/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "stdio.h"
#include "string.h"

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
#define TRIG_PIN GPIO_PIN_10
#define TRIG_PORT GPIOA
/* USER CODE END PD */

/* Private variables ---------------------------------------------------------*/
TIM_HandleTypeDef htim1;

UART_HandleTypeDef huart1;
DMA_HandleTypeDef hdma_usart1_tx;

/* USER CODE BEGIN PV */
uint32_t IC_Val1 = 0;
uint32_t IC_Val2 = 0;
uint32_t Difference = 0;
uint8_t Is_First_Captured = 0;  // is the first value captured ?
uint8_t Distance  = 0;
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_DMA_Init(void);
static void MX_TIM1_Init(void);
static void MX_USART1_UART_Init(void);

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim)
{
    if (htim->Channel == HAL_TIM_ACTIVE_CHANNEL_2)  // if the interrupt source is channel1
    {
        if (Is_First_Captured==0) // if the first value is not captured
        {
            IC_Val1 = HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_2); // read the first value
            Is_First_Captured = 1;  // set the first captured as true
            // Now change the polarity to falling edge
            __HAL_TIM_SET_CAPTUREPOLARITY(htim, TIM_CHANNEL_2, TIM_INPUTCHANNELPOLARITY_FALLING);
        }

        else if (Is_First_Captured==1)   // if the first is already captured
        {
            IC_Val2 = HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_2);  // read second value
            __HAL_TIM_SET_COUNTER(htim, 0);  // reset the counter

            if (IC_Val2 > IC_Val1)
            {
                Difference = IC_Val2-IC_Val1;
            }

            else if (IC_Val1 > IC_Val2)
            {
                Difference = (0xffff - IC_Val1) + IC_Val2;
            }

            Distance = Difference * (0.034/2);
            Is_First_Captured = 0; // set it back to false

            // set polarity to rising edge
            __HAL_TIM_SET_CAPTUREPOLARITY(htim, TIM_CHANNEL_2, TIM_INPUTCHANNELPOLARITY_RISING);
            __HAL_TIM_DISABLE_IT(&htim1, TIM_IT_CC2);
        }
    }
}

void HCSR04_Read (void)
{
    HAL_GPIO_WritePin(TRIG_PORT, TRIG_PIN, GPIO_PIN_SET);  // pull the TRIG pin HIGH
    HAL_Delay(10);  // wait for 10 us
    HAL_GPIO_WritePin(TRIG_PORT, TRIG_PIN, GPIO_PIN_RESET);  // pull the TRIG pin low

    __HAL_TIM_ENABLE_IT(&htim1, TIM_IT_CC2);
}
/* USER CODE END 0 */

int main(void)
{
  /* USER CODE BEGIN 1 */
 char MSG[40];
  /* USER CODE END 1 */

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_DMA_Init();
  MX_TIM1_Init();
  MX_USART1_UART_Init();
  
  /* USER CODE BEGIN 2 */
  HAL_TIM_IC_Start_IT(&htim1, TIM_CHANNEL_2);
  /* USER CODE END 2 */

  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
      HCSR04_Read();

      sprintf(MSG,"Distance : %d cm\n\r",Distance);
      HAL_UART_Transmit(&huart1,(uint8_t*)MSG, strlen(MSG),100);
      HAL_Delay(500);
  }
  /* USER CODE END 3 */
}