src/main/rx/xbus.c

   1 /*
   2  * This file is part of Cleanflight.
   3  *
   4  * Cleanflight is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * Cleanflight is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with Cleanflight.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include <stdbool.h>
  19 #include <stdint.h>
  20 #include <stdlib.h>
  21
  22 #include "platform.h"
  23
  24 #include "drivers/system.h"
  25
  26 #include "drivers/serial.h"
  27 #include "drivers/serial_uart.h"
  28 #include "io/serial.h"
  29
  30 #include "rx/rx.h"
  31 #include "rx/xbus.h"
  32
  33 //
  34 // Serial driver for JR's XBus (MODE B) receiver
  35 //
  36
  37 #define XBUS_CHANNEL_COUNT 12
  38 #define XBUS_RJ01_CHANNEL_COUNT 12
  39
  40 // Frame is: ID(1 byte) + 12*channel(2 bytes) + CRC(2 bytes) = 27
  41 #define XBUS_FRAME_SIZE 27
  42
  43 #define XBUS_RJ01_FRAME_SIZE 33
  44 #define XBUS_RJ01_MESSAGE_LENGTH 30
  45 #define XBUS_RJ01_OFFSET_BYTES 3
  46
  47 #define XBUS_CRC_AND_VALUE 0x8000
  48 #define XBUS_CRC_POLY 0x1021
  49
  50 #define XBUS_BAUDRATE 115200
  51 #define XBUS_RJ01_BAUDRATE 250000
  52 #define XBUS_MAX_FRAME_TIME 8000
  53
  54 // NOTE!
  55 // This is actually based on ID+LENGTH (nibble each)
  56 // 0xA - Multiplex ID (also used by JR, no idea why)
  57 // 0x1 - 12 channels
  58 // 0x2 - 16 channels
  59 // However, the JR XG14 that is used for test at the moment
  60 // does only use 0xA1 as its output. This is why the implementation
  61 // is based on these numbers only. Maybe update this in the future?
  62 #define XBUS_START_OF_FRAME_BYTE (0xA1)
  63
  64 // Pulse length convertion from [0...4095] to µs:
  65 //      800µs  -> 0x000
  66 //      1500µs -> 0x800
  67 //      2200µs -> 0xFFF
  68 // Total range is: 2200 - 800 = 1400 <==> 4095
  69 // Use formula: 800 + value * 1400 / 4096 (i.e. a shift by 12)
  70 #define XBUS_CONVERT_TO_USEC(V) (800 + ((V * 1400) >> 12))
  71
  72 static bool xBusFrameReceived = false;
  73 static bool xBusDataIncoming = false;
  74 static uint8_t xBusFramePosition;
  75 static uint8_t xBusFrameLength;
  76 static uint8_t xBusChannelCount;
  77 static uint8_t xBusProvider;
  78
  79
  80 // Use max values for ram areas
  81 static volatile uint8_t xBusFrame[XBUS_RJ01_FRAME_SIZE];
  82 static uint16_t xBusChannelData[XBUS_RJ01_CHANNEL_COUNT];
  83
  84 static void xBusDataReceive(uint16_t c);
  85 static uint16_t xBusReadRawRC(rxRuntimeConfig_t *rxRuntimeConfig, uint8_t chan);
  86
  87 bool xBusInit(rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig, rcReadRawDataPtr *callback)
  88 {
  89     uint32_t baudRate;
  90
  91     switch (rxConfig->serialrx_provider) {
  92         case SERIALRX_XBUS_MODE_B:
  93             rxRuntimeConfig->channelCount = XBUS_CHANNEL_COUNT;
  94             xBusFrameReceived = false;
  95             xBusDataIncoming = false;
  96             xBusFramePosition = 0;
  97             baudRate = XBUS_BAUDRATE;
  98             xBusFrameLength = XBUS_FRAME_SIZE;
  99             xBusChannelCount = XBUS_CHANNEL_COUNT;
 100             xBusProvider = SERIALRX_XBUS_MODE_B;
 101             break;
 102         case SERIALRX_XBUS_MODE_B_RJ01:
 103             rxRuntimeConfig->channelCount = XBUS_RJ01_CHANNEL_COUNT;
 104             xBusFrameReceived = false;
 105             xBusDataIncoming = false;
 106             xBusFramePosition = 0;
 107             baudRate = XBUS_RJ01_BAUDRATE;
 108             xBusFrameLength = XBUS_RJ01_FRAME_SIZE;
 109             xBusChannelCount = XBUS_RJ01_CHANNEL_COUNT;
 110             xBusProvider = SERIALRX_XBUS_MODE_B_RJ01;
 111             break;
 112         default:
 113             return false;
 114             break;
 115     }
 116
 117     if (callback) {
 118         *callback = xBusReadRawRC;
 119     }
 120
 121     serialPortConfig_t *portConfig = findSerialPortConfig(FUNCTION_RX_SERIAL);
 122     if (!portConfig) {
 123         return false;
 124     }
 125
 126     serialPort_t *xBusPort = openSerialPort(portConfig->identifier, FUNCTION_RX_SERIAL, xBusDataReceive, baudRate, MODE_RX, SERIAL_NOT_INVERTED);
 127
 128     return xBusPort != NULL;
 129 }
 130
 131 // The xbus mode B CRC calculations
 132 static uint16_t xBusCRC16(uint16_t crc, uint8_t value)
 133 {
 134     uint8_t i;
 135
 136     crc = crc ^ (int16_t)value << 8;
 137
 138     for (i = 0; i < 8; i++) {
 139         if (crc & XBUS_CRC_AND_VALUE) {
 140             crc = crc << 1 ^ XBUS_CRC_POLY;
 141         } else {
 142             crc = crc << 1;
 143         }
 144     }
 145     return crc;
 146 }
 147
 148 // Full RJ01 message CRC calculations
 149 uint8_t xBusRj01CRC8(uint8_t inData, uint8_t seed)
 150 {
 151     uint8_t bitsLeft;
 152     uint8_t temp;
 153
 154     for (bitsLeft = 8; bitsLeft > 0; bitsLeft--) {
 155         temp = ((seed ^ inData) & 0x01);
 156
 157         if (temp == 0) {
 158             seed >>= 1;
 159         } else {
 160             seed ^= 0x18;
 161             seed >>= 1;
 162             seed |= 0x80;
 163         }
 164
 165         inData >>= 1;
 166     }
 167
 168     return seed;
 169 }
 170
 171
 172 static void xBusUnpackModeBFrame(uint8_t offsetBytes)
 173 {
 174     // Calculate the CRC of the incoming frame
 175     uint16_t crc = 0;
 176     uint16_t inCrc = 0;
 177     uint8_t i = 0;
 178     uint16_t value;
 179     uint8_t frameAddr;
 180
 181     // Calculate on all bytes except the final two CRC bytes
 182     for (i = 0; i < XBUS_FRAME_SIZE - 2; i++) {
 183         inCrc = xBusCRC16(inCrc, xBusFrame[i+offsetBytes]);
 184     }
 185
 186     // Get the received CRC
 187     crc = ((uint16_t)xBusFrame[offsetBytes + XBUS_FRAME_SIZE - 2]) << 8;
 188     crc = crc + ((uint16_t)xBusFrame[offsetBytes + XBUS_FRAME_SIZE - 1]);
 189
 190     if (crc == inCrc) {
 191         // Unpack the data, we have a valid frame
 192         for (i = 0; i < xBusChannelCount; i++) {
 193
 194             frameAddr = offsetBytes + 1 + i * 2;
 195             value = ((uint16_t)xBusFrame[frameAddr]) << 8;
 196             value = value + ((uint16_t)xBusFrame[frameAddr + 1]);
 197
 198             // Convert to internal format
 199             xBusChannelData[i] = XBUS_CONVERT_TO_USEC(value);
 200         }
 201
 202         xBusFrameReceived = true;
 203     }
 204
 205 }
 206
 207 static void xBusUnpackRJ01Frame(void)
 208 {
 209     // Calculate the CRC of the incoming frame
 210     uint8_t outerCrc = 0;
 211     uint8_t i = 0;
 212
 213     // When using the Align RJ01 receiver with
 214     // a MODE B setting in the radio (XG14 tested)
 215     // the MODE_B -frame is packed within some
 216     // at the moment unknown bytes before and after:
 217     // 0xA1 LEN __ 0xA1 12*(High + Low) CRC1 CRC2 + __ __ CRC_OUTER
 218     // Compared to a standard MODE B frame that only
 219     // contains the "middle" package.
 220     // Hence, at the moment, the unknown header and footer
 221     // of the RJ01 MODEB packages are discarded.
 222     // However, the LAST byte (CRC_OUTER) is infact an 8-bit
 223     // CRC for the whole package, using the Dallas-One-Wire CRC
 224     // method.
 225     // So, we check both these values as well as the provided length
 226     // of the outer/full message (LEN)
 227
 228     //
 229     // Check we have correct length of message
 230     //
 231     if (xBusFrame[1] != XBUS_RJ01_MESSAGE_LENGTH)
 232     {
 233         // Unknown package as length is not ok
 234         return;
 235     }
 236
 237     //
 238     // CRC calculation & check for full message
 239     //
 240     for (i = 0; i < xBusFrameLength - 1; i++) {
 241         outerCrc = xBusRj01CRC8(outerCrc, xBusFrame[i]);
 242     }
 243
 244     if (outerCrc != xBusFrame[xBusFrameLength - 1])
 245     {
 246         // CRC does not match, skip this frame
 247         return;
 248     }
 249
 250     // Now unpack the "embedded MODE B frame"
 251     xBusUnpackModeBFrame(XBUS_RJ01_OFFSET_BYTES);
 252 }
 253
 254 // Receive ISR callback
 255 static void xBusDataReceive(uint16_t c)
 256 {
 257     uint32_t now;
 258     static uint32_t xBusTimeLast, xBusTimeInterval;
 259
 260     // Check if we shall reset frame position due to time
 261     now = micros();
 262     xBusTimeInterval = now - xBusTimeLast;
 263     xBusTimeLast = now;
 264     if (xBusTimeInterval > XBUS_MAX_FRAME_TIME) {
 265         xBusFramePosition = 0;
 266         xBusDataIncoming = false;
 267     }
 268
 269     // Check if we shall start a frame?
 270     if ((xBusFramePosition == 0) && (c == XBUS_START_OF_FRAME_BYTE)) {
 271         xBusDataIncoming = true;
 272     }
 273
 274     // Only do this if we are receiving to a frame
 275     if (xBusDataIncoming == true) {
 276         // Store in frame copy
 277         xBusFrame[xBusFramePosition] = (uint8_t)c;
 278         xBusFramePosition++;
 279     }
 280
 281     // Done?
 282     if (xBusFramePosition == xBusFrameLength) {
 283         switch (xBusProvider) {
 284             case SERIALRX_XBUS_MODE_B:
 285                 xBusUnpackModeBFrame(0);
 286             case SERIALRX_XBUS_MODE_B_RJ01:
 287                 xBusUnpackRJ01Frame();
 288         }
 289         xBusDataIncoming = false;
 290         xBusFramePosition = 0;
 291     }
 292 }
 293
 294 // Indicate time to read a frame from the data...
 295 uint8_t xBusFrameStatus(void)
 296 {
 297     if (!xBusFrameReceived) {
 298         return SERIAL_RX_FRAME_PENDING;
 299     }
 300
 301     xBusFrameReceived = false;
 302
 303     return SERIAL_RX_FRAME_COMPLETE;
 304 }
 305
 306 static uint16_t xBusReadRawRC(rxRuntimeConfig_t *rxRuntimeConfig, uint8_t chan)
 307 {
 308     uint16_t data;
 309
 310     // Deliver the data wanted
 311     if (chan >= rxRuntimeConfig->channelCount) {
 312         return 0;
 313     }
 314
 315     data = xBusChannelData[chan];
 316
 317     return data;
 318 }