File content as of revision 6:98da0571ec31:

#include "RF12B.h"

#include "RF_defs.h"

DigitalOut rfled(LED3);

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 true if receive buffer contains data */
bool RF12B::available() {
    return !fifo.empty();
}

/* 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 */
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);
    /* 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);
}

/**********************************************************************
 *  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 plls 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) {
    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, i = 0;
    unsigned char packet_length = 0;
    unsigned char crc = 0;
    queue<unsigned char> temp;

    /* Grab the packet's length byte */
    data = writeCmd(0x0000);
    if ( (data&0x8000) ) {
        data = writeCmd(0xB000);
        packet_length = (data&0x00FF);
        crc = crc8(crc, packet_length);
    }

    /* Grab the packet's data */
    while (i < packet_length) {
        if (!NIRQ_in) {
            data = writeCmd(0x0000);
            if ( (data&0x8000) ) {
                data = writeCmd(0xB000);
                temp.push(data&0x00FF);
                crc = crc8(crc, (unsigned char)(data&0x00FF));
                i++;
            }
        }
    }
    while (1) {
        if (!NIRQ_in) {
            data = writeCmd(0x0000);
            if ( (data&0x8000) ) {
                data = writeCmd(0xB000);
                if ((unsigned char)(data & 0x00FF) == crc) {
                    while (!temp.empty()) {
                        fifo.push(temp.front());
                        temp.pop();
                    }
                }
                break;
            }
        }
    }
    /* Tell RF Module we are finished */
    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;
}