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 timeUs_t frameTime = 0;
  75
  76 // Receive ISR callback
  77 static void sbusDataReceive(uint16_t c, void *data)
  78 {
  79     sbusFrameData_t *sbusFrameData = data;
  80     const timeUs_t currentTimeUs = micros();
  81     const timeDelta_t timeSinceLastByteUs = cmpTimeUs(currentTimeUs, sbusFrameData->lastActivityTimeUs);
  82     sbusFrameData->lastActivityTimeUs = currentTimeUs;
  83
  84     // 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
  85     if (timeSinceLastByteUs >= rxConfig()->sbusSyncInterval) {
  86         sbusFrameData->state = STATE_SBUS_SYNC;
  87     } else if ((sbusFrameData->state == STATE_SBUS_PAYLOAD || sbusFrameData->state == STATE_SBUS26_PAYLOAD) && timeSinceLastByteUs >= 300) {
  88         // payload is pausing too long, possible if some telemetry have been sent between frames
  89         sbusFrameData->state = STATE_SBUS_SYNC;
  90     }
  91
  92     switch (sbusFrameData->state) {
  93         case STATE_SBUS_SYNC:
  94             if (c == SBUS_FRAME_BEGIN_BYTE) {
  95                 sbusFrameData->position = 0;
  96                 sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
  97                 sbusFrameData->state = STATE_SBUS_PAYLOAD;
  98             } else if ((uint8_t)c == SBUS26_FRAME_BEGIN_BYTE) {
  99                 sbusFrameData->position = 0;
 100                 sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 101                 sbusFrameData->state = STATE_SBUS26_PAYLOAD;
 102             }
 103             break;
 104
 105         case STATE_SBUS_PAYLOAD:
 106             sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 107
 108             if (sbusFrameData->position == SBUS_FRAME_SIZE) {
 109                 const sbusFrame_t * frame = (sbusFrame_t *)&sbusFrameData->buffer[0];
 110                 bool frameValid = false;
 111
 112                 // Do some sanity check
 113                 switch (frame->endByte) {
 114                     case 0x00:  // This is S.BUS 1
 115                     case 0x04:  // S.BUS 2 telemetry page 1
 116                     case 0x14:  // S.BUS 2 telemetry page 2
 117                     case 0x24:  // S.BUS 2 telemetry page 3
 118                     case 0x34:  // S.BUS 2 telemetry page 4
 119                         if(frame->endByte & 0x4) {
 120                             sbus2ActiveTelemetryPage = (frame->endByte >> 4) & 0xF;
 121                             frameTime = currentTimeUs;
 122                         } else {
 123                             sbus2ActiveTelemetryPage = 0;
 124                             sbus2ActiveTelemetrySlot = 0;
 125                             frameTime = -1;
 126                         }
 127
 128                         frameValid = true;
 129                         sbusFrameData->state = STATE_SBUS_WAIT_SYNC;
 130                         break;
 131
 132                     default:    // Failed end marker
 133                         sbusFrameData->state = STATE_SBUS_WAIT_SYNC;
 134                         break;
 135                 }
 136
 137                 // Frame seems sane, pass data to decoder
 138                 if (!sbusFrameData->frameDone && frameValid) {
 139
 140                     memcpy((void *)&sbusFrameData->frame, (void *)&sbusFrameData->buffer[0], SBUS_FRAME_SIZE);
 141                     sbusFrameData->frameDone = true;
 142                 }
 143             }
 144             break;
 145
 146         case STATE_SBUS26_PAYLOAD:
 147             sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 148
 149             if (sbusFrameData->position == SBUS_FRAME_SIZE) {
 150                 const sbusFrame_t * frame = (sbusFrame_t *)&sbusFrameData->buffer[0];
 151                 bool frameValid = false;
 152
 153                 // Do some sanity check
 154                 switch (frame->endByte) {
 155                     case 0x00:
 156                     case 0x04:  // S.BUS 2 telemetry page 1
 157                     case 0x14:  // S.BUS 2 telemetry page 2
 158                     case 0x24:  // S.BUS 2 telemetry page 3
 159                     case 0x34:  // S.BUS 2 telemetry page 4
 160                         frameTime = -1; // ignore this one, as you can't fit telemetry between this and the next frame.
 161                         frameValid = true;
 162                         sbusFrameData->state = STATE_SBUS_SYNC; // Next piece of data should be a sync byte
 163                         break;
 164
 165                     default:    // Failed end marker
 166                         frameValid = false;
 167                         sbusFrameData->state = STATE_SBUS_WAIT_SYNC;
 168                         break;
 169                 }
 170
 171                 // Frame seems sane, pass data to decoder
 172                 if (!sbusFrameData->frameDone && frameValid) {
 173                     memcpy((void *)&sbusFrameData->frameHigh, (void *)&sbusFrameData->buffer[0], SBUS_FRAME_SIZE);
 174                     sbusFrameData->frameDone = true;
 175                     sbusFrameData->is26channels = true;
 176                 }
 177             }
 178             break;
 179
 180         case STATE_SBUS_WAIT_SYNC:
 181             // Stay at this state and do nothing. Exit will be handled before byte is processed if the
 182             // inter-frame gap is long enough
 183             if (c == SBUS26_FRAME_BEGIN_BYTE || c == 0xF2 || c == 0x2c) {
 184                 sbusFrameData->position = 0;
 185                 sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 186                 sbusFrameData->state = STATE_SBUS26_PAYLOAD;
 187             }
 188
 189             break;
 190     }
 191 }
 192
 193 static uint8_t sbusFrameStatus(rxRuntimeConfig_t *rxRuntimeConfig)
 194 {
 195     sbusFrameData_t *sbusFrameData = rxRuntimeConfig->frameData;
 196
 197     if (!sbusFrameData->frameDone) {
 198         return RX_FRAME_PENDING;
 199     }
 200
 201     uint8_t retValue = 0;
 202     // Decode channel data and store return value
 203     if (sbusFrameData->is26channels)
 204     {
 205         retValue = sbus26ChannelsDecode(rxRuntimeConfig, (void *)&sbusFrameData->frame.channels, false);
 206         retValue |= sbus26ChannelsDecode(rxRuntimeConfig, (void *)&sbusFrameData->frameHigh.channels, true);
 207
 208     } else {
 209         retValue = sbusChannelsDecode(rxRuntimeConfig, (void *)&sbusFrameData->frame.channels);
 210     }
 211
 212     // Reset the frameDone flag - tell ISR that we're ready to receive next frame
 213     sbusFrameData->frameDone = false;
 214
 215     // Calculate "virtual link quality based on packet loss metric"
 216     if (retValue & RX_FRAME_COMPLETE) {
 217         lqTrackerAccumulate(rxRuntimeConfig->lqTracker, ((retValue & RX_FRAME_DROPPED) || (retValue & RX_FRAME_FAILSAFE)) ? 0 : RSSI_MAX_VALUE);
 218     }
 219
 220     return retValue;
 221 }
 222
 223 static bool sbusInitEx(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig, uint32_t sbusBaudRate)
 224 {
 225     static uint16_t sbusChannelData[SBUS_MAX_CHANNEL];
 226     static sbusFrameData_t sbusFrameData = { .is26channels = false};
 227
 228     rxRuntimeConfig->channelData = sbusChannelData;
 229     rxRuntimeConfig->frameData = &sbusFrameData;
 230
 231     sbusChannelsInit(rxRuntimeConfig);
 232
 233     rxRuntimeConfig->channelCount = SBUS_MAX_CHANNEL;
 234
 235     rxRuntimeConfig->rcFrameStatusFn = sbusFrameStatus;
 236
 237     const serialPortConfig_t *portConfig = findSerialPortConfig(FUNCTION_RX_SERIAL);
 238     if (!portConfig) {
 239         return false;
 240     }
 241
 242 #ifdef USE_TELEMETRY
 243     bool portShared = telemetryCheckRxPortShared(portConfig);
 244 #else
 245     bool portShared = false;
 246 #endif
 247
 248     serialPort_t *sBusPort = openSerialPort(portConfig->identifier,
 249         FUNCTION_RX_SERIAL,
 250         sbusDataReceive,
 251         &sbusFrameData,
 252         sbusBaudRate,
 253         (portShared || rxConfig->serialrx_provider == SERIALRX_SBUS2) ? MODE_RXTX : MODE_RX,
 254         SBUS_PORT_OPTIONS |
 255             (rxConfig->serialrx_inverted ? 0 : SERIAL_INVERTED) |
 256             ((rxConfig->serialrx_provider == SERIALRX_SBUS2) ? SERIAL_BIDIR : 0) |
 257             (tristateWithDefaultOffIsActive(rxConfig->halfDuplex) ? SERIAL_BIDIR : 0)
 258         );
 259
 260 #ifdef USE_TELEMETRY
 261     if (portShared || (rxConfig->serialrx_provider == SERIALRX_SBUS2)) {
 262         telemetrySharedPort = sBusPort;
 263     }
 264 #endif
 265
 266     return sBusPort != NULL;
 267 }
 268
 269 bool sbusInit(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig)
 270 {
 271     return sbusInitEx(rxConfig, rxRuntimeConfig, SBUS_BAUDRATE);
 272 }
 273
 274 bool sbusInitFast(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig)
 275 {
 276     return sbusInitEx(rxConfig, rxRuntimeConfig, SBUS_BAUDRATE_FAST);
 277 }
 278
 279 #if defined(USE_TELEMETRY) && defined(USE_TELEMETRY_SBUS2)
 280 timeUs_t sbusGetLastFrameTime(void) {
 281     return frameTime;
 282 }
 283
 284 uint8_t sbusGetCurrentTelemetryNextSlot(void)
 285 {
 286     uint8_t current = sbus2ActiveTelemetrySlot;
 287     sbus2ActiveTelemetrySlot++;
 288     return current;
 289 }
 290
 291 uint8_t sbusGetCurrentTelemetryPage(void) {
 292     return sbus2ActiveTelemetryPage;
 293 }
 294 #endif // USE_TELEMETRY && USE_SBUS2_TELEMETRY
 295
 296 #endif // USE_SERIAL_RX