•

Paul Rodolf P. Castor

Published June 11, 2026

RT-Spark LCD Clock

This project combines timer interrupts, an LCD display, and PWM to create a digital clock with an LED fading effect.

BeginnerProtip33

Things used in this project

Hardware components

ST STM32L4, STM32F7 Nucleo 144 STM32F7

Resistor 220 ohm

LED (generic)

Digital Oscilloscope

RT-Thread Spark Development Board

Software apps and online services

STMicroelectronics STM32CUBEPROG

Hand tools and fabrication machines

Breadboard, 170 Pin

10 Pc. Jumper Wire Kit, 5 cm Long

Story

Introduction

For this project, I built a simple digital clock using an STM32 microcontroller. The clock displays real-time information on an LCD while a PWM-controlled LED creates a fading effect every second. This project helped me understand how timer interrupts, LCD displays, and PWM work together in an embedded system.

STM32CubeMXConfigurations

GPIOPin Setup

The GPIO pins used in the project were configured according to their specific functions. Pins connected to the LCD were set as Output Push-Pull outputs with low-speed settings to provide stable control of the display and its backlight.

Figure 1. GPIO Setup for LCD Control

Real-Time Clock (RTC) Settings

The RTC module was enabled to keep track of the current date and time. It was configured to use the default calendar values and operates in a 24-hour time format.

Figure 2. RTC Module Setup

TIM2 PWM Configuration

TIM2 was configured to generate a PWM signal using Channel 1. The timer uses the internal clock source, and the necessary timer and interrupt settings were enabled to support PWM operation.

Figure 3. TIM2 PWM Configuration

The TIM2 global interrupt was enabled through the NVIC Settings tab.

Figure 3.2. TIM2 NVIC Configuration

TIM3 Timing Configuration

TIM3 was set up as a timing timer using the internal clock source. Timer interrupts were enabled to allow the microcontroller to perform periodic timing-related tasks during program execution.

Figure 4. TIM3 Timer Setup

TIM3 was configured to use the internal clock with a prescaler value of 15 and a counter period of 999.

Figure 4.2. TIM3 NVIC Setup

Project Video Demonstration

Project Output

Oscilloscope Output

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 Dianne ESTORES

7 projects • 0 followers

Paul Rodolf P. Castor

74 projects • 11 followers

RT-Spark LCD Clock

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Real-Time Clock (RTC) Settings

TIM2 PWM Configuration

TIM3 Timing Configuration

Project Video Demonstration

Schematics

Pin Diagram

Code

main.c

Github Repository

Credits

Princess Dianne ESTORES

Paul Rodolf P. Castor

Comments

Embed the widget on your own site

RT-Spark LCD Clock

RT-Spark LCD Clock

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction

Real-Time Clock (RTC) Settings

TIM2 PWM Configuration

TIM3 Timing Configuration

Project Video Demonstration

Schematics

Pin Diagram

Code

main.c

Github Repository

Credits

Princess Dianne ESTORES

Paul Rodolf P. Castor

Comments

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