src/main/drivers/rx_pwm.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
  21 #include <platform.h>
  22
  23 #if defined(USE_RX_PPM)
  24
  25 #include "build/build_config.h"
  26 #include "build/debug.h"
  27
  28 #include "common/utils.h"
  29
  30 #include "drivers/time.h"
  31
  32 #include "drivers/nvic.h"
  33 #include "drivers/io.h"
  34 #include "timer.h"
  35
  36 #include "pwm_output.h"
  37 #include "pwm_mapping.h"
  38
  39 #include "rx_pwm.h"
  40
  41 #define PPM_CAPTURE_COUNT       16
  42 #define INPUT_FILTER_TICKS      10
  43 #define PPM_TIMER_PERIOD        0x10000
  44
  45 void pwmICConfig(TIM_TypeDef *tim, uint8_t channel, uint16_t polarity);
  46
  47 static uint16_t captures[PPM_CAPTURE_COUNT];
  48
  49 static uint8_t ppmFrameCount = 0;
  50 static uint8_t lastPPMFrameCount = 0;
  51 static uint8_t ppmCountDivisor = 1;
  52
  53 typedef struct ppmDevice_s {
  54     uint8_t  pulseIndex;
  55     uint32_t currentCapture;
  56     uint32_t currentTime;
  57     uint32_t deltaTime;
  58     uint32_t captures[PPM_CAPTURE_COUNT];
  59     uint32_t largeCounter;
  60     int8_t   numChannels;
  61     int8_t   numChannelsPrevFrame;
  62     uint8_t  stableFramesSeenCount;
  63
  64     bool     tracking;
  65     bool     overflowed;
  66 } ppmDevice_t;
  67
  68 ppmDevice_t ppmDev;
  69
  70 #define PPM_IN_MIN_SYNC_PULSE_US            2700    // microseconds
  71 #define PPM_IN_MIN_CHANNEL_PULSE_US         750     // microseconds
  72 #define PPM_IN_MAX_CHANNEL_PULSE_US         2250    // microseconds
  73 #define PPM_STABLE_FRAMES_REQUIRED_COUNT    25
  74 #define PPM_IN_MIN_NUM_CHANNELS             4
  75 #define PPM_IN_MAX_NUM_CHANNELS             PPM_CAPTURE_COUNT
  76
  77 bool isPPMDataBeingReceived(void)
  78 {
  79     return (ppmFrameCount != lastPPMFrameCount);
  80 }
  81
  82 void resetPPMDataReceivedState(void)
  83 {
  84     lastPPMFrameCount = ppmFrameCount;
  85 }
  86
  87 #define MIN_CHANNELS_BEFORE_PPM_FRAME_CONSIDERED_VALID 4
  88
  89 static void ppmInit(void)
  90 {
  91     ppmDev.pulseIndex   = 0;
  92     ppmDev.currentCapture = 0;
  93     ppmDev.currentTime  = 0;
  94     ppmDev.deltaTime    = 0;
  95     ppmDev.largeCounter = 0;
  96     ppmDev.numChannels  = -1;
  97     ppmDev.numChannelsPrevFrame = -1;
  98     ppmDev.stableFramesSeenCount = 0;
  99     ppmDev.tracking     = false;
 100     ppmDev.overflowed   = false;
 101 }
 102
 103 static void ppmOverflowCallback(struct TCH_s * tch, uint32_t capture)
 104 {
 105     UNUSED(tch);
 106
 107     ppmDev.largeCounter += capture + 1;
 108     if (capture == PPM_TIMER_PERIOD - 1) {
 109         ppmDev.overflowed = true;
 110     }
 111 }
 112
 113 static void ppmEdgeCallback(struct TCH_s * tch, uint32_t capture)
 114 {
 115     UNUSED(tch);
 116
 117     int32_t i;
 118
 119     uint32_t previousTime = ppmDev.currentTime;
 120     uint32_t previousCapture = ppmDev.currentCapture;
 121
 122     /* Grab the new count */
 123     uint32_t currentTime = capture;
 124
 125     /* Convert to 32-bit timer result */
 126     currentTime += ppmDev.largeCounter;
 127
 128     if (capture < previousCapture) {
 129         if (ppmDev.overflowed) {
 130             currentTime += PPM_TIMER_PERIOD;
 131         }
 132     }
 133
 134     // Divide to match output protocol
 135     currentTime = currentTime / ppmCountDivisor;
 136
 137     /* Capture computation */
 138     if (currentTime > previousTime) {
 139         ppmDev.deltaTime    = currentTime - (previousTime + (ppmDev.overflowed ? (PPM_TIMER_PERIOD / ppmCountDivisor) : 0));
 140     } else {
 141         ppmDev.deltaTime    = (PPM_TIMER_PERIOD / ppmCountDivisor) + currentTime - previousTime;
 142     }
 143
 144     ppmDev.overflowed = false;
 145
 146
 147     /* Store the current measurement */
 148     ppmDev.currentTime = currentTime;
 149     ppmDev.currentCapture = capture;
 150
 151 #if 0
 152     static uint32_t deltaTimes[20];
 153     static uint8_t deltaIndex = 0;
 154
 155     deltaIndex = (deltaIndex + 1) % 20;
 156     deltaTimes[deltaIndex] = ppmDev.deltaTime;
 157     UNUSED(deltaTimes);
 158 #endif
 159
 160
 161 #if 0
 162     static uint32_t captureTimes[20];
 163     static uint8_t captureIndex = 0;
 164
 165     captureIndex = (captureIndex + 1) % 20;
 166     captureTimes[captureIndex] = capture;
 167     UNUSED(captureTimes);
 168 #endif
 169
 170     /* Sync pulse detection */
 171     if (ppmDev.deltaTime > PPM_IN_MIN_SYNC_PULSE_US) {
 172         if (ppmDev.pulseIndex == ppmDev.numChannelsPrevFrame
 173             && ppmDev.pulseIndex >= PPM_IN_MIN_NUM_CHANNELS
 174             && ppmDev.pulseIndex <= PPM_IN_MAX_NUM_CHANNELS) {
 175             /* If we see n simultaneous frames of the same
 176                number of channels we save it as our frame size */
 177             if (ppmDev.stableFramesSeenCount < PPM_STABLE_FRAMES_REQUIRED_COUNT) {
 178                 ppmDev.stableFramesSeenCount++;
 179             } else {
 180                 ppmDev.numChannels = ppmDev.pulseIndex;
 181             }
 182         } else {
 183             ppmDev.stableFramesSeenCount = 0;
 184         }
 185
 186         /* Check if the last frame was well formed */
 187         if (ppmDev.pulseIndex == ppmDev.numChannels && ppmDev.tracking) {
 188             /* The last frame was well formed */
 189             for (i = 0; i < ppmDev.numChannels; i++) {
 190                 captures[i] = ppmDev.captures[i];
 191             }
 192             for (i = ppmDev.numChannels; i < PPM_IN_MAX_NUM_CHANNELS; i++) {
 193                 captures[i] = PPM_RCVR_TIMEOUT;
 194             }
 195             ppmFrameCount++;
 196         }
 197
 198         ppmDev.tracking   = true;
 199         ppmDev.numChannelsPrevFrame = ppmDev.pulseIndex;
 200         ppmDev.pulseIndex = 0;
 201
 202         /* We rely on the supervisor to set captureValue to invalid
 203            if no valid frame is found otherwise we ride over it */
 204     } else if (ppmDev.tracking) {
 205         /* Valid pulse duration 0.75 to 2.5 ms*/
 206         if (ppmDev.deltaTime > PPM_IN_MIN_CHANNEL_PULSE_US
 207             && ppmDev.deltaTime < PPM_IN_MAX_CHANNEL_PULSE_US
 208             && ppmDev.pulseIndex < PPM_IN_MAX_NUM_CHANNELS) {
 209             ppmDev.captures[ppmDev.pulseIndex] = ppmDev.deltaTime;
 210             ppmDev.pulseIndex++;
 211         } else {
 212             /* Not a valid pulse duration */
 213             ppmDev.tracking = false;
 214             for (i = 0; i < PPM_CAPTURE_COUNT; i++) {
 215                 ppmDev.captures[i] = PPM_RCVR_TIMEOUT;
 216             }
 217         }
 218     }
 219 }
 220
 221 bool ppmInConfig(const timerHardware_t *timerHardwarePtr)
 222 {
 223     static timerCallbacks_t callbacks;
 224     TCH_t * tch = timerGetTCH(timerHardwarePtr);
 225     if (tch == NULL) {
 226         return false;
 227     }
 228
 229     ppmInit();
 230
 231     IO_t io = IOGetByTag(timerHardwarePtr->tag);
 232     IOInit(io, OWNER_PPMINPUT, RESOURCE_INPUT, 0);
 233     IOConfigGPIOAF(io, timerHardwarePtr->ioMode, timerHardwarePtr->alternateFunction);
 234
 235     timerConfigure(tch, (uint16_t)PPM_TIMER_PERIOD, PWM_TIMER_HZ);
 236     timerChInitCallbacks(&callbacks, (void*)&ppmDev, &ppmEdgeCallback, &ppmOverflowCallback);
 237     timerChConfigCallbacks(tch, &callbacks);
 238     timerChConfigIC(tch, true, INPUT_FILTER_TICKS);
 239     timerChCaptureEnable(tch);
 240
 241     return true;
 242 }
 243
 244 uint16_t ppmRead(uint8_t channel)
 245 {
 246     return captures[channel];
 247 }
 248 #endif