STM32 Timer and Interrupt Based LED Blink for 1.5 Seconds

This code utilizes timers, external interrupts, and internal interrupts to blink the built-in LED for 1.5 seconds when the button is pressed once and turns off when the button is pressed again. The code is written for STM32 using the HAL library.

#include "stm32f4xx_hal.h"

TIM_HandleTypeDef htim2;
GPIO_InitTypeDef GPIO_InitStruct;
int led_state = 0;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM2_Init(void);

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
  if(GPIO_Pin == GPIO_PIN_0)
  {
    if(led_state == 0)
    {
      HAL_TIM_Base_Start_IT(&htim2);   // Start timer and interrupts
      led_state = 1;
    }
    else
    {
      HAL_TIM_Base_Stop_IT(&htim2);    // Stop timer and interrupts
      HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_RESET); // Turn off LED
      led_state = 0;
    }
  }
}

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
  if(htim->Instance == TIM2)
  {
    HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);  // Toggle LED
  }
}

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_TIM2_Init();

  while (1)
  {
    // Do nothing
  }
}

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;

  __HAL_RCC_PWR_CLK_ENABLE();
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    while(1);
  }

  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
  {
    while(1);
  }

  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}

static void MX_GPIO_Init(void)
{
  GPIO_InitStruct.Pin = GPIO_PIN_0;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  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);

  HAL_NVIC_SetPriority(EXTI0_IRQn, 1, 0);
  HAL_NVIC_EnableIRQ(EXTI0_IRQn);
}

static void MX_TIM2_Init(void)
{
  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 4999;   // Prescaler value for 1ms
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 1500;      // 1.5 seconds
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  HAL_TIM_Base_Init(&htim2);

  HAL_NVIC_SetPriority(TIM2_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(TIM2_IRQn);
}

Key Details

• Prescaler: 4999, resulting in a 1ms timer tick (assuming a system clock of 84MHz).
• Timer: TIM2
• Counter Period: 1500, representing 1.5 seconds at a 1ms tick.

Code Explanation

The code utilizes an external interrupt triggered by a button press on GPIO_PIN_0. The interrupt handler toggles the led_state variable, initiating or stopping the timer (TIM2) and the corresponding internal interrupt.

The internal interrupt, triggered every 1.5 seconds by TIM2, toggles the LED connected to GPIO_PIN_5 using HAL_GPIO_TogglePin().

Note: The GPIO pins used for the button and LED (GPIO_PIN_0 and GPIO_PIN_5) may need to be adjusted depending on your hardware setup.