Library to send and receive data using RF12B transceiver modules Big thanks to the tutorial at https://loee.jottit.com/rfm12b_and_avr_-_quick_start and madcowswe
Dependents: Measure_system Quadcopter_copy
RF12B.cpp
- Committer:
- harryeakins
- Date:
- 2011-03-11
- Revision:
- 8:6fc24b44e027
- Parent:
- 7:9f9e2a63a8a2
- Child:
- 9:cd34784da6da
File content as of revision 8:6fc24b44e027:
#include "RF12B.h" #include "RF_defs.h" #include <algorithm> RF12B::RF12B(PinName _SDI, PinName _SDO, PinName _SCK, PinName _NCS, PinName _NIRQ):spi(_SDI, _SDO, _SCK), NCS(_NCS), NIRQ(_NIRQ), NIRQ_in(_NIRQ), rfled(LED3) { /* SPI frequency, word lenght, polarity and phase */ spi.format(16,0); spi.frequency(2000000); /* Set ~CS high */ NCS = 1; /* Initialise RF Module */ init(); /* Setup interrupt to happen on falling edge of NIRQ */ NIRQ.fall(this, &RF12B::rxISR); } /* Returns the packet length if data is available in the receive buffer, 0 otherwise*/ unsigned int RF12B::available() { return fifo.size(); } /* Reads a packet of data, with length "size" Returns false if read failed. TODO: make a metafifo to isolate packets*/ bool RF12B::read(unsigned char* data, unsigned int size) { if (fifo.size() == 0) { return false; } else { unsigned int i = 0; while (fifo.size() > 0 && i < size) { data[i++] = fifo.front(); fifo.pop(); } return true; } } /* Reads a byte of data from the receive buffer */ unsigned char RF12B::read() { if (available()) { unsigned char data = fifo.front(); fifo.pop(); return data; } else { return 0xFF; // Error val although could also be data... } } /* Sends a packet of data to the RF module for transmission TODO: Make asych*/ void RF12B::write(unsigned char *data, unsigned char length) { unsigned char crc = 0; /* Transmitter mode */ changeMode(TX); writeCmd(0x0000); send(0xAA); // PREAMBLE send(0xAA); send(0xAA); send(0x2D); // SYNC send(0xD4); /* Packet Length */ send(length); crc = crc8(crc, length); send(crc); crc = crc8(crc, crc); /* Packet Data */ for (unsigned char i=0; i<length; i++) { send(data[i]); crc = crc8(crc, data[i]); } send(crc); send(0xAA); // DUMMY BYTES send(0xAA); send(0xAA); /* Back to receiver mode */ changeMode(RX); status(); } /* Transmit a 1-byte data packet */ void RF12B::write(unsigned char data) { write(&data, 1); } void RF12B::write(queue<char> &data, int length) { char crc = 0; char length_byte = 0; /* -1 means try to transmit everything in the queue */ if(length == -1) { length = data.size(); } /* max length of packet is 255 */ length_byte = min(length, 255); /* Transmitter mode */ changeMode(TX); writeCmd(0x0000); send(0xAA); // PREAMBLE send(0xAA); send(0xAA); send(0x2D); // SYNC send(0xD4); /* Packet Length */ send(length_byte); crc = crc8(crc, length_byte); send(crc); crc = crc8(crc, crc); /* Packet Data */ for (char i=0; i<length_byte; i++) { send(data.front()); crc = crc8(crc, data.front()); data.pop(); } send(crc); send(0xAA); // DUMMY BYTES send(0xAA); send(0xAA); /* Back to receiver mode */ changeMode(RX); status(); } /********************************************************************** * PRIVATE FUNCTIONS *********************************************************************/ /* Initialises the RF12B module */ void RF12B::init() { /* writeCmd(0x80E7); //EL,EF,868band,12.0pF changeMode(RX); writeCmd(0xA640); //frequency select writeCmd(0xC647); //4.8kbps writeCmd(0x94A0); //VDI,FAST,134kHz,0dBm,-103dBm writeCmd(0xC2AC); //AL,!ml,DIG,DQD4 writeCmd(0xCA81); //FIFO8,SYNC,!ff,DR writeCmd(0xCED4); //SYNC=2DD4 writeCmd(0xC483); //@PWR,NO RSTRIC,!st,!fi,OE,EN writeCmd(0x9850); //!mp,90kHz,MAX OUT writeCmd(0xCC17); //OB1, COB0, LPX, Iddy, CDDIT�CBW0 writeCmd(0xE000); //NOT USED writeCmd(0xC800); //NOT USED writeCmd(0xC040); //1.66MHz,2.2V */ writeCmd( RFM_CONFIG_EL | RFM_CONFIG_EF | RFM_CONFIG_BAND_433 //| //RFM_CONFIG_X_11_0pf // meh, using default ); // 2. Power Management Command // leave everything switched off for now /* writeCmd( RFM_POWER_MANAGEMENT // switch all off ); */ // 3. Frequency Setting Command writeCmd( RFM_FREQUENCY | RFM_FREQ_433Band(435.7) //I totally made this value up... if someone knows where the sweetspots are in this band, tell me! ); // 4. Data Rate Command writeCmd(RFM_DATA_RATE_9600); // 5. Receiver Control Command writeCmd( RFM_RX_CONTROL_P20_VDI | RFM_RX_CONTROL_VDI_FAST | //RFM_RX_CONTROL_BW(RFM_BAUD_RATE) | RFM_RX_CONTROL_BW_134 | // CHANGE THIS TO 67 TO IMPROVE RANGE! (though the bitrate must then be below 8kbaud, and fsk modulation changed) RFM_RX_CONTROL_GAIN_0 | RFM_RX_CONTROL_RSSI_103 // Might need adjustment. Datasheet says around 10^-5 bit error rate at this level and baudrate. ); // 6. Data Filter Command writeCmd( RFM_DATA_FILTER_AL | RFM_DATA_FILTER_ML | RFM_DATA_FILTER_DIG //| //RFM_DATA_FILTER_DQD(4) ); // 7. FIFO and Reset Mode Command writeCmd( RFM_FIFO_IT(8) | RFM_FIFO_DR | 0x8 //turn on 16bit sync word ); // 8. FIFO Syncword // Leave as default: 0xD4 // 9. Receiver FIFO Read // when the interupt goes high, (and if we can assume that it was a fifo fill interrupt) we can read a byte using: // result = RFM_READ_FIFO(); // 10. AFC Command writeCmd( //RFM_AFC_AUTO_VDI | //Note this might be changed to improve range. Refer to datasheet. RFM_AFC_AUTO_INDEPENDENT | RFM_AFC_RANGE_LIMIT_7_8 | RFM_AFC_EN | RFM_AFC_OE | RFM_AFC_FI ); // 11. TX Configuration Control Command writeCmd( RFM_TX_CONTROL_MOD_60 | RFM_TX_CONTROL_POW_0 ); // 12. PLL Setting Command writeCmd( 0xCC77 & ~0x01 // Setting the PLL bandwith, less noise, but max bitrate capped at 86.2 // I think this will slow down the pll's reaction time. Not sure, check with someone! ); resetRX(); status(); } /* Write a command to the RF Module */ unsigned int RF12B::writeCmd(unsigned int cmd) { NCS = 0; unsigned int recv = spi.write(cmd); NCS = 1; return recv; } /* Sends a byte of data across RF */ void RF12B::send(unsigned char data) { while (NIRQ); writeCmd(0xB800 + data); } /* Change the mode of the RF module to Transmitting or Receiving */ void RF12B::changeMode(rfmode_t _mode) { mode = _mode; if (_mode == TX) { writeCmd(0x8239); //!er,!ebb,ET,ES,EX,!eb,!ew,DC } else { /* mode == RX */ writeCmd(0x8299); //er,!ebb,ET,ES,EX,!eb,!ew,DC } } /* Interrupt routine for data reception */ void RF12B::rxISR() { unsigned int data = 0; static int i = -2; static unsigned char packet_length = 0; static unsigned char crc = 0; static queue<unsigned char> temp; //Loop while interrupt is asserted while (!NIRQ_in && mode == RX) { /* Grab the packet's length byte */ if (i == -2) { data = writeCmd(0x0000); if ( (data&0x8000) ) { data = writeCmd(0xB000); packet_length = (data&0x00FF); crc = crc8(crc, packet_length); i++; } } //If we exhaust the interrupt, exit if (NIRQ_in) break; // Check that packet length was correct if (i == -1) { data = writeCmd(0x0000); if ( (data&0x8000) ) { data = writeCmd(0xB000); unsigned char crcofsize = (data&0x00FF); if (crcofsize != crc) { //It was wrong, start over i = -2; packet_length = 0; crc = 0; temp = queue<unsigned char>(); resetRX(); } else { crc = crc8(crc, crcofsize); i++; } } } //If we exhaust the interrupt, exit if (NIRQ_in) break; /* Grab the packet's data */ if (i >= 0 && i < packet_length) { data = writeCmd(0x0000); if ( (data&0x8000) ) { data = writeCmd(0xB000); temp.push(data&0x00FF); crc = crc8(crc, (unsigned char)(data&0x00FF)); i++; } } //If we exhaust the interrupt, exit if (NIRQ_in) break; if (i >= packet_length) { data = writeCmd(0x0000); if ( (data&0x8000) ) { data = writeCmd(0xB000); if ((unsigned char)(data & 0x00FF) == crc) { //If the checksum is correct, add our data to the end of the output buffer while (!temp.empty()) { fifo.push(temp.front()); temp.pop(); } } /* Tell RF Module we are finished, and clean up */ i = -2; packet_length = 0; crc = 0; temp = queue<unsigned char>(); resetRX(); } } } } unsigned int RF12B::status() { return writeCmd(0x0000); } /* Tell the RF Module this packet is received and wait for the next */ void RF12B::resetRX() { writeCmd(0xCA81); writeCmd(0xCA83); }; /* Calculate CRC8 */ unsigned char RF12B::crc8(unsigned char crc, unsigned char data) { crc = crc ^ data; for (int i = 0; i < 8; i++) { if (crc & 0x01) { crc = (crc >> 1) ^ 0x8C; } else { crc >>= 1; } } return crc; }