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Measuring speed and distance with hall sensor

jberdkan
Associate II

‎2025-04-12 3:29 PM

Hi everyone, I am trying to use the m5 stack hall sensor to measure the speed and distance that an athlete is going. I want to attach the hall sensor to the drum of the machine and measure it. I am having some trouble with getting zero values even when I move the magnet. The source code I found was arduino but I changed it for it to work on the STM32IDE. I am using TIM4 for my timers and PB7 to read in the digital values, also it is good to mention that i have the PB7 as a GPIO EXTI. Can anyone look at the code and see if something is wrong? 

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2025 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"
#include "cmsis_os.h"
#include "usb_host.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <string.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 */
#define Hall_Sensor_Pin GPIO_PIN_7
#define Hall_Sensor_Port GPIOB
/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
I2C_HandleTypeDef hi2c2;

I2S_HandleTypeDef hi2s3;

QSPI_HandleTypeDef hqspi;

TIM_HandleTypeDef htim4;

UART_HandleTypeDef huart2;

SRAM_HandleTypeDef hsram1;

/* Definitions for HallSensorTask */
osThreadId_t HallSensorTaskHandle;
const osThreadAttr_t HallSensorTask_attributes = {
  .name = "HallSensorTask",
  .stack_size = 256 * 4,
  .priority = (osPriority_t) osPriorityNormal,
};
/* USER CODE BEGIN PV */
//Radius or drum and derived constants
float radius = 3.0f;	//inches
float circumference;	//inches (2*pi*r)

//Speed calculation variables
volatile int reedVal;
volatile uint32_t timer = 0;			//millisecond counter
volatile uint32_t reedCounter;		//for debouncing
volatile float mph = 0.0f;
const int maxReedCounter = 100;			//debouncing time in ms


/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_FSMC_Init(void);
static void MX_I2C2_Init(void);
static void MX_I2S3_Init(void);
static void MX_QUADSPI_Init(void);
static void MX_TIM4_Init(void);
static void MX_USART2_UART_Init(void);
void StartHallSensorTask(void *argument);

/* 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_FSMC_Init();
  MX_I2C2_Init();
  MX_I2S3_Init();
  MX_QUADSPI_Init();
  MX_TIM4_Init();
  MX_USART2_UART_Init();
  /* USER CODE BEGIN 2 */
  HAL_TIM_Base_Start_IT(&htim4);
  /* USER CODE END 2 */

  /* Init scheduler */
  osKernelInitialize();

  /* USER CODE BEGIN RTOS_MUTEX */
  /* add mutexes, ... */
  /* USER CODE END RTOS_MUTEX */

  /* USER CODE BEGIN RTOS_SEMAPHORES */
  /* add semaphores, ... */
  /* USER CODE END RTOS_SEMAPHORES */

  /* USER CODE BEGIN RTOS_TIMERS */
  /* start timers, add new ones, ... */
  /* USER CODE END RTOS_TIMERS */

  /* USER CODE BEGIN RTOS_QUEUES */
  /* add queues, ... */
  /* USER CODE END RTOS_QUEUES */

  /* Create the thread(s) */
  /* creation of HallSensorTask */
  HallSensorTaskHandle = osThreadNew(StartHallSensorTask, NULL, &HallSensorTask_attributes);

  /* USER CODE BEGIN RTOS_THREADS */
  /* add threads, ... */
  /* USER CODE END RTOS_THREADS */

  /* USER CODE BEGIN RTOS_EVENTS */
  /* add events, ... */
  /* USER CODE END RTOS_EVENTS */

  /* Start scheduler */
  osKernelStart();

  /* We should never get here as control is now taken by the scheduler */
  /* 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};

  /** 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_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 4;
  RCC_OscInitStruct.PLL.PLLN = 72;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 3;
  RCC_OscInitStruct.PLL.PLLR = 2;
  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 I2C2 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_I2C2_Init(void)
{

  /* USER CODE BEGIN I2C2_Init 0 */

  /* USER CODE END I2C2_Init 0 */

  /* USER CODE BEGIN I2C2_Init 1 */

  /* USER CODE END I2C2_Init 1 */
  hi2c2.Instance = I2C2;
  hi2c2.Init.ClockSpeed = 100000;
  hi2c2.Init.DutyCycle = I2C_DUTYCYCLE_2;
  hi2c2.Init.OwnAddress1 = 0;
  hi2c2.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
  hi2c2.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
  hi2c2.Init.OwnAddress2 = 0;
  hi2c2.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
  hi2c2.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
  if (HAL_I2C_Init(&hi2c2) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN I2C2_Init 2 */

  /* USER CODE END I2C2_Init 2 */

}

/**
  * @brief I2S3 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_I2S3_Init(void)
{

  /* USER CODE BEGIN I2S3_Init 0 */

  /* USER CODE END I2S3_Init 0 */

  /* USER CODE BEGIN I2S3_Init 1 */

  /* USER CODE END I2S3_Init 1 */
  hi2s3.Instance = SPI3;
  hi2s3.Init.Mode = I2S_MODE_MASTER_TX;
  hi2s3.Init.Standard = I2S_STANDARD_PHILIPS;
  hi2s3.Init.DataFormat = I2S_DATAFORMAT_16B;
  hi2s3.Init.MCLKOutput = I2S_MCLKOUTPUT_ENABLE;
  hi2s3.Init.AudioFreq = I2S_AUDIOFREQ_32K;
  hi2s3.Init.CPOL = I2S_CPOL_LOW;
  hi2s3.Init.ClockSource = I2S_CLOCK_PLL;
  hi2s3.Init.FullDuplexMode = I2S_FULLDUPLEXMODE_ENABLE;
  if (HAL_I2S_Init(&hi2s3) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN I2S3_Init 2 */

  /* USER CODE END I2S3_Init 2 */

}

/**
  * @brief QUADSPI Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_QUADSPI_Init(void)
{

  /* USER CODE BEGIN QUADSPI_Init 0 */

  /* USER CODE END QUADSPI_Init 0 */

  /* USER CODE BEGIN QUADSPI_Init 1 */

  /* USER CODE END QUADSPI_Init 1 */
  /* QUADSPI parameter configuration*/
  hqspi.Instance = QUADSPI;
  hqspi.Init.ClockPrescaler = 0;
  hqspi.Init.FifoThreshold = 4;
  hqspi.Init.SampleShifting = QSPI_SAMPLE_SHIFTING_HALFCYCLE;
  hqspi.Init.FlashSize = 24;
  hqspi.Init.ChipSelectHighTime = QSPI_CS_HIGH_TIME_5_CYCLE;
  hqspi.Init.ClockMode = QSPI_CLOCK_MODE_0;
  hqspi.Init.FlashID = QSPI_FLASH_ID_1;
  hqspi.Init.DualFlash = QSPI_DUALFLASH_DISABLE;
  if (HAL_QSPI_Init(&hqspi) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN QUADSPI_Init 2 */

  /* USER CODE END QUADSPI_Init 2 */

}

/**
  * @brief TIM4 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_TIM4_Init(void)
{

  /* USER CODE BEGIN TIM4_Init 0 */

  /* USER CODE END TIM4_Init 0 */

  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};

  /* USER CODE BEGIN TIM4_Init 1 */

  /* USER CODE END TIM4_Init 1 */
  htim4.Instance = TIM4;
  htim4.Init.Prescaler = 7;
  htim4.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim4.Init.Period = 1999;
  htim4.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim4.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  if (HAL_TIM_Base_Init(&htim4) != HAL_OK)
  {
    Error_Handler();
  }
  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim4, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim4, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN TIM4_Init 2 */

  /* USER CODE END TIM4_Init 2 */

}

/**
  * @brief USART2 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_USART2_UART_Init(void)
{

  /* USER CODE BEGIN USART2_Init 0 */

  /* USER CODE END USART2_Init 0 */

  /* USER CODE BEGIN USART2_Init 1 */

  /* USER CODE END USART2_Init 1 */
  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN USART2_Init 2 */

  /* USER CODE END USART2_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_GPIOE_CLK_ENABLE();
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOF_CLK_ENABLE();
  __HAL_RCC_GPIOH_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOG_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOE, LED3_Pin|LED4_Pin|LED1_Pin|LED2_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOF, LCD_BLCTRL_Pin|EXT_RESET_Pin|CTP_RST_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LCD_RESET_GPIO_Port, LCD_RESET_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(USB_OTGFS_PPWR_EN_GPIO_Port, USB_OTGFS_PPWR_EN_Pin, GPIO_PIN_SET);

  /*Configure GPIO pins : LED3_Pin LED4_Pin LED1_Pin LED2_Pin */
  GPIO_InitStruct.Pin = LED3_Pin|LED4_Pin|LED1_Pin|LED2_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_OD;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);

  /*Configure GPIO pin : DFSDM_DATIN3_Pin */
  GPIO_InitStruct.Pin = DFSDM_DATIN3_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF8_DFSDM1;
  HAL_GPIO_Init(DFSDM_DATIN3_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pins : LCD_BLCTRL_Pin EXT_RESET_Pin CTP_RST_Pin */
  GPIO_InitStruct.Pin = LCD_BLCTRL_Pin|EXT_RESET_Pin|CTP_RST_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOF, &GPIO_InitStruct);

  /*Configure GPIO pin : DFSDM_CKOUT_Pin */
  GPIO_InitStruct.Pin = DFSDM_CKOUT_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF8_DFSDM1;
  HAL_GPIO_Init(DFSDM_CKOUT_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : JOY_SEL_Pin */
  GPIO_InitStruct.Pin = JOY_SEL_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(JOY_SEL_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : DFSDM_DATIN0_Pin */
  GPIO_InitStruct.Pin = DFSDM_DATIN0_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF8_DFSDM1;
  HAL_GPIO_Init(DFSDM_DATIN0_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pins : JOY_RIGHT_Pin JOY_LEFT_Pin */
  GPIO_InitStruct.Pin = JOY_RIGHT_Pin|JOY_LEFT_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(GPIOF, &GPIO_InitStruct);

  /*Configure GPIO pins : JOY_UP_Pin JOY_DOWN_Pin LCD_TE_Pin USB_OTGFS_OVRCR_Pin */
  GPIO_InitStruct.Pin = JOY_UP_Pin|JOY_DOWN_Pin|LCD_TE_Pin|USB_OTGFS_OVRCR_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(GPIOG, &GPIO_InitStruct);

  /*Configure GPIO pin : M2_CKIN_Pin */
  GPIO_InitStruct.Pin = M2_CKIN_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF5_SPI1;
  HAL_GPIO_Init(M2_CKIN_GPIO_Port, &GPIO_InitStruct);

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

  /*Configure GPIO pins : CODEC_INT_Pin CTP_INT_Pin */
  GPIO_InitStruct.Pin = CODEC_INT_Pin|CTP_INT_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(GPIOG, &GPIO_InitStruct);

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

  /*Configure GPIO pins : uSD_D0_Pin uSD_D1_Pin uSD_D2_Pin uSD_D3_Pin
                           uSD_CLK_Pin */
  GPIO_InitStruct.Pin = uSD_D0_Pin|uSD_D1_Pin|uSD_D2_Pin|uSD_D3_Pin
                          |uSD_CLK_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF12_SDIO;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  /*Configure GPIO pin : M2_CKINA8_Pin */
  GPIO_InitStruct.Pin = M2_CKINA8_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF0_MCO;
  HAL_GPIO_Init(M2_CKINA8_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : uSD_CMD_Pin */
  GPIO_InitStruct.Pin = uSD_CMD_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF12_SDIO;
  HAL_GPIO_Init(uSD_CMD_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : uSD_DETECT_Pin */
  GPIO_InitStruct.Pin = uSD_DETECT_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(uSD_DETECT_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : I2C1_SCL_Pin */
  GPIO_InitStruct.Pin = I2C1_SCL_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
  GPIO_InitStruct.Alternate = GPIO_AF4_I2C1;
  HAL_GPIO_Init(I2C1_SCL_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pin : Hall_Sensor_Pin */
  GPIO_InitStruct.Pin = Hall_Sensor_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_FALLING;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  HAL_GPIO_Init(Hall_Sensor_GPIO_Port, &GPIO_InitStruct);

  /* EXTI interrupt init*/
  HAL_NVIC_SetPriority(EXTI9_5_IRQn, 5, 0);
  HAL_NVIC_EnableIRQ(EXTI9_5_IRQn);

/* 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_BANK1;
  hsram1.Init.DataAddressMux = FSMC_DATA_ADDRESS_MUX_DISABLE;
  hsram1.Init.MemoryType = FSMC_MEMORY_TYPE_SRAM;
  hsram1.Init.MemoryDataWidth = FSMC_NORSRAM_MEM_BUS_WIDTH_16;
  hsram1.Init.BurstAccessMode = FSMC_BURST_ACCESS_MODE_DISABLE;
  hsram1.Init.WaitSignalPolarity = FSMC_WAIT_SIGNAL_POLARITY_LOW;
  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.ContinuousClock = FSMC_CONTINUOUS_CLOCK_SYNC_ONLY;
  hsram1.Init.WriteFifo = FSMC_WRITE_FIFO_ENABLE;
  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 */



void UART_Print(char* msg){
	HAL_UART_Transmit(&huart2, (uint8_t*)msg, strlen(msg), HAL_MAX_DELAY);
}

/*void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin){
	if (GPIO_Pin == Hall_Sensor_Pin && reedCounter == 0) {
	        mph = (56.8f * circumference) / (float)timer;
	        timer = 0;
	        reedCounter = maxReedCounter;
	    }
}*/

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) {
    if (htim->Instance == TIM4) {
    	//timer interrupt code
    	reedVal = HAL_GPIO_ReadPin(Hall_Sensor_Port, Hall_Sensor_Pin);	//read
    	if (reedVal == GPIO_PIN_SET){	//if reed is closed
    		if (reedCounter == 0)
    		{
    			mph = (56.8 * circumference) / timer;	//calculate miles per hour
    			timer = 0;	//reset timer
    			reedCounter = maxReedCounter;	//reset reedCounter
    		}
    		else{
    			if (reedCounter > 0){
    				reedCounter --;
    			}
    		}
    	}
    	else {
    		if (reedCounter > 0){
    			reedCounter -- ;
    		}
    	}
    	if (timer > 2000)
    	{
    		mph = 0;
    	}
    	else {
    		timer =+1;
    	}
    }
}

/* USER CODE END 4 */

/* USER CODE BEGIN Header_StartHallSensorTask */
/**
  * @brief  Function implementing the HallSensorTask thread.
  * @PAram  argument: Not used
  * @retval None
  */
/* USER CODE END Header_StartHallSensorTask */
void StartHallSensorTask(void *argument)
{
  /* init code for USB_HOST */
  MX_USB_HOST_Init();
  char buffer[64];
  /* USER CODE BEGIN 5 */
  /* Infinite loop */
  for(;;)
  {
	  /*mph = (56.8f * circumference) / (float)timer_ms;
	 timer_ms = 0;
	 reedCounter = maxReedCounter;*/
	  sprintf(buffer, "Speed = %.2f MPH\r\n", mph);
	  UART_Print(buffer);
	 osDelay(1000);
  }
  /* USER CODE END 5 */
}

/**
  * @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 */

I am also doing everything in FreeRTOS since the client wants all the data to be given in real time. 

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2 REPLIES 2
TDK
Super User

‎2025-04-13 7:04 AM - edited ‎2025-04-13 7:04 AM

So a switch closes once per revolution to indicate speed, and you want to track the duration between when the switch closes?

Set up a high speed 32-bit timer (HAL_GetTick can be used for testing), set the pin as EXTI on falling edge, and in the EXTI callback, calculate the difference in ticks between successful calls. Your polling method may not be quick enough and certainly won't be as accurate as it could be.

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jberdkan
Associate II
In response to TDK

‎2025-04-13 11:48 AM

Yes, that’s exactly what I’m trying to do — I have a Hall effect sensor that outputs a digital LOW pulse once per revolution, and I’m trying to calculate the time between those pulses to derive speed.

I’ve already set up TIM4 as a 32-bit timer and configured PB7 as an input capture pin (TIM4_CH2), so I’m capturing the falling edge with a callback. I’m storing the captured value and computing the delta between two successive events to get the duration between revolutions.

I was originally using polling and then input capture via HAL TIM IC Capture Callback(), but ran into an issue where the captured value (CCR2) seemed to remain at zero, or wouldn't update. I’ll definitely look into trying EXTI on the falling edge of the signal instead — that might help simplify the logic and avoid relying on the input capture if that’s what's causing the issue.

I appreciate the tip about using HAL_GetTick() for testing — it might help isolate where things are going wrong.

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