src/main/rx/sbus.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 #include <string.h>
  22
  23 #include "platform.h"
  24
  25 #ifdef USE_SERIAL_RX
  26
  27 #include "build/debug.h"
  28
  29 #include "common/utils.h"
  30
  31 #include "drivers/time.h"
  32
  33 #include "io/serial.h"
  34
  35 #ifdef USE_TELEMETRY
  36 #include "telemetry/telemetry.h"
  37 #endif
  38
  39 #include "rx/rx.h"
  40 #include "rx/sbus.h"
  41 #include "rx/sbus_channels.h"
  42
  43 /*
  44  * Observations
  45  *
  46  * FrSky X8R
  47  * time between frames: 6ms.
  48  * time to send frame: 3ms.
  49 *
  50  * Futaba R6208SB/R6303SB
  51  * time between frames: 11ms.
  52  * time to send frame: 3ms.
  53  */
  54 typedef enum {
  55     STATE_SBUS_SYNC = 0,
  56     STATE_SBUS_PAYLOAD,
  57     STATE_SBUS26_PAYLOAD,
  58     STATE_SBUS_WAIT_SYNC
  59 } sbusDecoderState_e;
  60
  61 typedef struct sbusFrameData_s {
  62     sbusDecoderState_e state;
  63     volatile sbusFrame_t frame;
  64     volatile sbusFrame_t frameHigh;
  65     volatile bool frameDone;
  66     volatile bool is26channels;
  67     uint8_t buffer[SBUS_FRAME_SIZE];
  68     uint8_t position;
  69     timeUs_t lastActivityTimeUs;
  70 } sbusFrameData_t;
  71
  72 static uint8_t sbus2ActiveTelemetryPage = 0;
  73 static uint8_t sbus2ActiveTelemetrySlot = 0;
  74 static uint8_t sbus2ShortFrameInterval = 0;
  75 timeUs_t frameTime = 0;
  76
  77 // Receive ISR callback
  78 static void sbusDataReceive(uint16_t c, void *data)
  79 {
  80     sbusFrameData_t *sbusFrameData = data;
  81     const timeUs_t currentTimeUs = micros();
  82     const timeDelta_t timeSinceLastByteUs = cmpTimeUs(currentTimeUs, sbusFrameData->lastActivityTimeUs);
  83     sbusFrameData->lastActivityTimeUs = currentTimeUs;
  84
  85     const int32_t syncInterval = sbus2ShortFrameInterval
  86                                      ? ((6300 - SBUS_BYTE_TIME_US(25)) / 2)
  87                                      : rxConfig()->sbusSyncInterval;
  88
  89
  90     // Handle inter-frame gap. We dwell in STATE_SBUS_WAIT_SYNC state ignoring all incoming bytes until we get long enough quite period on the wire
  91     if ((sbusFrameData->state == STATE_SBUS_WAIT_SYNC && timeSinceLastByteUs >= syncInterval)
  92             || (rxConfig()->serialrx_provider == SERIALRX_SBUS2 && timeSinceLastByteUs >= SBUS_BYTE_TIME_US(3))) {
  93         sbusFrameData->state = STATE_SBUS_SYNC;
  94     } else if ((sbusFrameData->state == STATE_SBUS_PAYLOAD || sbusFrameData->state == STATE_SBUS26_PAYLOAD) && timeSinceLastByteUs >= SBUS_BYTE_TIME_US(3)) {
  95         // payload is pausing too long, possible if some telemetry have been sent between frames, or false positves mid frame
  96         sbusFrameData->state = STATE_SBUS_SYNC;
  97     }
  98
  99     switch (sbusFrameData->state) {
 100         case STATE_SBUS_SYNC:
 101             if (c == SBUS_FRAME_BEGIN_BYTE) {
 102                 sbusFrameData->position = 0;
 103                 sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 104                 sbusFrameData->state = STATE_SBUS_PAYLOAD;
 105             } else if (c == SBUS2_HIGHFRAME_BEGIN_BYTE) {
 106                 sbusFrameData->position = 0;
 107                 sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 108                 sbusFrameData->state = STATE_SBUS26_PAYLOAD;
 109             }
 110             break;
 111
 112         case STATE_SBUS_PAYLOAD:
 113             sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 114
 115             if (sbusFrameData->position == SBUS_FRAME_SIZE) {
 116                 const sbusFrame_t * frame = (sbusFrame_t *)&sbusFrameData->buffer[0];
 117                 bool frameValid = false;
 118
 119                 // Do some sanity check
 120                 switch (frame->endByte) {
 121                     case 0x00:  // This is S.BUS 1
 122                     case 0x04:  // S.BUS 2 telemetry page 1
 123                     case 0x08:  // S.BUS 2 fast frame pace, not telemetry.
 124                     case 0x14:  // S.BUS 2 telemetry page 2
 125                     case 0x24:  // S.BUS 2 telemetry page 3
 126                     case 0x34:  // S.BUS 2 telemetry page 4
 127                         if(frame->endByte & 0x4) {
 128                             sbus2ActiveTelemetryPage = (frame->endByte >> 4) & 0xF;
 129                             frameTime = currentTimeUs;
 130                         } else if(frame->endByte == 0x08) {
 131                             sbus2ShortFrameInterval = 1;
 132                         } else {
 133                             sbus2ActiveTelemetryPage = 0;
 134                             sbus2ActiveTelemetrySlot = 0;
 135                             frameTime = -1;
 136                         }
 137
 138                         frameValid = true;
 139                         sbusFrameData->state = STATE_SBUS_WAIT_SYNC;
 140                         break;
 141
 142                     default:    // Failed end marker
 143                         sbusFrameData->state = STATE_SBUS_WAIT_SYNC;
 144                         break;
 145                 }
 146
 147                 // Frame seems sane, pass data to decoder
 148                 if (!sbusFrameData->frameDone && frameValid) {
 149
 150                     memcpy((void *)&sbusFrameData->frame, (void *)&sbusFrameData->buffer[0], SBUS_FRAME_SIZE);
 151                     sbusFrameData->frameDone = true;
 152                 }
 153             }
 154             break;
 155
 156         case STATE_SBUS26_PAYLOAD:
 157             sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 158
 159             if (sbusFrameData->position == SBUS_FRAME_SIZE) {
 160                 const sbusFrame_t * frame = (sbusFrame_t *)&sbusFrameData->buffer[0];
 161                 bool frameValid = false;
 162
 163                 // Do some sanity check
 164                 switch (frame->endByte) {
 165                     case 0x00:
 166                     case 0x04:  // S.BUS 2 telemetry page 1
 167                     case 0x14:  // S.BUS 2 telemetry page 2
 168                     case 0x24:  // S.BUS 2 telemetry page 3
 169                     case 0x34:  // S.BUS 2 telemetry page 4
 170                         frameTime = -1; // ignore this one, as you can't fit telemetry between this and the next frame.
 171                         frameValid = true;
 172                         sbusFrameData->state = STATE_SBUS_SYNC; // Next piece of data should be a sync byte
 173                         break;
 174
 175                     default:    // Failed end marker
 176                         frameValid = false;
 177                         sbusFrameData->state = STATE_SBUS_WAIT_SYNC;
 178                         break;
 179                 }
 180
 181                 // Frame seems sane, pass data to decoder
 182                 if (!sbusFrameData->frameDone && frameValid) {
 183                     memcpy((void *)&sbusFrameData->frameHigh, (void *)&sbusFrameData->buffer[0], SBUS_FRAME_SIZE);
 184                     sbusFrameData->frameDone = true;
 185                     sbusFrameData->is26channels = true;
 186                 }
 187             }
 188             break;
 189
 190         case STATE_SBUS_WAIT_SYNC:
 191             // Stay at this state and do nothing. Exit will be handled before byte is processed if the
 192             // inter-frame gap is long enough
 193             break;
 194     }
 195 }
 196
 197 static uint8_t sbusFrameStatus(rxRuntimeConfig_t *rxRuntimeConfig)
 198 {
 199     sbusFrameData_t *sbusFrameData = rxRuntimeConfig->frameData;
 200
 201     if (!sbusFrameData->frameDone) {
 202         return RX_FRAME_PENDING;
 203     }
 204
 205     uint8_t retValue = 0;
 206     // Decode channel data and store return value
 207     if (sbusFrameData->is26channels)
 208     {
 209         retValue = sbus26ChannelsDecode(rxRuntimeConfig, (void *)&sbusFrameData->frame.channels, false);
 210         retValue |= sbus26ChannelsDecode(rxRuntimeConfig, (void *)&sbusFrameData->frameHigh.channels, true);
 211
 212     } else {
 213         retValue = sbusChannelsDecode(rxRuntimeConfig, (void *)&sbusFrameData->frame.channels);
 214     }
 215
 216     // Reset the frameDone flag - tell ISR that we're ready to receive next frame
 217     sbusFrameData->frameDone = false;
 218
 219     // Calculate "virtual link quality based on packet loss metric"
 220     if (retValue & RX_FRAME_COMPLETE) {
 221         lqTrackerAccumulate(rxRuntimeConfig->lqTracker, ((retValue & RX_FRAME_DROPPED) || (retValue & RX_FRAME_FAILSAFE)) ? 0 : RSSI_MAX_VALUE);
 222     }
 223
 224     return retValue;
 225 }
 226
 227 static bool sbusInitEx(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig, uint32_t sbusBaudRate)
 228 {
 229     static uint16_t sbusChannelData[SBUS_MAX_CHANNEL];
 230     static sbusFrameData_t sbusFrameData = { .is26channels = false};
 231
 232     rxRuntimeConfig->channelData = sbusChannelData;
 233     rxRuntimeConfig->frameData = &sbusFrameData;
 234
 235     sbusChannelsInit(rxRuntimeConfig);
 236
 237     rxRuntimeConfig->channelCount = SBUS_MAX_CHANNEL;
 238
 239     rxRuntimeConfig->rcFrameStatusFn = sbusFrameStatus;
 240
 241     const serialPortConfig_t *portConfig = findSerialPortConfig(FUNCTION_RX_SERIAL);
 242     if (!portConfig) {
 243         return false;
 244     }
 245
 246 #ifdef USE_TELEMETRY
 247     bool portShared = telemetryCheckRxPortShared(portConfig);
 248 #else
 249     bool portShared = false;
 250 #endif
 251
 252     serialPort_t *sBusPort = openSerialPort(portConfig->identifier,
 253         FUNCTION_RX_SERIAL,
 254         sbusDataReceive,
 255         &sbusFrameData,
 256         sbusBaudRate,
 257         (portShared || rxConfig->serialrx_provider == SERIALRX_SBUS2) ? MODE_RXTX : MODE_RX,
 258         SBUS_PORT_OPTIONS |
 259             (rxConfig->serialrx_inverted ? 0 : SERIAL_INVERTED) |
 260             ((rxConfig->serialrx_provider == SERIALRX_SBUS2) ? SERIAL_BIDIR : 0) |
 261             (tristateWithDefaultOffIsActive(rxConfig->halfDuplex) ? SERIAL_BIDIR : 0)
 262         );
 263
 264 #ifdef USE_TELEMETRY
 265     if (portShared || (rxConfig->serialrx_provider == SERIALRX_SBUS2)) {
 266         telemetrySharedPort = sBusPort;
 267     }
 268 #endif
 269
 270     return sBusPort != NULL;
 271 }
 272
 273 bool sbusInit(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig)
 274 {
 275     return sbusInitEx(rxConfig, rxRuntimeConfig, SBUS_BAUDRATE);
 276 }
 277
 278 bool sbusInitFast(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig)
 279 {
 280     return sbusInitEx(rxConfig, rxRuntimeConfig, SBUS_BAUDRATE_FAST);
 281 }
 282
 283 #if defined(USE_TELEMETRY) && defined(USE_TELEMETRY_SBUS2)
 284 timeUs_t sbusGetLastFrameTime(void) {
 285     return frameTime;
 286 }
 287
 288 uint8_t sbusGetCurrentTelemetryNextSlot(void)
 289 {
 290     uint8_t current = sbus2ActiveTelemetrySlot;
 291     sbus2ActiveTelemetrySlot++;
 292     return current;
 293 }
 294
 295 uint8_t sbusGetCurrentTelemetryPage(void) {
 296     return sbus2ActiveTelemetryPage;
 297 }
 298 #endif // USE_TELEMETRY && USE_SBUS2_TELEMETRY
 299
 300 #endif // USE_SERIAL_RX