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 FILE_COMPILE_FOR_SPEED
  25
  26 #ifdef USE_SERIAL_RX
  27
  28 #include "build/debug.h"
  29
  30 #include "common/utils.h"
  31
  32 #include "drivers/time.h"
  33
  34 #include "io/serial.h"
  35
  36 #ifdef USE_TELEMETRY
  37 #include "telemetry/telemetry.h"
  38 #endif
  39
  40 #include "rx/rx.h"
  41 #include "rx/sbus.h"
  42 #include "rx/sbus_channels.h"
  43
  44 /*
  45  * Observations
  46  *
  47  * FrSky X8R
  48  * time between frames: 6ms.
  49  * time to send frame: 3ms.
  50 *
  51  * Futaba R6208SB/R6303SB
  52  * time between frames: 11ms.
  53  * time to send frame: 3ms.
  54  */
  55
  56 enum {
  57     DEBUG_SBUS_INTERFRAME_TIME = 0,
  58     DEBUG_SBUS_FRAME_FLAGS = 1,
  59     DEBUG_SBUS_DESYNC_COUNTER = 2
  60 };
  61
  62 typedef enum {
  63     STATE_SBUS_SYNC = 0,
  64     STATE_SBUS_PAYLOAD,
  65     STATE_SBUS_WAIT_SYNC
  66 } sbusDecoderState_e;
  67
  68 typedef struct sbusFrameData_s {
  69     sbusDecoderState_e state;
  70     volatile sbusFrame_t frame;
  71     volatile bool frameDone;
  72     uint8_t buffer[SBUS_FRAME_SIZE];
  73     uint8_t position;
  74     timeUs_t lastActivityTimeUs;
  75 } sbusFrameData_t;
  76
  77 // Receive ISR callback
  78 static void sbusDataReceive(uint16_t c, void *data)
  79 {
  80     static uint16_t sbusDesyncCounter = 0;
  81
  82     sbusFrameData_t *sbusFrameData = data;
  83     const timeUs_t currentTimeUs = micros();
  84     const timeDelta_t timeSinceLastByteUs = cmpTimeUs(currentTimeUs, sbusFrameData->lastActivityTimeUs);
  85     sbusFrameData->lastActivityTimeUs = currentTimeUs;
  86
  87     // 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
  88     if (sbusFrameData->state == STATE_SBUS_WAIT_SYNC && timeSinceLastByteUs >= rxConfig()->sbusSyncInterval) {
  89         DEBUG_SET(DEBUG_SBUS, DEBUG_SBUS_INTERFRAME_TIME, timeSinceLastByteUs);
  90         sbusFrameData->state = STATE_SBUS_SYNC;
  91     }
  92
  93     switch (sbusFrameData->state) {
  94         case STATE_SBUS_SYNC:
  95             if (c == SBUS_FRAME_BEGIN_BYTE) {
  96                 sbusFrameData->position = 0;
  97                 sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
  98                 sbusFrameData->state = STATE_SBUS_PAYLOAD;
  99             }
 100             break;
 101
 102         case STATE_SBUS_PAYLOAD:
 103             sbusFrameData->buffer[sbusFrameData->position++] = (uint8_t)c;
 104
 105             if (sbusFrameData->position == SBUS_FRAME_SIZE) {
 106                 const sbusFrame_t * frame = (sbusFrame_t *)&sbusFrameData->buffer[0];
 107                 bool frameValid = false;
 108
 109                 // Do some sanity check
 110                 switch (frame->endByte) {
 111                     case 0x00:  // This is S.BUS 1
 112                     case 0x04:  // S.BUS 2 receiver voltage
 113                     case 0x14:  // S.BUS 2 GPS/baro
 114                     case 0x24:  // Unknown SBUS2 data
 115                     case 0x34:  // Unknown SBUS2 data
 116                         frameValid = true;
 117                         sbusFrameData->state = STATE_SBUS_WAIT_SYNC;
 118                         break;
 119
 120                     default:    // Failed end marker
 121                         sbusFrameData->state = STATE_SBUS_WAIT_SYNC;
 122                         sbusDesyncCounter++;
 123                         DEBUG_SET(DEBUG_SBUS, DEBUG_SBUS_DESYNC_COUNTER, sbusDesyncCounter);
 124                         break;
 125                 }
 126
 127                 // Frame seems sane, pass data to decoder
 128                 if (!sbusFrameData->frameDone && frameValid) {
 129                     DEBUG_SET(DEBUG_SBUS, DEBUG_SBUS_FRAME_FLAGS, frame->channels.flags);
 130
 131                     memcpy((void *)&sbusFrameData->frame, (void *)&sbusFrameData->buffer[0], SBUS_FRAME_SIZE);
 132                     sbusFrameData->frameDone = true;
 133                 }
 134             }
 135             break;
 136
 137         case STATE_SBUS_WAIT_SYNC:
 138             // Stay at this state and do nothing. Exit will be handled before byte is processed if the
 139             // inter-frame gap is long enough
 140             break;
 141     }
 142 }
 143
 144 static uint8_t sbusFrameStatus(rxRuntimeConfig_t *rxRuntimeConfig)
 145 {
 146     sbusFrameData_t *sbusFrameData = rxRuntimeConfig->frameData;
 147
 148     if (!sbusFrameData->frameDone) {
 149         return RX_FRAME_PENDING;
 150     }
 151
 152     // Decode channel data and store return value
 153     const uint8_t retValue = sbusChannelsDecode(rxRuntimeConfig, (void *)&sbusFrameData->frame.channels);
 154
 155     // Reset the frameDone flag - tell ISR that we're ready to receive next frame
 156     sbusFrameData->frameDone = false;
 157
 158     // Calculate "virtual link quality based on packet loss metric"
 159     if (retValue & RX_FRAME_COMPLETE) {
 160         lqTrackerAccumulate(rxRuntimeConfig->lqTracker, ((retValue & RX_FRAME_DROPPED) || (retValue & RX_FRAME_FAILSAFE)) ? 0 : RSSI_MAX_VALUE);
 161     }
 162
 163     return retValue;
 164 }
 165
 166 static bool sbusInitEx(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig, uint32_t sbusBaudRate)
 167 {
 168     static uint16_t sbusChannelData[SBUS_MAX_CHANNEL];
 169     static sbusFrameData_t sbusFrameData;
 170
 171     rxRuntimeConfig->channelData = sbusChannelData;
 172     rxRuntimeConfig->frameData = &sbusFrameData;
 173
 174     sbusChannelsInit(rxRuntimeConfig);
 175
 176     rxRuntimeConfig->channelCount = SBUS_MAX_CHANNEL;
 177     rxRuntimeConfig->rxRefreshRate = 11000;
 178
 179     rxRuntimeConfig->rcFrameStatusFn = sbusFrameStatus;
 180
 181     const serialPortConfig_t *portConfig = findSerialPortConfig(FUNCTION_RX_SERIAL);
 182     if (!portConfig) {
 183         return false;
 184     }
 185
 186 #ifdef USE_TELEMETRY
 187     bool portShared = telemetryCheckRxPortShared(portConfig);
 188 #else
 189     bool portShared = false;
 190 #endif
 191
 192     serialPort_t *sBusPort = openSerialPort(portConfig->identifier,
 193         FUNCTION_RX_SERIAL,
 194         sbusDataReceive,
 195         &sbusFrameData,
 196         sbusBaudRate,
 197         portShared ? MODE_RXTX : MODE_RX,
 198         SBUS_PORT_OPTIONS |
 199             (rxConfig->serialrx_inverted ? 0 : SERIAL_INVERTED) |
 200             (tristateWithDefaultOffIsActive(rxConfig->halfDuplex) ? SERIAL_BIDIR : 0)
 201         );
 202
 203 #ifdef USE_TELEMETRY
 204     if (portShared) {
 205         telemetrySharedPort = sBusPort;
 206     }
 207 #endif
 208
 209     return sBusPort != NULL;
 210 }
 211
 212 bool sbusInit(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig)
 213 {
 214     return sbusInitEx(rxConfig, rxRuntimeConfig, SBUS_BAUDRATE);
 215 }
 216
 217 bool sbusInitFast(const rxConfig_t *rxConfig, rxRuntimeConfig_t *rxRuntimeConfig)
 218 {
 219     return sbusInitEx(rxConfig, rxRuntimeConfig, SBUS_BAUDRATE_FAST);
 220 }
 221 #endif