RF12B.cpp

00001 #include "RF12B.h"
00002 
00003 #include "RF_defs.h"
00004 #include <algorithm>
00005 
00006 
00007 RF12B::RF12B(PinName _SDI,
00008              PinName _SDO,
00009              PinName _SCK,
00010              PinName _NCS,
00011              PinName _NIRQ):spi(_SDI, _SDO, _SCK),
00012         NCS(_NCS), NIRQ(_NIRQ), NIRQ_in(_NIRQ), rfled(LED3) {
00013 
00014     /* SPI frequency, word lenght, polarity and phase */
00015     spi.format(16,0);
00016     spi.frequency(2000000);
00017 
00018     /* Set ~CS high */
00019     NCS = 1;
00020 
00021     /* Initialise RF Module */
00022     init();
00023 
00024     /* Setup interrupt to happen on falling edge of NIRQ */
00025     NIRQ.fall(this, &RF12B::rxISR);
00026 }
00027 
00028 /* Returns the packet length if data is available in the receive buffer, 0 otherwise*/
00029 unsigned int RF12B::available() {
00030     return fifo.size();
00031 }
00032 
00033 /* Reads a packet of data, with length "size" Returns false if read failed. TODO: make a metafifo to isolate packets*/
00034 bool RF12B::read(unsigned char* data, unsigned int size) {
00035     if (fifo.size() == 0) {
00036         return false;
00037     } else {
00038         unsigned int i = 0;
00039         while (fifo.size() > 0 && i < size) {
00040             data[i++] = fifo.front();
00041             fifo.pop();
00042         }
00043         return true;
00044     }
00045 }
00046 
00047 /* Reads a byte of data from the receive buffer */
00048 unsigned char RF12B::read() {
00049     if (available()) {
00050         unsigned char data = fifo.front();
00051         fifo.pop();
00052         return data;
00053     } else {
00054         return 0xFF; // Error val although could also be data...
00055     }
00056 }
00057 
00058 /* Sends a packet of data to the RF module for transmission TODO: Make asych*/
00059 void RF12B::write(unsigned char *data, unsigned char length) {
00060     unsigned char crc = 0;
00061        
00062     /* Transmitter mode */
00063     changeMode(TX);
00064 
00065     writeCmd(0x0000);
00066     send(0xAA); // PREAMBLE
00067     send(0xAA);
00068     send(0xAA);
00069     send(0x2D); // SYNC
00070     send(0xD4);
00071     /* Packet Length */
00072     send(length);
00073     crc = crc8(crc, length);
00074     send(crc);
00075     crc = crc8(crc, crc);
00076     /* Packet Data */
00077     for (unsigned char i=0; i<length; i++) {
00078         send(data[i]);
00079         crc = crc8(crc, data[i]);
00080     }
00081     send(crc);
00082     send(0xAA); // DUMMY BYTES
00083     send(0xAA);
00084     send(0xAA);
00085 
00086     /* Back to receiver mode */
00087     changeMode(RX);
00088     status();
00089     
00090 
00091 }
00092 
00093 /* Transmit a 1-byte data packet */
00094 void RF12B::write(unsigned char data) {
00095     write(&data, 1);
00096 }
00097 
00098 void RF12B::write(queue<char> &data, int length) {
00099     char crc = 0;
00100     char length_byte = 0;
00101     
00102     /* -1 means try to transmit everything in the queue */
00103     if(length == -1) {
00104         length = data.size();
00105     }
00106     
00107     /* max length of packet is 255 */
00108     length_byte = min(length, 255);
00109     
00110     /* Transmitter mode */
00111     changeMode(TX);
00112 
00113     writeCmd(0x0000);
00114     send(0xAA); // PREAMBLE
00115     send(0xAA);
00116     send(0xAA);
00117     send(0x2D); // SYNC
00118     send(0xD4);
00119     /* Packet Length */
00120     send(length_byte);
00121     crc = crc8(crc, length_byte);
00122     send(crc);
00123     crc = crc8(crc, crc);
00124     /* Packet Data */
00125     for (char i=0; i<length_byte; i++) {
00126         send(data.front());
00127         crc = crc8(crc, data.front());
00128         data.pop();
00129     }
00130     send(crc);
00131     send(0xAA); // DUMMY BYTES
00132     send(0xAA);
00133     send(0xAA);
00134 
00135     /* Back to receiver mode */
00136     changeMode(RX);
00137     status();
00138 }
00139 
00140 /**********************************************************************
00141  *  PRIVATE FUNCTIONS
00142  *********************************************************************/
00143 
00144 /* Initialises the RF12B module */
00145 void RF12B::init() {
00146     /* writeCmd(0x80E7); //EL,EF,868band,12.0pF
00147      changeMode(RX);
00148      writeCmd(0xA640); //frequency select
00149      writeCmd(0xC647); //4.8kbps
00150      writeCmd(0x94A0); //VDI,FAST,134kHz,0dBm,-103dBm
00151      writeCmd(0xC2AC); //AL,!ml,DIG,DQD4
00152      writeCmd(0xCA81); //FIFO8,SYNC,!ff,DR
00153      writeCmd(0xCED4); //SYNC=2DD4
00154      writeCmd(0xC483); //@PWR,NO RSTRIC,!st,!fi,OE,EN
00155      writeCmd(0x9850); //!mp,90kHz,MAX OUT
00156      writeCmd(0xCC17); //OB1, COB0, LPX, Iddy, CDDIT&#65533;CBW0
00157      writeCmd(0xE000); //NOT USED
00158      writeCmd(0xC800); //NOT USED
00159      writeCmd(0xC040); //1.66MHz,2.2V */
00160 
00161     writeCmd(
00162         RFM_CONFIG_EL           |
00163         RFM_CONFIG_EF           |
00164         RFM_CONFIG_BAND_433     //|
00165         //RFM_CONFIG_X_11_0pf // meh, using default
00166     );
00167 
00168     // 2. Power Management Command
00169     // leave everything switched off for now
00170     /*
00171     writeCmd(
00172         RFM_POWER_MANAGEMENT     // switch all off
00173     );
00174     */
00175 
00176     // 3. Frequency Setting Command
00177     writeCmd(
00178         RFM_FREQUENCY            |
00179         RFM_FREQ_433Band(435.7)  //I totally made this value up... if someone knows where the sweetspots are in this band, tell me!
00180     );
00181 
00182 
00183     // 4. Data Rate Command
00184     writeCmd(RFM_DATA_RATE_9600);
00185 
00186 
00187     // 5. Receiver Control Command
00188     writeCmd(
00189         RFM_RX_CONTROL_P20_VDI  |
00190         RFM_RX_CONTROL_VDI_FAST |
00191         //RFM_RX_CONTROL_BW(RFM_BAUD_RATE) |
00192         RFM_RX_CONTROL_BW_134   |     // CHANGE THIS TO 67 TO IMPROVE RANGE! (though the bitrate must then be below 8kbaud, and fsk modulation changed)
00193         RFM_RX_CONTROL_GAIN_0   |
00194         RFM_RX_CONTROL_RSSI_103      // Might need adjustment. Datasheet says around 10^-5 bit error rate at this level and baudrate.
00195     );
00196 
00197     // 6. Data Filter Command
00198     writeCmd(
00199         RFM_DATA_FILTER_AL      |
00200         RFM_DATA_FILTER_ML      |
00201         RFM_DATA_FILTER_DIG     //|
00202         //RFM_DATA_FILTER_DQD(4)
00203     );
00204 
00205     // 7. FIFO and Reset Mode Command
00206     writeCmd(
00207         RFM_FIFO_IT(8) |
00208         RFM_FIFO_DR    |
00209         0x8 //turn on 16bit sync word
00210     );
00211 
00212     // 8. FIFO Syncword
00213     // Leave as default: 0xD4
00214 
00215     // 9. Receiver FIFO Read
00216     // when the interupt goes high, (and if we can assume that it was a fifo fill interrupt) we can read a byte using:
00217     // result = RFM_READ_FIFO();
00218 
00219     // 10. AFC Command
00220     writeCmd(
00221         //RFM_AFC_AUTO_VDI        |  //Note this might be changed to improve range. Refer to datasheet.
00222         RFM_AFC_AUTO_INDEPENDENT    |
00223         RFM_AFC_RANGE_LIMIT_7_8     |
00224         RFM_AFC_EN                  |
00225         RFM_AFC_OE                  |
00226         RFM_AFC_FI
00227     );
00228 
00229     // 11. TX Configuration Control Command
00230     writeCmd(
00231         RFM_TX_CONTROL_MOD_60 |
00232         RFM_TX_CONTROL_POW_0
00233     );
00234 
00235 
00236     // 12. PLL Setting Command
00237     writeCmd(
00238         0xCC77 & ~0x01 // Setting the PLL bandwith, less noise, but max bitrate capped at 86.2
00239         // I think this will slow down the pll's reaction time. Not sure, check with someone!
00240     );
00241 
00242     changeMode(RX);
00243     resetRX();
00244     status();
00245 }
00246 
00247 /* Write a command to the RF Module */
00248 unsigned int RF12B::writeCmd(unsigned int cmd) {
00249     NCS = 0;
00250     unsigned int recv = spi.write(cmd);
00251     NCS = 1;
00252     return recv;
00253 }
00254 
00255 /* Sends a byte of data across RF */
00256 void RF12B::send(unsigned char data) {
00257     while (NIRQ);
00258     writeCmd(0xB800 + data);
00259 }
00260 
00261 /* Change the mode of the RF module to Transmitting or Receiving */
00262 void RF12B::changeMode(rfmode_t _mode) {
00263     mode = _mode;
00264     if (_mode == TX) {
00265         writeCmd(0x8239); //!er,!ebb,ET,ES,EX,!eb,!ew,DC
00266     } else { /* mode == RX */
00267         writeCmd(0x8299); //er,!ebb,ET,ES,EX,!eb,!ew,DC
00268     }
00269 }
00270 
00271 /* Interrupt routine for data reception */
00272 void RF12B::rxISR() {
00273     unsigned int data = 0;
00274     static int i = -2;
00275     static unsigned char packet_length = 0;
00276     static unsigned char crc = 0;
00277     static queue<unsigned char> temp;
00278 
00279     //Loop while interrupt is asserted
00280     while (!NIRQ_in && mode == RX) {
00281 
00282         /* Grab the packet's length byte */
00283         if (i == -2) {
00284             data = writeCmd(0x0000);
00285             if ( (data&0x8000) ) {
00286                 data = writeCmd(0xB000);
00287                 packet_length = (data&0x00FF);
00288                 crc = crc8(crc, packet_length);
00289                 i++;
00290             }
00291         }
00292 
00293         //If we exhaust the interrupt, exit
00294         if (NIRQ_in)
00295             break;
00296 
00297         // Check that packet length was correct
00298         if (i == -1) {
00299             data = writeCmd(0x0000);
00300             if ( (data&0x8000) ) {
00301                 data = writeCmd(0xB000);
00302                 unsigned char crcofsize = (data&0x00FF);
00303                 if (crcofsize != crc) {
00304                     //It was wrong, start over
00305                     i = -2;
00306                     packet_length = 0;
00307                     crc = 0;
00308                     temp = queue<unsigned char>();
00309                     resetRX();
00310                 } else {
00311                     crc = crc8(crc, crcofsize);
00312                     i++;
00313                 }
00314             }
00315         }
00316 
00317         //If we exhaust the interrupt, exit
00318         if (NIRQ_in)
00319             break;
00320 
00321         /* Grab the packet's data */
00322         if (i >= 0 && i < packet_length) {
00323             data = writeCmd(0x0000);
00324             if ( (data&0x8000) ) {
00325                 data = writeCmd(0xB000);
00326                 temp.push(data&0x00FF);
00327                 crc = crc8(crc, (unsigned char)(data&0x00FF));
00328                 i++;
00329             }
00330         }
00331 
00332         //If we exhaust the interrupt, exit
00333         if (NIRQ_in)
00334             break;
00335 
00336         if (i >= packet_length) {
00337             data = writeCmd(0x0000);
00338             if ( (data&0x8000) ) {
00339                 data = writeCmd(0xB000);
00340                 if ((unsigned char)(data & 0x00FF) == crc) {
00341                     //If the checksum is correct, add our data to the end of the output buffer
00342                     while (!temp.empty()) {
00343                         fifo.push(temp.front());
00344                         temp.pop();
00345                     }
00346                 }
00347 
00348                 /* Tell RF Module we are finished, and clean up */
00349                 i = -2;
00350                 packet_length = 0;
00351                 crc = 0;
00352                 temp = queue<unsigned char>();
00353                 resetRX();
00354             }
00355         }
00356     }
00357 }
00358 
00359 unsigned int RF12B::status() {
00360     return writeCmd(0x0000);
00361 }
00362 
00363 /* Tell the RF Module this packet is received and wait for the next */
00364 void RF12B::resetRX() {
00365     writeCmd(0xCA81);
00366     writeCmd(0xCA83);
00367 };
00368 
00369 /* Calculate CRC8 */
00370 unsigned char RF12B::crc8(unsigned char crc, unsigned char data) {
00371     crc = crc ^ data;
00372     for (int i = 0; i < 8; i++) {
00373         if (crc & 0x01) {
00374             crc = (crc >> 1) ^ 0x8C;
00375         } else {
00376             crc >>= 1;
00377         }
00378     }
00379     return crc;
00380 }