I'm writing library for HC-SR-4 (Ranging Module). To start measurement I have to:
1) send 10 us high signal to TRIGGER and than
2) measure duration of high signal on ECHO
To get 10 us duration I use one of basic timers with enabled interruption.
When I try to send signal TRIGGER for the first time I get strange early interruption. On the picture, you can see measurement performed by logical analyzer after pressing the button (which also sets high level on TRIGGER and starts timer):
Next press:
I can ignore this first interruption since after it timer works correctly. But to make library work I use two timers instead of one. For now it is not so bad but it is improper approach and I would like to understand why this happens.
Answering Clive:
Timer settings
/* TIM7 init function */
void MX_TIM7_Init(void)
{
TIM_MasterConfigTypeDef sMasterConfig = {0};
htim7.Instance = TIM7;
htim7.Init.Prescaler = 79;
htim7.Init.CounterMode = TIM_COUNTERMODE_UP;
htim7.Init.Period = 9;
htim7.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
if (HAL_TIM_Base_Init(&htim7) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_UPDATE;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim7, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
}Interruption
/**
* @brief This function handles TIM7 global interrupt.
*/
void TIM7_IRQHandler(void)
{
/* USER CODE BEGIN TIM7_IRQn 0 */
/* USER CODE END TIM7_IRQn 0 */
HAL_TIM_IRQHandler(&htim7);
/* USER CODE BEGIN TIM7_IRQn 1 */
HAL_TIM_Base_Stop_IT(&htim7);
HAL_GPIO_TogglePin(TRIG_PORT, TRIG);
/* USER CODE END TIM7_IRQn 1 */
}Button
void EXTI0_IRQHandler(void)
{
/* USER CODE BEGIN EXTI0_IRQn 0 */
/* USER CODE END EXTI0_IRQn 0 */
HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_0);
/* USER CODE BEGIN EXTI0_IRQn 1 */
HAL_GPIO_TogglePin(GPIOB, GPIO_PIN_2);
htim7.Instance->CNT = 0;
HAL_TIM_Base_Start_IT(&htim7);
HAL_GPIO_WritePin(TRIG_PORT, TRIG, 1);
/* USER CODE END EXTI0_IRQn 1 */
}Clock configuration
Thank you,
Khetag
