Time Project: Clock

A simple clock on STM32 with RT-Thread. A timer updates every millisecond, shows time on an LCD, and fades an LED each second.

BeginnerProtip2 hours20

Things used in this project

Hardware components

Breadboard (generic)

Jumper wires (generic)

Resistor 220 ohm

3 mm LED: Red

RT Thread Spark Development Boa

Digital Oscilloscope

Software apps and online services

STM32 CubeIDE

STM32 CubeMX

Story

Introduction:

In this project, we are taking our basic hardware skills to the next level by building a real-time clock on an STM32 microcontroller. This project displays elapsed time down to the millisecond using a hardware timer interrupt, and utilizes Pulse Width Modulation (PWM) to fade a status LED every single second. It provides a foundational understanding of how Interrupt Service Routines (ISRs) and the main application loop safely exchange information using global variables in embedded systems.

STM32CubeMX Configurations

GPIO Configuration

Figure 1. Configure GPIO for LCD

This figure shows the GPIO setup in STM32CubeMX for the STM32F407ZGTx. Pins PD3 and PF9 are configured as output pins and assigned to the LCD RESET and BACKLIGHT functions.

RTC Configuration

1 / 2 • Figure 2. Configure RTC

This figure shows the RTC configuration in STM32CubeMX. The RTC clock source is enabled and the time/date settings are configured for real-time clock operation.

Timers Configuration

1 / 2 • Figure 3. Configure TIM2

This figure shows the TIM2 configuration in STM32CubeMX. TIM2 is set to use the internal clock with PWM Generation Channel 1 enabled, and its timer parameters and interrupt settings are configured for PWM operation.

1 / 2 • Figure 4. Configure TIM3

This figures shows the TIM3 configuration in STM32CubeMX. TIM3 is configured to use the internal clock, with timer parameters and interrupt settings enabled for timing operations.

VideoDemonstration

Without Oscilloscope

Code

main.c

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2026 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 */

#include "drv_lcd.h"
#include "stdio.h"
/* 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 ---------------------------------------------------------*/
RTC_HandleTypeDef hrtc;

TIM_HandleTypeDef htim2;
TIM_HandleTypeDef htim3;

SRAM_HandleTypeDef hsram1;

/* USER CODE BEGIN PV */
volatile uint8_t updateled = 0;
volatile uint8_t lcd_update_requested = 0;

volatile uint16_t global_time = 0;

RTC_TimeTypeDef sTime = {0};
RTC_DateTypeDef sDate = {0};

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_RTC_Init(void);
static void MX_TIM2_Init(void);
static void MX_TIM3_Init(void);
static void MX_FSMC_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 == TIM2) {
		updateled = 1;
	}

	if(htim->Instance == TIM3) {
		global_time++;

		if(global_time >= 1000) {
			global_time = 0;
		}

		if(global_time % 100 == 0) {
			lcd_update_requested = 1;
		}
	}
}

void ledFade() {
	static uint32_t current_time = 0;
	uint32_t duty_cycle = 0;

	if(current_time <= 600) {
		duty_cycle = 159 - ((159 * current_time) / 600);
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_1, duty_cycle);
	} else {

	}

	current_time++;

	if(current_time >= 1000) {
		current_time = 0;
	}
}


void lcdUpdate() {
	HAL_RTC_GetTime(&hrtc, &sTime, RTC_FORMAT_BIN);
	HAL_RTC_GetDate(&hrtc, &sDate, RTC_FORMAT_BIN);

	char timeINlcd[20];

	sprintf(timeINlcd, "%02d:%02d:%02d:%03d", sTime.Hours, sTime.Minutes, sTime.Seconds, global_time);

	lcd_show_string(0, 10, 24, timeINlcd);
}


/* 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_RTC_Init();
  MX_TIM2_Init();
  MX_TIM3_Init();
  MX_FSMC_Init();
  /* USER CODE BEGIN 2 */
  HAL_TIM_Base_Start_IT(&htim2);
    HAL_TIM_Base_Start_IT(&htim3);

    HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_1);

    drv_lcd_init();
    lcd_clear(WHITE);

  /* USER CODE END 2 */

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

    /* USER CODE BEGIN 3 */
	  if(updateled == 1) {
	 		  updateled = 0;
	 		  ledFade();
	 	  }

	 	  if(lcd_update_requested == 1) {
	 		  lcd_update_requested = 0;
	 		  lcdUpdate();
	 	  }

  }
  /* USER CODE END 3 */
}

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

  /** Configure the main internal regulator output voltage
  */
  __HAL_RCC_PWR_CLK_ENABLE();
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI|RCC_OSCILLATORTYPE_LSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.LSIState = RCC_LSI_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  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_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)
  {
    Error_Handler();
  }
}

/**
  * @brief RTC Initialization Function
  * @param None
  * @retval None
  */
static void MX_RTC_Init(void)
{

  /* USER CODE BEGIN RTC_Init 0 */

  /* USER CODE END RTC_Init 0 */

  RTC_TimeTypeDef sTime = {0};
  RTC_DateTypeDef sDate = {0};

  /* USER CODE BEGIN RTC_Init 1 */

  /* USER CODE END RTC_Init 1 */

  /** Initialize RTC Only
  */
  hrtc.Instance = RTC;
  hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
  hrtc.Init.AsynchPrediv = 127;
  hrtc.Init.SynchPrediv = 255;
  hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
  hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
  hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
  if (HAL_RTC_Init(&hrtc) != HAL_OK)
  {
    Error_Handler();
  }

  /* USER CODE BEGIN Check_RTC_BKUP */

  /* USER CODE END Check_RTC_BKUP */

  /** Initialize RTC and set the Time and Date
  */
  sTime.Hours = 0x0;
  sTime.Minutes = 0x0;
  sTime.Seconds = 0x0;
  sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  sTime.StoreOperation = RTC_STOREOPERATION_RESET;
  if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }
  sDate.WeekDay = RTC_WEEKDAY_WEDNESDAY;
  sDate.Month = RTC_MONTH_JUNE;
  sDate.Date = 0x10;
  sDate.Year = 0x0;

  if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BCD) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN RTC_Init 2 */

  /* USER CODE END RTC_Init 2 */

}

/**
  * @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};
  TIM_OC_InitTypeDef sConfigOC = {0};

  /* USER CODE BEGIN TIM2_Init 1 */

  /* USER CODE END TIM2_Init 1 */
  htim2.Instance = TIM2;
  htim2.Init.Prescaler = 99;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 4294967295;
  htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  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();
  }
  if (HAL_TIM_PWM_Init(&htim2) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 0;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_PWM_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM2_Init 2 */

  /* USER CODE END TIM2_Init 2 */
  HAL_TIM_MspPostInit(&htim2);

}

/**
  * @brief TIM3 Initialization Function
  * @param 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};

  /* USER CODE BEGIN TIM3_Init 1 */

  /* USER CODE END TIM3_Init 1 */
  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 15;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 65535;
  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();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM3_Init 2 */

  /* USER CODE END TIM3_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_GPIOF_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOE_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOG_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(BACKLIGHT_LCD_GPIO_Port, BACKLIGHT_LCD_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(RESET_LCD_GPIO_Port, RESET_LCD_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin : BACKLIGHT_LCD_Pin */
  GPIO_InitStruct.Pin = BACKLIGHT_LCD_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(BACKLIGHT_LCD_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : RESET_LCD_Pin */
  GPIO_InitStruct.Pin = RESET_LCD_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(RESET_LCD_GPIO_Port, &GPIO_InitStruct);

  /* USER CODE BEGIN MX_GPIO_Init_2 */

  /* USER CODE END MX_GPIO_Init_2 */
}

/* FSMC initialization function */
static void MX_FSMC_Init(void)
{

  /* USER CODE BEGIN FSMC_Init 0 */

  /* USER CODE END FSMC_Init 0 */

  FSMC_NORSRAM_TimingTypeDef Timing = {0};

  /* USER CODE BEGIN FSMC_Init 1 */

  /* USER CODE END FSMC_Init 1 */

  /** Perform the SRAM1 memory initialization sequence
  */
  hsram1.Instance = FSMC_NORSRAM_DEVICE;
  hsram1.Extended = FSMC_NORSRAM_EXTENDED_DEVICE;
  /* hsram1.Init */
  hsram1.Init.NSBank = FSMC_NORSRAM_BANK3;
  hsram1.Init.DataAddressMux = FSMC_DATA_ADDRESS_MUX_DISABLE;
  hsram1.Init.MemoryType = FSMC_MEMORY_TYPE_SRAM;
  hsram1.Init.MemoryDataWidth = FSMC_NORSRAM_MEM_BUS_WIDTH_8;
  hsram1.Init.BurstAccessMode = FSMC_BURST_ACCESS_MODE_DISABLE;
  hsram1.Init.WaitSignalPolarity = FSMC_WAIT_SIGNAL_POLARITY_LOW;
  hsram1.Init.WrapMode = FSMC_WRAP_MODE_DISABLE;
  hsram1.Init.WaitSignalActive = FSMC_WAIT_TIMING_BEFORE_WS;
  hsram1.Init.WriteOperation = FSMC_WRITE_OPERATION_ENABLE;
  hsram1.Init.WaitSignal = FSMC_WAIT_SIGNAL_DISABLE;
  hsram1.Init.ExtendedMode = FSMC_EXTENDED_MODE_DISABLE;
  hsram1.Init.AsynchronousWait = FSMC_ASYNCHRONOUS_WAIT_DISABLE;
  hsram1.Init.WriteBurst = FSMC_WRITE_BURST_DISABLE;
  hsram1.Init.PageSize = FSMC_PAGE_SIZE_NONE;
  /* Timing */
  Timing.AddressSetupTime = 15;
  Timing.AddressHoldTime = 15;
  Timing.DataSetupTime = 255;
  Timing.BusTurnAroundDuration = 15;
  Timing.CLKDivision = 16;
  Timing.DataLatency = 17;
  Timing.AccessMode = FSMC_ACCESS_MODE_A;
  /* ExtTiming */

  if (HAL_SRAM_Init(&hsram1, &Timing, NULL) != HAL_OK)
  {
    Error_Handler( );
  }

  /* USER CODE BEGIN FSMC_Init 2 */

  /* USER CODE END FSMC_Init 2 */
}

/* USER CODE BEGIN 4 */

/* 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 */

Credits

Princess Nashema MACASERO

2 projects • 0 followers

Paul Rodolf P. Castor

22 projects • 9 followers

Time Project: Clock