ADD: ppm input

Src/control.c

@@ -0,0 +1,52 @@
+
+#include "stm32f1xx_hal.h"
+#include "defines.h"
+#include "setup.h"
+#include "config.h"
+
+TIM_HandleTypeDef TimHandle;
+uint16_t ppm_captured_value[PPM_NUM_CHANNELS+1] = {0};
+uint8_t ppm_count = 0;
+uint32_t timeout = 0;
+
+void PPM_ISR_Callback() {
+  // Dummy loop with 16 bit count wrap around
+  uint16_t rc_delay = TIM2->CNT;
+  TIM2->CNT = 0;
+
+  HAL_TIM_Base_Stop(&TimHandle);
+  __HAL_RCC_TIM2_CLK_DISABLE();
+
+  if (rc_delay > 3000) {
+    ppm_count = 0;
+  }
+  else if (ppm_count < PPM_NUM_CHANNELS){
+    timeout = 0;
+    ppm_captured_value[ppm_count] = CLAMP(rc_delay, 1000, 2000) - 1000;
+    ppm_count++;
+  }
+  __HAL_RCC_TIM2_CLK_ENABLE();
+  HAL_TIM_Base_Start(&TimHandle);
+}
+
+void PPM_Init() {
+  GPIO_InitTypeDef GPIO_InitStruct;
+  /*Configure GPIO pin : PA3 */
+  GPIO_InitStruct.Pin = GPIO_PIN_3;
+  GPIO_InitStruct.Mode = GPIO_MODE_IT_FALLING;
+  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
+  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
+  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
+
+  __HAL_RCC_TIM2_CLK_ENABLE();
+  TimHandle.Instance = TIM2;
+  TimHandle.Init.Period = UINT16_MAX;
+  TimHandle.Init.Prescaler = (SystemCoreClock/DELAY_TIM_FREQUENCY_US)-1;;
+  TimHandle.Init.ClockDivision = 0;
+  TimHandle.Init.CounterMode = TIM_COUNTERMODE_UP;
+  HAL_TIM_Base_Init(&TimHandle);
+
+  /* EXTI interrupt init*/
+  HAL_NVIC_SetPriority(EXTI3_IRQn, 0, 0);
+  HAL_NVIC_EnableIRQ(EXTI3_IRQn);
+}