STM32H742 - Timer output is not exceeding 680 kHz on the GPIO

eogos · ‎2025-09-24

Post edited by ST moderator to be inline with the community rules especially with the code sharing. In next time please use </> button to paste your code. Please read this post: How to insert source code

Issue:
I'm using STM32H742, and I'm currently using timer3 (TIM3) to give a signal over CLK 50MHz to PC4 pins.
However, when the code is written as follows, the period is not increasing beyond 680 kHz.
The pin frequency speed is also set to VERY_HIGH.

The system clock is set to 480 MHz, and the AHB and APB Timer CLOCK are also set to a maximum of 240 MHz.

When you adjust the prescaler, period, and pulse values of the Timer
It has been confirmed that the period increases gradually up to prescaler = 0, period = 99, and pulse = 51, but as the period decreases gradually, the cycle change of PC4 is not large and the value decreases.
In this case, prescaler = 0, period = 99, pulse = 51, one cycle of PC4 is 680 kHz.

And when I toggle PC4 from the callback function, it doesn't come out as a cycle of TIMER, it comes out as a double-decrease cycle. I wonder why this is also the case.

CODE:

/* USER CODE BEGIN Header */

/**

******************************************************************************

* @file : main.c

* @brief : Main program body

******************************************************************************

* @attention

*

* Copyright (c) 2025 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 htim3;



/* USER CODE BEGIN PV */



/* USER CODE END PV */



/* Private function prototypes -----------------------------------------------*/

void SystemClock_Config(void);

void PeriphCommonClock_Config(void);

static void MPU_Config(void);

static void MX_GPIO_Init(void);

static void MX_TIM3_Init(void);

/* USER CODE BEGIN PFP */



/* USER CODE END PFP */



/* Private user code ---------------------------------------------------------*/

/* USER CODE BEGIN 0 */

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)

{

if (htim->Instance == TIM3) /* 1s */

{

HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_4);

}

}

/* USER CODE END 0 */



/**

* @brief The application entry point.

* @retval int

*/

int main(void)

{



/* USER CODE BEGIN 1 */

/* USER CODE END 1 */



/* MPU Configuration--------------------------------------------------------*/

MPU_Config();



/* 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();



/* Configure the peripherals common clocks */

PeriphCommonClock_Config();



/* USER CODE BEGIN SysInit */



/* USER CODE END SysInit */



/* Initialize all configured peripherals */

MX_GPIO_Init();

MX_TIM3_Init();

/* USER CODE BEGIN 2 */

HAL_TIM_Base_Start_IT(&htim3);

//HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_2);

/* USER CODE END 2 */



/* Infinite loop */

/* USER CODE BEGIN WHILE */

while (1) {

//GPIOC->ODR = GPIO_PIN_4;

//GPIOC->ODR = 0;

//AL_GPIO_TogglePin(GPIOC, GPIO_PIN_4);

//HAL_Delay(10);

/*

htim3.Instance->CCR4 = value; // duty 변경

HAL_Delay(10); // 10ms 대기

value++;

if(value > 999) // 최대치까지 갔으면 다시 0으로 시작

value = 0;

*/

/* 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};



/** Supply configuration update enable

*/

HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);



/** Configure the main internal regulator output voltage

*/

__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE0);



while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}



/** Initializes the RCC Oscillators according to the specified parameters

* in the RCC_OscInitTypeDef structure.

*/

RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;

RCC_OscInitStruct.HSEState = RCC_HSE_ON;

RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;

RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;

RCC_OscInitStruct.PLL.PLLM = 2;

RCC_OscInitStruct.PLL.PLLN = 80;

RCC_OscInitStruct.PLL.PLLP = 2;

RCC_OscInitStruct.PLL.PLLQ = 8;

RCC_OscInitStruct.PLL.PLLR = 2;

RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_3;

RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;

RCC_OscInitStruct.PLL.PLLFRACN = 0;

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_CLOCKTYPE_PCLK2

|RCC_CLOCKTYPE_D3PCLK1|RCC_CLOCKTYPE_D1PCLK1;

RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;

RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;

RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV2;

RCC_ClkInitStruct.APB3CLKDivider = RCC_APB3_DIV2;

RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV2;

RCC_ClkInitStruct.APB2CLKDivider = RCC_APB2_DIV2;

RCC_ClkInitStruct.APB4CLKDivider = RCC_APB4_DIV2;



if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)

{

Error_Handler();

}

}



/**

* @brief Peripherals Common Clock Configuration

* @retval None

*/

void PeriphCommonClock_Config(void)

{

RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};



/** Initializes the peripherals clock

*/

PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_TIM;

PeriphClkInitStruct.TIMPresSelection = RCC_TIMPRES_ACTIVATED;



if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)

{

Error_Handler();

}

}



/**

* @brief TIM3 Initialization Function

*  None

* @retval None

*/

static void MX_TIM3_Init(void)

{



/* USER CODE BEGIN TIM3_Init 0 */



/* USER CODE END TIM3_Init 0 */



TIM_ClockConfigTypeDef sClockSourceConfig = {0};

TIM_MasterConfigTypeDef sMasterConfig = {0};

TIM_OC_InitTypeDef sConfigOC = {0};



/* USER CODE BEGIN TIM3_Init 1 */



/* USER CODE END TIM3_Init 1 */

htim3.Instance = TIM3;

htim3.Init.Prescaler = 0;

htim3.Init.CounterMode = TIM_COUNTERMODE_UP;

htim3.Init.Period = 100-1;

htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;

htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

if (HAL_TIM_Base_Init(&htim3) != HAL_OK)

{

Error_Handler();

}

sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;

if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)

{

Error_Handler();

}

if (HAL_TIM_PWM_Init(&htim3) != HAL_OK)

{

Error_Handler();

}

sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;

sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;

if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)

{

Error_Handler();

}

sConfigOC.OCMode = TIM_OCMODE_PWM1;

sConfigOC.Pulse = 51;

sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;

sConfigOC.OCFastMode = TIM_OCFAST_ENABLE;

if (HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_2) != HAL_OK)

{

Error_Handler();

}

/* USER CODE BEGIN TIM3_Init 2 */



/* USER CODE END TIM3_Init 2 */

HAL_TIM_MspPostInit(&htim3);



}



/**

* @brief GPIO Initialization Function

*  None

* @retval None

*/

static void MX_GPIO_Init(void)

{

GPIO_InitTypeDef GPIO_InitStruct = {0};

/* USER CODE BEGIN MX_GPIO_Init_1 */



/* USER CODE END MX_GPIO_Init_1 */



/* GPIO Ports Clock Enable */

__HAL_RCC_GPIOH_CLK_ENABLE();

__HAL_RCC_GPIOC_CLK_ENABLE();



/*Configure GPIO pin Output Level */

HAL_GPIO_WritePin(GPIOC, GPIO_PIN_4, GPIO_PIN_RESET);



/*Configure GPIO pin : PC4 */

GPIO_InitStruct.Pin = GPIO_PIN_4;

GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;

GPIO_InitStruct.Pull = GPIO_NOPULL;

GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;

HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);



/* USER CODE BEGIN MX_GPIO_Init_2 */



/* USER CODE END MX_GPIO_Init_2 */

}



/* USER CODE BEGIN 4 */



/* USER CODE END 4 */



/* MPU Configuration */



void MPU_Config(void)

{

MPU_Region_InitTypeDef MPU_InitStruct = {0};



/* Disables the MPU */

HAL_MPU_Disable();



/** Initializes and configures the Region and the memory to be protected

*/

MPU_InitStruct.Enable = MPU_REGION_ENABLE;

MPU_InitStruct.Number = MPU_REGION_NUMBER0;

MPU_InitStruct.BaseAddress = 0x0;

MPU_InitStruct.Size = MPU_REGION_SIZE_4GB;

MPU_InitStruct.SubRegionDisable = 0x87;

MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;

MPU_InitStruct.AccessPermission = MPU_REGION_NO_ACCESS;

MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;

MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;

MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;

MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;



HAL_MPU_ConfigRegion(&MPU_InitStruct);

/* Enables the MPU */

HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);



}



/**

* @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.

*  file: pointer to the source file name

*  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 */

Saket_Om · ‎2025-09-25

Hello @eogos

When you toggle a GPIO pin inside a timer interrupt callback, the pin changes state (from high to low or low to high) each time the timer overflows and triggers the interrupt. However, a complete output waveform cycle—consisting of both a rising and a falling edge—requires two toggles. As a result, the frequency of the output signal on the pin is only half the frequency at which the timer interrupt occurs. Additionally, the execution time of the TIM_IRQ handler itself can introduce delays.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.
Saket_Om