Using TIMER in Encoder Mode with interrupts on value change

Posted on June 19, 2018 at 11:55

Hi all,

I'm quite new to the embedded stm32 environment so if I'm asking something stupid please forgive me.

First of all, my setup. 

I'm using a NUCLEO-32bit with STM32L432KC, and we need to test some performances on encoders because we have some problems. 

One of these tests is the one in which I'm stuck. 

Basically I want to use one of the available TIMx  (TIM2) in Encoder Mode with interrupts, and I've successfully managed to do let's say 80% of the work. The only part that I'm stuck with is the interrupt part: I want to fire an interrupt each time the CNT value changes, and also know the direction of the change (i.e. if my encoder rotates CW, increase a variable, if it rotates ACW i want the variable to decrement).

Actually the interrupt fires regularly also when the CNT value of encoder does not changes, so I do not know what I'm doing wrong. And I also experience a strange behaviour of the encoder: also when it is not moved, sometimes the CNT value decrements itself until 0. 

Here my actual code:

/* TIM2 init function */

static void MX_TIM2_Init(void)

{

TIM_Encoder_InitTypeDef sConfig;

TIM_MasterConfigTypeDef sMasterConfig;

htim2.Instance = TIM2;

htim2.Init.Prescaler = 0;

htim2.Init.CounterMode = TIM_COUNTERMODE_UP;

htim2.Init.Period = 200;

htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;

htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

sConfig.EncoderMode = TIM_ENCODERMODE_TI12;

sConfig.IC1Polarity = TIM_ICPOLARITY_RISING;

sConfig.IC1Selection = TIM_ICSELECTION_DIRECTTI;

sConfig.IC1Prescaler = TIM_ICPSC_DIV1;

sConfig.IC1Filter = 15;

sConfig.IC2Polarity = TIM_ICPOLARITY_RISING;

sConfig.IC2Selection = TIM_ICSELECTION_DIRECTTI;

sConfig.IC2Prescaler = TIM_ICPSC_DIV1;

sConfig.IC2Filter = 15;

if (HAL_TIM_Encoder_Init(&htim2, &sConfig) != HAL_OK)

{

_Error_Handler(__FILE__, __LINE__);

}

sMasterConfig.MasterOutputTrigger = TIM_TRGO_UPDATE;

sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;

if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)

{

_Error_Handler(__FILE__, __LINE__);

}

}

/* MAIN */

int main(void)

{

/* USER CODE BEGIN 1 */

/* USER CODE END 1 */

/* MCU Configuration----------------------------------------------------------*/

/* Reset of all peripherals, Initializes the Flash interface and the Systick. */

HAL_Init();

/* USER CODE BEGIN Init */

/* USER CODE END Init */

/* Configure the system clock */

SystemClock_Config();

/* USER CODE BEGIN SysInit */

/* USER CODE END SysInit */

/* Initialize all configured peripherals */

MX_GPIO_Init();

MX_TIM2_Init();

MX_USART2_UART_Init();

/* USER CODE BEGIN 2 */

/* USER CODE END 2 */

HAL_TIM_Encoder_Start_IT(&htim2,htim2.Channel);

/* Infinite loop */

/* USER CODE BEGIN WHILE */

while (1)

{

/* USER CODE END WHILE */

/* USER CODE BEGIN 3 */

}

/* USER CODE END 3 */

}

/* the last part is the IRQ handler: */

void TIM2_IRQHandler(void)

{

/* USER CODE BEGIN TIM2_IRQn 0 */

char asd[50];

sprintf(asd,'%d\n',htim2.Instance->CNT);

HAL_UART_Transmit(&huart2,(uint8_t *)asd,sizeof(asd),20);

/* USER CODE END TIM2_IRQn 0 */

HAL_TIM_IRQHandler(&htim2);

/* USER CODE BEGIN TIM2_IRQn 1 */

/* USER CODE END TIM2_IRQn 1 */

}

The part regarding init functions has been automatically generated by CubeMX.

has Anyone an Idea on what's the problem?

Thanks!

#quadrature-encoder #nucleo-l432kc #timer-interrupts #st-cube