RF12B.cpp

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