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Published June 14, 2026

ADC Project: Infrared Proximity Sensor

A contactless distance measurement system using STM32's ADC to detect objects via infrared reflection and provide visual feedback through RG

BeginnerProtip1 hour36

Things used in this project

Hardware components

RT-Thread RT-Spark Development Board

Software apps and online services

STM32CubeIDE

STM32CubeMX

Story

Introduction

This project uses an infrared (IR) proximity sensor to identify close items without making physical contact. This exercise emphasizes the significance of ambient light correction and signal averaging in analog sensor design by demonstrating how embedded systems can measure reflected infrared light to determine object distance and instantaneously deliver visual feedback through an RGB LED.

Implementation

Important Elements:

Ambient Light Subtraction: Isolates the reflected signal by measuring background infrared while the LED is off.
Signal Averaging: Reduces noise and stabilizes readings by averaging twenty observations.
Analog discrepancies are mapped to six different distance ranges via distance calibration.
RGB LED Feedback: Color-coded, instantaneous visual representation of an object's proximity.

Distance Calibration:

The RGB LED indicates object proximity through color coding:

Green: No object within 20 cm
Blue: 16-20 cm
Yellow: 12-16 cm
Red: 8-12 cm
Magenta: 4-8 cm
White: 0-4 cm (very close)

Results

Observations:

RGB LED Color Change: When an object approaches the sensor, the LED's color shifts.
Detection Range: White indicates a distance of 0–4 cm, and the sensor consistently detects objects up to 20 cm away.
Noise Reduction: By averaging several samples, flickering was removed, and a steady LED output was produced.
Ambient Rejection: Constant room lighting was successfully disregarded by the background subtraction method.

Video Demonstration

Video 1. Final Output

The video shows the system in operation when an object is brought closer to the sensor. The RGB LED gently changes color as the object passes the calibrated thresholds, demonstrating the sensor's ability to measure distance in real time.

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 */

/* 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 ---------------------------------------------------------*/
ADC_HandleTypeDef hadc1;

TIM_HandleTypeDef htim2;

/* USER CODE BEGIN PV */
float voltageReading = 0;
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_ADC1_Init(void);
static void MX_TIM2_Init(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
void IRSensor(void) {
	HAL_ADC_Start(&hadc1);
	HAL_ADC_PollForConversion(&hadc1, 1);

	//HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_2);
	voltageReading = HAL_ADC_GetValue(&hadc1);
	voltageReading = (voltageReading * 3.3) / 4095.0;

	/*
		Channel1 = RED_LED
		Channel2 = GREEN_LED
		Channel3 = BLUE_LED
		Timer2, 1kHz Frequency, 16MHz Bus Frequency, 15 PSC, 999 ARR

		20cm = 1.190V
		16cm = 1.20V
		12cm = 1.280V
		8cm = 1.340V
		4cm = 2.00V
		0cm = ???
	*/
	if (voltageReading >= 3.10) {
		// Green (Far away: greater than 20cm / below 1.19V)
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_1, 0);   // R
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_2, 999); // G
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_3, 0);   // B
	}
	else if (voltageReading >= 2.50) {
		// Blue (16cm to 20cm)
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_1, 0);   // R
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_2, 0);   // G
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_3, 999); // B
	}
	else if (voltageReading >= 2.00) {
		// Yellow (12cm to 16cm) -> Red + Green
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_1, 999); // R
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_2, 224); // G
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_3, 0);   // B
	}
	else if (voltageReading >= 1.50) {
		// Red (8cm to 12cm)
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_1, 999); // R
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_2, 0);   // G
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_3, 0);   // B
	}
	else if (voltageReading >= 1.00) {
		// Magenta (4cm to 8cm)
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_1, 999); // R
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_2, 0);   // G
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_3, 699); // B
	}
	else {
		// White (Very Close: 0cm to 4cm)
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_1, 999); // R
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_2, 999); // G
		__HAL_TIM_SET_COMPARE(&htim2, TIM_CHANNEL_3, 999); // B
	}
}
/* 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_ADC1_Init();
  MX_TIM2_Init();
  /* USER CODE BEGIN 2 */
  HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_1);
  HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_2);
  HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_3);
  /* USER CODE END 2 */

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

    /* USER CODE BEGIN 3 */
	  IRSensor();
  }
  /* 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_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)
  {
    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 ADC1 Initialization Function
  * @param None
  * @retval None
  */
static void MX_ADC1_Init(void)
{

  /* USER CODE BEGIN ADC1_Init 0 */

  /* USER CODE END ADC1_Init 0 */

  ADC_ChannelConfTypeDef sConfig = {0};

  /* USER CODE BEGIN ADC1_Init 1 */

  /* USER CODE END ADC1_Init 1 */

  /** Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
  */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV8;
  hadc1.Init.Resolution = ADC_RESOLUTION_12B;
  hadc1.Init.ScanConvMode = DISABLE;
  hadc1.Init.ContinuousConvMode = DISABLE;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DMAContinuousRequests = DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
  */
  sConfig.Channel = ADC_CHANNEL_0;
  sConfig.Rank = 1;
  sConfig.SamplingTime = ADC_SAMPLETIME_480CYCLES;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN ADC1_Init 2 */

  /* USER CODE END ADC1_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 = 15;
  htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim2.Init.Period = 999;
  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();
  }
  if (HAL_TIM_PWM_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_2) != HAL_OK)
  {
    Error_Handler();
  }
  if (HAL_TIM_PWM_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_3) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM2_Init 2 */

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

}

/**
  * @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_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(Digital_Ground_GPIO_Port, Digital_Ground_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin : Digital_Ground_Pin */
  GPIO_InitStruct.Pin = Digital_Ground_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_OD;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(Digital_Ground_GPIO_Port, &GPIO_InitStruct);

  /* USER CODE BEGIN MX_GPIO_Init_2 */

  /* USER CODE END MX_GPIO_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

Marie June LOMO

8 projects • 0 followers

Paul Rodolf P. Castor

60 projects • 9 followers

ADC Project: Infrared Proximity Sensor

Things used in this project

Hardware components

Software apps and online services

Story

Introduction

Implementation

Distance Calibration:

Results

Video Demonstration

Code

main.c

GitHub Repository

Credits

Marie June LOMO

Paul Rodolf P. Castor

Comments

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ADC Project: Infrared Proximity Sensor

ADC Project: Infrared Proximity Sensor

Things used in this project

Hardware components

Software apps and online services

Story

Introduction

Implementation

Distance Calibration:

Results

Video Demonstration

Code

main.c

GitHub Repository

Credits

Marie June LOMO

Paul Rodolf P. Castor

Comments

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