src/main/rx/sbus_channels.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 #ifdef USE_SERIAL_RX
  25
  26 #include "common/utils.h"
  27 #include "common/maths.h"
  28
  29 #include "rx/sbus_channels.h"
  30
  31
  32 #define SBUS_DIGITAL_CHANNEL_MIN 173
  33 #define SBUS_DIGITAL_CHANNEL_MAX 1812
  34
  35 STATIC_ASSERT(SBUS_FRAME_SIZE == sizeof(sbusFrame_t), SBUS_FRAME_SIZE_doesnt_match_sbusFrame_t);
  36
  37 uint8_t sbusChannelsDecode(rxRuntimeConfig_t *rxRuntimeConfig, const sbusChannels_t *channels)
  38 {
  39     uint16_t *sbusChannelData = rxRuntimeConfig->channelData;
  40     sbusChannelData[0] = channels->chan0;
  41     sbusChannelData[1] = channels->chan1;
  42     sbusChannelData[2] = channels->chan2;
  43     sbusChannelData[3] = channels->chan3;
  44     sbusChannelData[4] = channels->chan4;
  45     sbusChannelData[5] = channels->chan5;
  46     sbusChannelData[6] = channels->chan6;
  47     sbusChannelData[7] = channels->chan7;
  48     sbusChannelData[8] = channels->chan8;
  49     sbusChannelData[9] = channels->chan9;
  50     sbusChannelData[10] = channels->chan10;
  51     sbusChannelData[11] = channels->chan11;
  52     sbusChannelData[12] = channels->chan12;
  53     sbusChannelData[13] = channels->chan13;
  54     sbusChannelData[14] = channels->chan14;
  55     sbusChannelData[15] = channels->chan15;
  56
  57     if (channels->flags & SBUS_FLAG_CHANNEL_17) {
  58         sbusChannelData[16] = SBUS_DIGITAL_CHANNEL_MAX;
  59     } else {
  60         sbusChannelData[16] = SBUS_DIGITAL_CHANNEL_MIN;
  61     }
  62
  63     if (channels->flags & SBUS_FLAG_CHANNEL_18) {
  64         sbusChannelData[17] = SBUS_DIGITAL_CHANNEL_MAX;
  65     } else {
  66         sbusChannelData[17] = SBUS_DIGITAL_CHANNEL_MIN;
  67     }
  68
  69     if (channels->flags & SBUS_FLAG_FAILSAFE_ACTIVE) {
  70         // internal failsafe enabled and rx failsafe flag set
  71         // RX *should* still be sending valid channel data, so use it.
  72         return RX_FRAME_COMPLETE | RX_FRAME_FAILSAFE;
  73     }
  74
  75     if (channels->flags & SBUS_FLAG_SIGNAL_LOSS) {
  76         // The received data is a repeat of the last valid data so can be considered complete.
  77         return RX_FRAME_COMPLETE | RX_FRAME_DROPPED;
  78     }
  79
  80     return RX_FRAME_COMPLETE;
  81 }
  82
  83 uint16_t sbusDecodeChannelValue(uint16_t sbusValue, bool safeValuesOnly)
  84 {
  85     // Linear fitting values read from OpenTX-ppmus and comparing with values received by X4R
  86     // http://www.wolframalpha.com/input/?i=linear+fit+%7B173%2C+988%7D%2C+%7B1812%2C+2012%7D%2C+%7B993%2C+1500%7D
  87     if (safeValuesOnly) {
  88         // Clip channel values to more or less safe values (988 .. 2012)
  89         return (5 * constrain(sbusValue, SBUS_DIGITAL_CHANNEL_MIN, SBUS_DIGITAL_CHANNEL_MAX) / 8) + 880;
  90     }
  91     else {
  92         // Use full range of values (11 bit, channel values in range 880 .. 2159)
  93         return (5 * constrain(sbusValue, 0, 2047) / 8) + 880;
  94     }
  95 }
  96
  97 uint16_t sbusEncodeChannelValue(uint16_t rcValue)
  98 {
  99     return constrain((((int)rcValue - 880) * 8 + 4) / 5, SBUS_DIGITAL_CHANNEL_MIN, SBUS_DIGITAL_CHANNEL_MAX);
 100 }
 101
 102 static uint16_t sbusChannelsReadRawRC(const rxRuntimeConfig_t *rxRuntimeConfig, uint8_t chan)
 103 {
 104     return sbusDecodeChannelValue(rxRuntimeConfig->channelData[chan], false);
 105 }
 106
 107 void sbusChannelsInit(rxRuntimeConfig_t *rxRuntimeConfig)
 108 {
 109     rxRuntimeConfig->rcReadRawFn = sbusChannelsReadRawRC;
 110     for (int b = 0; b < SBUS_MAX_CHANNEL; b++) {
 111         rxRuntimeConfig->channelData[b] = (16 * PWM_RANGE_MIDDLE) / 10 - 1408;
 112     }
 113 }
 114 #endif