W Nominal Carrier Frequency 1 fc[15] fc[14] fc[13] fc[12] fc[11] fc[10] fc[9] fc[8] BBh
77 R/W Nominal Carrier Frequency 0 fc[7] fc[6] fc[5] fc[4] fc[3] fc[2] fc[1] fc[0] 80h
78 Reserved
fhch[7] fhch[6] fhch[5] fhch[4] fhch[3] fhch[2] fhch[1] fhch[0] 00h 7A R/W Frequency Hopping Step Size fhs[7] fhs[6] fhs[5] fhs[4] fhs[3] fhs[2] fhs[1] fhs[0] 00h 7B Reserved 7C R/W TX FIFO Control 1 Reserved Reserved txafthr[5] txafthr[4] txafthr[3] txafthr[2] txafthr[1] txafthr[0] 37h 7D R/W TX FIFO Control 2 Reserved Reserved txaethr[5] tx aethr[4] txaethr[3] txaethr[2] txaethr[1] txaethr[0] 04h 7E R/W RX FIFO Control Reserved Reserved rxafthr[5] rxafthr[4] rxafthr[3] rxafthr[2] rxafthr[1] rxafthr[0] 37h 7F R/W FIFO Access fifod[7] fifod[6] fifod[5] fifod[4] fifod[3] fifod[2] fifod[1] fifod[0] — T able 18. Register Descriptions (Continued) Ad d R/W Function/Desc Data POR DefaultD7 D6 D5 D4 D3 D2 D1 D0 Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com
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11.1 Pin Descriptions:RFM22B
Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf .com VCC S +1.8 to +3.6 V supply voltage. The recommended V CC supply voltage is +3.3 V. GND S Ground reference. GPIO_0 I/O GPIO_1 I/O GPIO_2 I/O General Purpose Digital I/O that may be configured through the registers to perform various functions including: Microcontroller Clock Output, FIFO status, POR, Wake-Up timer, Low Battery Detect, TRSW, AntDiversity control, etc. See the SPI GPIO Configuration Registers, Address 0Bh, 0Ch, and 0Dh for more information. SDO O 0–V CC V digital output that pr ovides a serial readback function of the internal control registers. SDI I Serial Data input. 0–V CC V digital input. This pin provides the serial data stream for the 4-line serial data bus. SCLK I Serial Clock input. 0–V DD V digital input. This pin provides the serial data clock function for the 4-line serial data bus. Data is clocked into the RFM22 on positive edge transitions. nSEL I Serial Interface Select input. 0– V CC V digital input. This pin provides the Select/Enable function for the 4-line serial data bus. The signal is also used to signify burst read/write mode. nIRQ O General Microcontroller Interr upt Status outpu t. When the RFM22 exhibits anyone of the Interrupt Events the nIRQ pin will be set low=0. Please see the Control Logic registers section for more information on the Interrupt Events. The Microcontroller can then determine the state of the interrupt by reading a corresponding SPI Interrupt Status Registers, Address 03h and 04h. SDN I Shutdown input pin. 0–V CC V digital input. SDN should be = 0 in all modes except Shutdown mode. When SDN =1 the chip will be completely shutdown and the contents of the registers will be lost. TX_ANT I Tx Antenna select input pin, Wh en RFM22 is TX state,TX_ANT should be = 1, RX_ANT should be = 0 RX_ANT I Rx Antenna select input pin, When RFM2 2 is RX state,RX_ANT should be = 1, TX_ANT should be = 0 ANT I/O RF signal output/input.(50 OHM output /input Impedance
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11.2 Pin Descriptions: RFM23B
Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com VCC S +1.8 to +3.6 V supply voltage. The recommended V CC supply voltage is +3.3 V. GND S Ground reference. GPIO_0 I/O GPIO_1 I/O GPIO_2 I/O General Purpose Digital I/O that may be configured through the registers to perform various functions including: Microcontroller Clock Output, FIFO status, POR, Wake-Up timer, Low Battery Detect, TRSW, AntDiversity control, etc. See the SPI GPIO Configuration Registers, Address 0Bh, 0Ch, and 0Dh for more information. SDO O 0–V CC V digital output that pro vides a serial readback function of the internal control registers. SDI I Serial Data input. 0–V CC V digital input. This pin provides the serial data stream for the 4-line serial data bus. SCLK I Serial Clock input. 0–V DD V digital input. This pin provides the serial data clock function for the 4-line serial data bus. Data is clocked into the RFM23A on positive edge transitions. nSEL I Serial Interface Select input. 0– V CC V digital input. This pin provides the Select/Enable function for the 4-line serial data bus. The signal is also used to signify burst read/write mode. nIRQ O General Microcontroller Interrupt Status output. W hen the RFM23A exhibits anyone of the Interrupt Events the nIRQ pin will be set low=0. Please see the Control Logic registers section for more information on the Interrupt Events. The Microcontroller can then determine the state of the interrupt by reading a corresponding SPI Interrupt Status Registers, Address 03h and 04h. SDN I Shutdown input pin. 0–V CC V digital input. SDN should be = 0 in all modes except Shutdown mode. When SDN =1 the chip will be completely shutdown and the contents of the registers will be lost. NC NC ANT I/O RF signal output/input.(50 OHM output /input Impedance
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12.1 Mechanical Dimension:RFM22B
SMD PACKAGE（S1） SMD PACKAGE（S2）
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12.2 Mechanical Dimension:RFM23B
SMD PACKAGE（S1） SMD PACKAGE（S2）
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Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com http://www.hoperf.com 14. Ordering Information Part Number=module type—operation band—package type RFM22B—433—D module type operation band Pac kage example：1，RFM22B module at 433MHz band, DIP : RFM22B-433-D。 2，RFM22B module at 868MHZ band, SMD, thickness at 4.9mm: RFM22B-868-S1。
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Table 20. PCB Land Pattern Dimensions
- All dimensions shown are in millimeters (mm) unless otherwise noted.
- This land pattern design is based on IPC-7351 guidelines.
- All metal pads are to be non-solder mask defined (NSMD). Clearance
- A stainless steel, laser-cut and electro-polished stencil with trapezoidal
walls should be used to assure good solder paste release.
- The stencil thickness should be 0.125 mm (5 mils).
- The ratio of stencil aperture to land pad size should be 1:1 for
- A 2x2 array of 1.10 x 1.10 mm openings on 1.30 mm pitch should
be used for the center ground pad.
- A No-Clean, Type-3 solder paste is recommended.
- The recommended card reflow profile is per the JEDEC/IPC J-STD-020
specification for small body components.
LECTRONICS CO.,LTD Add:4/F, Block B3, East Industrial Area, Huaqiaocheng, Shenzhen, Guangdong, China Tel: 86-755-82973805 Fax: 86-755-82973550 Email: sales@hoperf.com trade@hoperf.com Web site: http://www.hope rf.com http://hoperf.en.a libaba.com This document ma y contain preliminary information and is subject to change by Hope Microelectronics w ithout notice. Hope Microelectronics assumes no responsibility or liability for any use of the information contained herein. Nothing in this document shall operate as an expr ess or implied license or indemnity under the intellectual property rights of Hope Microelectronics or third parties. The product s described in this document are not intended for use in implantation or ot her direct life support applications where malfunction may result in the direct phy sical harm or injury to persons. NO WARRANTIES OF ANY KIND, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MECHANTABILITY OR FITNESS FOR A ARTICULAR PURPOSE, ARE OFFERED IN THIS DOCUMENT. ©2006, HOPE MICROELECTRONICS CO.,LTD. All rights reserved. Tel: +86-755-82973805 Fax: +86-755-82973550 E-mail: sales@hoperf.com ht tp://www.hoperf.com