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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>
This commit is contained in:
Tobias Schramm 2018-05-19 19:20:24 +02:00
parent 9ef7e0b936
commit 2dd9d37bb3
2 changed files with 36 additions and 5 deletions
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34
Src/control.c
View File

@ -3,6 +3,8 @@
#include "defines.h"
#include "setup.h"
#include "config.h"
#include <stdbool.h>
#include <string.h>
TIM_HandleTypeDef TimHandle;
uint8_t ppm_count = 0;
@ -16,7 +18,13 @@ DMA_HandleTypeDef hdma_i2c2_rx;
DMA_HandleTypeDef hdma_i2c2_tx;
#ifdef CONTROL_PPM
uint16_t ppm_captured_value[PPM_NUM_CHANNELS+1] = {0};
uint16_t ppm_captured_value[PPM_NUM_CHANNELS + 1] = {500, 500};
uint16_t ppm_captured_value_buffer[PPM_NUM_CHANNELS+1] = {500, 500};
uint32_t ppm_timeout = 0;
bool ppm_valid = true;
#define IN_RANGE(x, low, up) (((x) >= (low)) && ((x) <= (up)))
void PPM_ISR_Callback() {
// Dummy loop with 16 bit count wrap around
@ -24,14 +32,32 @@ void PPM_ISR_Callback() {
TIM2->CNT = 0;
if (rc_delay > 3000) {
if (ppm_valid && ppm_count == PPM_NUM_CHANNELS) {
ppm_timeout = 0;
memcpy(ppm_captured_value, ppm_captured_value_buffer, sizeof(ppm_captured_value));
}
ppm_valid = true;
ppm_count = 0;
}
else if (ppm_count < PPM_NUM_CHANNELS){
else if (ppm_count < PPM_NUM_CHANNELS && IN_RANGE(rc_delay, 900, 2100)){
timeout = 0;
ppm_captured_value[ppm_count] = CLAMP(rc_delay, 1000, 2000) - 1000;
ppm_count++;
ppm_captured_value_buffer[ppm_count++] = CLAMP(rc_delay, 1000, 2000) - 1000;
} else {
ppm_valid = false;
}
}
// SysTick executes once each ms
void PPM_SysTick_Callback() {
ppm_timeout++;
// Stop after 500 ms without PPM signal
if(ppm_timeout > 500) {
int i;
for(i = 0; i < PPM_NUM_CHANNELS; i++) {
ppm_captured_value[i] = 500;
}
ppm_timeout = 0;
}
}
void PPM_Init() {

7
Src/stm32f1xx_it.c
View File

@ -158,6 +158,9 @@ void PendSV_Handler(void) {
/**
* @brief This function handles System tick timer.
*/
#ifdef CONTROL_PPM
void PPM_SysTick_Callback(void);
#endif
void SysTick_Handler(void) {
/* USER CODE BEGIN SysTick_IRQn 0 */
@ -165,7 +168,9 @@ void SysTick_Handler(void) {
HAL_IncTick();
HAL_SYSTICK_IRQHandler();
/* USER CODE BEGIN SysTick_IRQn 1 */
#ifdef CONTROL_PPM
PPM_SysTick_Callback();
#endif
/* USER CODE END SysTick_IRQn 1 */
}