Timer Encoder Function STM32F091 Nucleo Board

[Nicholas Yunker_2]

I am attempting to use a rotary encoder (Bourns PEC11R-4215F-S0024) with an STM32F091 Nucleo board.  I would like to have it count a consist number of "counts" for every "click" of the encoder.

Hardware Setup: Pin A is connected to PA0, Pin B is connected to PA1 and Pin C (common) is connected to the ground on the nucleo board.  This is all done with jumper wires.

CubeMX setup: Clock Tree set to have a max frequency of 48MHz using the internal clock.  PA1 and PA2 are set to have Pull-Up Resistors, TIM2 is set to Combined Channels = Encoder Mode.  All the TIM2 parameters are left at default except for Encoder Mode = Encoder Mode TI1 and TI2, Polarity of both are set to Falling Edge.

Here is my main.c code:

/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2023 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
*/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
TIM_HandleTypeDef htim2;

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM2_Init(void);
/* USER CODE BEGIN PFP */
uint32_t counter = 0;
/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
* @brief The application entry point.
* @retval int
*/
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();
/* USER CODE BEGIN 2 */
HAL_TIM_Encoder_Start_IT(&htim2, TIM_CHANNEL_ALL);
/* USER CODE END 2 */

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

/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}

/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI48;
RCC_OscInitStruct.HSI48State = RCC_HSI48_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI48;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL2;
RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}

/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;

if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK)
{
Error_Handler();
}
}

/**
* @brief TIM2 Initialization Function
* @PAram None
* @retval None
*/
static void MX_TIM2_Init(void)
{

/* USER CODE BEGIN TIM2_Init 0 */

/* USER CODE END TIM2_Init 0 */

TIM_Encoder_InitTypeDef sConfig = {0};
TIM_MasterConfigTypeDef sMasterConfig = {0};

/* USER CODE BEGIN TIM2_Init 1 */

/* USER CODE END TIM2_Init 1 */
htim2.Instance = TIM2;
htim2.Init.Prescaler = 0;
htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
htim2.Init.Period = 4294967295;
htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
sConfig.EncoderMode = TIM_ENCODERMODE_TI12;
sConfig.IC1Polarity = TIM_ICPOLARITY_FALLING;
sConfig.IC1Selection = TIM_ICSELECTION_DIRECTTI;
sConfig.IC1Prescaler = TIM_ICPSC_DIV1;
sConfig.IC1Filter = 0;
sConfig.IC2Polarity = TIM_ICPOLARITY_FALLING;
sConfig.IC2Selection = TIM_ICSELECTION_DIRECTTI;
sConfig.IC2Prescaler = TIM_ICPSC_DIV1;
sConfig.IC2Filter = 0;
if (HAL_TIM_Encoder_Init(&htim2, &sConfig) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN TIM2_Init 2 */

/* USER CODE END TIM2_Init 2 */

}

/**
* @brief GPIO Initialization Function
* @PAram None
* @retval None
*/
static void MX_GPIO_Init(void)
{

/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOA_CLK_ENABLE();

}

/* USER CODE BEGIN 4 */
void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *htim)
{
counter = __HAL_TIM_GET_COUNTER(htim);
}
/* USER CODE END 4 */

/**
* @brief This function is executed in case of error occurrence.
* @retval None
*/
void Error_Handler(void)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
__disable_irq();
while (1)
{
}
/* USER CODE END Error_Handler_Debug */
}

#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @PAram file: pointer to the source file name
* @PAram line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t *file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

I have confirmed with an oscilliscope that my encoder signal is clean, there is no noise or glitches.  I would expect from these settings my counter value would increase/decrease by 4 each click of the encoder (depending on direction of the turn).  However, I am getting randome numbers of increases and decreases.  The direction of the count (up vs. down) seems to be accurate but the magnitude of the change is different each time.

Viewing the TIM2 Peripheral in Keil while I turn the encoder I see that the CNT register is accuratly increaseing/decreasing by 4 on each click, the CCR1 Register does not perfectly follow the CNT register...sometimes it does, sometimes it doesn't.  Also, the value of my variable "counter" that is being set inside the capture callback function is not following the CNT register like it should be.

During testing one thing I have noticed is that the CaptureCallback function is being entered considerably more often than it the CNT value is changing.  For instance, the value of CNT may increase by 4 but the CaptureCallback function is entered 5 times over when it should be entered once.  My understanding is that this CaptureCallback function should only be entered once when the CNT value changes, is this not the case?  I have found that if i set a breakpoint inside the CaptureCallback function and then manually run the program again after it breaks it works perfectly every time.  Do I need a delay within the CaptureCallback function to make this work right?