In this STM32 Nucleo tutorial, we will learn how to configure and handle timer interrupts using HAL Library in STM32Cube IDE. We will demonstrate this through an example by toggling an LED after a set number of time.
Timer interrupts in STM32 pause the sequential execution of a program loop() function for a predefined number of seconds (timed intervals) to execute a different set of commands. After the set commands are executed, the program resumes again from the same position. The Nucleo STM32F103 comes with four timers known as TIM1, TIM2, TIM3, and TIM4. They act as a clock and are used to keep track of time based events. We will show you how to program these timers in STM32Cube IDE using HAL Library.
By the end of this article you will be able to know about:
- How to set up a timer interrupt in STM32
- Configure GPIO Output Pin using STM32Cube IDE
- Toggling the output pin after every 500 milliseconds by setting the Prescaler and Preload value
- ISR that toggles the LED after every interrupt
We will guide you step by step on how to configure timer interrupts for Nucleo STM32 using STM32Cube IDE. We will aim to toggle an LED after every interrupt.
Timer Interrupt to toggle LED
Now we will learn how to handle interrupts in the Nucleo STM32 to toggle an LED. The LED will be set up as a digital output. The LED will be toggled after a set number of intervals.
we will be using STM32103RB Nucleo board and will toggle onboard LED.
As we know that pin A5 is connected with the onboard LED. You can also use any appropriate Nucleo STM32 digital pin to connect with external LED (connect the anode pin of LED with the pin of your choice, and the cathode pin with the common ground through the 220-ohm resistor).
Program Timer Interrupts with STM32 Nucleo in STM32Cube IDE
We will use STM32Cube IDE to program our STM32 board. Open the IDE and head over to a new project.
Then for the target selection, specify the STM32 Nucleo board number. After that click at the column as shown in the picture below. Then click the ‘Next’ button.
The following window will open. Here specify the name of your project then click ‘Finish’ to complete the setup of your project.
Device Configuration Tool
Configuring TIM2
Here comes the important part where we will configure the timer interrupt. For this project we will use TIM2. So head over to Timers > TIM2 and set the clock source as ‘Internal Clock.’
Our aim is that TIM2 should generate an interrupt after every 500ms (0.5s). To set a particular output time we will have to set the Prescaler value, the clock frequency, and the timer preload register’s value.
Tout= (Prescaler x Preload)/Clock Frequency
As the Nucleo STM32 microcontroller has a maximum clock speed of 72 MHz therefore let us use this frequency. When using 72 MHz Clock frequency, Precaler value as 1000 and output time as 500ms, the Preload value will come out to be (0.5*72*1000000)/1000 = 36000.
You may use appropriate values according to your project.
Next we will specify the Prescaler and Preload (Counter Period) values in the Parameter Settings. We have set 1000 as the Prescaler and 36000 as the Preload. Also, enable the auto-reload preload feature as shown below.
Now click NVIC Settings and enable the interrupt for TIM2 global interrupt as shown below.
Now go to System Core > RCC then select ‘Crystal/Ceramic Resonator’ from the High Speed Clock feature.
We have enabled the RCC external clock source.
Clock Configuration
Next go to the Clock Configuration found at the top. This will open the following window. Here we will select the clock frequency.
You can specify your system clock. We will set it as 72 MHz. These are the configurations we have set:
Now we will configure the output pin. For the output pin we have chosen the digital pin PA5. PA5 is connected with the onboard LED as mentioned before. Click at PA 5 and set it as GPIO_Output.
Now we will save our file. Press Ctrl + S. The following window will appear. Click ‘Yes.’ This will generate a template code for you.
Another window will appear that will ask if you want to open the perspective. Click ‘Yes.’
Timer Interrupts with STM32 Nucleo Code
Now the following page opens. On the right side you will be able to view the Outline of the code. This happened because we opened our code with perspective.
In the centre you can view the main.c file and on the left you can view the Project Explorer. If you want to go to the Device Configuration Tool, then click the .ioc tab.
Now let us look at our main.c file that was generated.
Look for the MX_GPIO_Init() function.
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_GPIOD_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_RESET);
/*Configure GPIO pin : PA5 */
GPIO_InitStruct.Pin = GPIO_PIN_5;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}This is the function that initializes the GPIO pin that we have set up in the Device Configuration Tool. Here as you can see Pin A5 is configured as an output pin with no pull. This means that the pin A5 is setup in high impedance. The set up speed is set to low frequency.
The HAL_GPIO_Init() function is then called for the pin. This function takes in two parameters. The first parameter is the GPIO Port which is GPIOA in our case. The second parameter is &GPIO_InitStruct.
Look for the MX_TIM2_Init() function.
static void MX_TIM2_Init(void)
{
/* USER CODE BEGIN TIM2_Init 0 */
/* USER CODE END TIM2_Init 0 */
TIM_ClockConfigTypeDef sClockSourceConfig = {0};
TIM_MasterConfigTypeDef sMasterConfig = {0};
/* USER CODE BEGIN TIM2_Init 1 */
/* USER CODE END TIM2_Init 1 */
htim2.Instance = TIM2;
htim2.Init.Prescaler = 1000;
htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
htim2.Init.Period = 36000;
htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
{
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != 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 */
}
This is the function that initializes the TIM2 interrupt on the set Prescaler, Preload and Clock frequency values.
Modifying Code
Inside the main.c file, make sure the following code is part of your script by including the lines of code given below.
#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 */
/* 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_Base_Start_IT(&htim2);
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
.
.
.
.
/* USER CODE BEGIN 4 */
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef* htim)
{
HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
}
/* USER CODE END 4 */We will first enable the timer in the following lines:
TIM_HandleTypeDef htim2;
HAL_TIM_Base_Start_IT(&htim2);Then we will add the timer interrupt ISR handler callback function. It is responsible to check the interrupt pin source, then toggle the output GPIO pin accordingly.
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef* htim)
{
HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
}You can view the the timer interrupt handler in the stm32f1xx_it.c file.
void TIM2_IRQHandler(void)
{
HAL_TIM_IRQHandler(&htim2);
}The timer interrupt ISR handler callback function name is provided in the timer interrupt handler routine.
void HAL_TIM_IRQHandler(TIM_HandleTypeDef *htim)
{
/* TIM Update event */
if (__HAL_TIM_GET_FLAG(htim, TIM_FLAG_UPDATE) != RESET)
{
if (__HAL_TIM_GET_IT_SOURCE(htim, TIM_IT_UPDATE) != RESET)
{
__HAL_TIM_CLEAR_IT(htim, TIM_IT_UPDATE);
#if (USE_HAL_TIM_REGISTER_CALLBACKS == 1)
htim->PeriodElapsedCallback(htim);
#else
HAL_TIM_PeriodElapsedCallback(htim);
#endif /* USE_HAL_TIM_REGISTER_CALLBACKS */
}
}
}main.c file
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2024 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 */
/* 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_Base_Start_IT(&htim2);
/* 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_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
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_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != 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_ClockConfigTypeDef sClockSourceConfig = {0};
TIM_MasterConfigTypeDef sMasterConfig = {0};
/* USER CODE BEGIN TIM2_Init 1 */
/* USER CODE END TIM2_Init 1 */
htim2.Instance = TIM2;
htim2.Init.Prescaler = 1000;
htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
htim2.Init.Period = 36000;
htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
{
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != 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_InitTypeDef GPIO_InitStruct = {0};
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOD_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_RESET);
/*Configure GPIO pin : PA5 */
GPIO_InitStruct.Pin = GPIO_PIN_5;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}
/* USER CODE BEGIN 4 */
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef* htim)
{
HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
}
/* 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 */
Save the main.c file after modifying it. Now we are ready to build our project.
Building the Project
To build our project press Ctrl + B or go to Project > Build All.
Your project will start building. After a few moments, your project will be successfully built if there are no errors.
Demonstration
Next press the RUN button in the IDE. The ‘Edit configuration’ window will open up. Click ‘OK’.
After a few moments, the code will be successfully sent to the STM32 board.
Otherwise, press the RESET button on your STM32 board.
The LED will start blinking every 0.5 seconds.
Watch the demonstration video below to have a better insight.
You may also like to read:
- STM32 Nucleo GPIO Pins with LED Blinking using STM32CubeIDE
- Push Button with STM32 Nucleo using STM32CubeIDE
- GPIO External Interrupts STM32 Nucleo with STM32CubeIDE
- STM32 Nucleo UART Communication Tutorial with CubeIDE and HAL Libraries
- STM32 Nucleo UART Interrupt with STM32CubeIDE and HAL Libraries
- STM32 Nucleo UART DMA with STM32CubeIDE and HAL Libraries