Enhance robustness of PPM parsing
Add additional checks to ensure only valid PPM pulse trains are accepted. Add auto-idle feature to ensure vehicle stops if PPM signal is lost. Co-authored-by: Tobias Mädel <t.maedel@alfeld.de>
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@ -3,6 +3,8 @@
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#include "defines.h"
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#include "setup.h"
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#include "config.h"
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#include <stdbool.h>
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#include <string.h>
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TIM_HandleTypeDef TimHandle;
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uint8_t ppm_count = 0;
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@ -16,7 +18,13 @@ DMA_HandleTypeDef hdma_i2c2_rx;
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DMA_HandleTypeDef hdma_i2c2_tx;
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#ifdef CONTROL_PPM
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uint16_t ppm_captured_value[PPM_NUM_CHANNELS+1] = {0};
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uint16_t ppm_captured_value[PPM_NUM_CHANNELS + 1] = {500, 500};
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uint16_t ppm_captured_value_buffer[PPM_NUM_CHANNELS+1] = {500, 500};
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uint32_t ppm_timeout = 0;
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bool ppm_valid = true;
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#define IN_RANGE(x, low, up) (((x) >= (low)) && ((x) <= (up)))
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void PPM_ISR_Callback() {
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// Dummy loop with 16 bit count wrap around
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@ -24,14 +32,32 @@ void PPM_ISR_Callback() {
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TIM2->CNT = 0;
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if (rc_delay > 3000) {
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if (ppm_valid && ppm_count == PPM_NUM_CHANNELS) {
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ppm_timeout = 0;
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memcpy(ppm_captured_value, ppm_captured_value_buffer, sizeof(ppm_captured_value));
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}
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ppm_valid = true;
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ppm_count = 0;
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}
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else if (ppm_count < PPM_NUM_CHANNELS){
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else if (ppm_count < PPM_NUM_CHANNELS && IN_RANGE(rc_delay, 900, 2100)){
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timeout = 0;
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ppm_captured_value[ppm_count] = CLAMP(rc_delay, 1000, 2000) - 1000;
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ppm_count++;
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ppm_captured_value_buffer[ppm_count++] = CLAMP(rc_delay, 1000, 2000) - 1000;
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} else {
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ppm_valid = false;
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}
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}
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// SysTick executes once each ms
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void PPM_SysTick_Callback() {
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ppm_timeout++;
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// Stop after 500 ms without PPM signal
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if(ppm_timeout > 500) {
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int i;
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for(i = 0; i < PPM_NUM_CHANNELS; i++) {
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ppm_captured_value[i] = 500;
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}
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ppm_timeout = 0;
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}
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}
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void PPM_Init() {
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@ -158,6 +158,9 @@ void PendSV_Handler(void) {
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/**
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* @brief This function handles System tick timer.
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*/
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#ifdef CONTROL_PPM
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void PPM_SysTick_Callback(void);
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#endif
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void SysTick_Handler(void) {
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/* USER CODE BEGIN SysTick_IRQn 0 */
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@ -165,7 +168,9 @@ void SysTick_Handler(void) {
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HAL_IncTick();
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HAL_SYSTICK_IRQHandler();
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/* USER CODE BEGIN SysTick_IRQn 1 */
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#ifdef CONTROL_PPM
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PPM_SysTick_Callback();
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#endif
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/* USER CODE END SysTick_IRQn 1 */
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}
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