[STM32F103C8T6 + ICM20948] IMU not detected when using FreeRTOS with I2C.

[Piyoosh]

Hi everyone,

I'm working on a project using the STM32F103C8T6 microcontroller and the ICM-20948 IMU sensor, connected via I2C. I'm using STM32CubeIDE with FreeRTOS integration.

In a bare-metal (non-RTOS) project, the IMU communicates correctly. The device address is detected properly, and I get valid accel/gyro data.

When I move to a FreeRTOS-based project using the same I2C configuration, the IMU fails to respond.The device address is not found, and I get errors from HAL_I2C_Mem_Read().I've confirmed that I2C are initialized before osKernelStart().

 want to reliably read IMU data (ICM20948) using I2C  + FreeRTOS on STM32F103C8T6.
Can anyone who has done this successfully share suggestions or example code?

 

[Ozone]

The timing differs, and FreeRTOS grabs and manages interrupts.

You need to take a scope / logic analyser, and find out where it fails.

[mƎALLEm]

If it works in baremetal that's definitely not a hardware issue, but something related to your integration and how are you implementing the sensor reading in the task.

As @Ozone said, most probably it's a timing issue. Check the task priority versus others. Check the interrupt priorities versus others. 

[Piyoosh]

Thanks for responding

I am using only one task in setup. 

this line --- HAL_I2C_Mem_Read(&hi2c1, (0x69 << 1), 0x00, 1, &check,1, 100); is properly return check value "234"(0xEA) in bare-metal (non-RTOS) project which is show that sensor is available  to read data, but in RTOS project (i include Free Rtos code bellow) it is reading 8 value of check.

/* 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"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "i2c.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 ---------------------------------------------------------*/
CRC_HandleTypeDef hcrc;

I2C_HandleTypeDef hi2c1;
I2C_HandleTypeDef hi2c2;

UART_HandleTypeDef huart1;

osThreadId defaultTaskHandle;
/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_I2C2_Init(void);
static void MX_CRC_Init(void);
static void MX_USART1_UART_Init(void);
static void MX_I2C1_Init(void);
void StartDefaultTask(void const * 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_I2C2_Init();
 MX_CRC_Init();
 MX_USART1_UART_Init();
 MX_I2C1_Init();
 /* USER CODE BEGIN 2 */

 /* USER CODE END 2 */

 /* 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) */
 /* definition and creation of defaultTask */
 osThreadDef(defaultTask, StartDefaultTask, osPriorityNormal, 0, 128);
 defaultTaskHandle = osThreadCreate(osThread(defaultTask), NULL);

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

 /* 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};

 /** 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.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
 RCC_OscInitStruct.HSIState = RCC_HSI_ON;
 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
 RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
 RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
 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 CRC Initialization Function
 * @PAram None
 * @retval None
 */
static void MX_CRC_Init(void)
{

 /* USER CODE BEGIN CRC_Init 0 */

 /* USER CODE END CRC_Init 0 */

 /* USER CODE BEGIN CRC_Init 1 */

 /* USER CODE END CRC_Init 1 */
 hcrc.Instance = CRC;
 if (HAL_CRC_Init(&hcrc) != HAL_OK)
 {
 Error_Handler();
 }
 /* USER CODE BEGIN CRC_Init 2 */

 /* USER CODE END CRC_Init 2 */

}

/**
 * @brief I2C1 Initialization Function
 * @PAram None
 * @retval None
 */
static void MX_I2C1_Init(void)
{

 /* USER CODE BEGIN I2C1_Init 0 */

 /* USER CODE END I2C1_Init 0 */

 /* USER CODE BEGIN I2C1_Init 1 */

 /* USER CODE END I2C1_Init 1 */
 hi2c1.Instance = I2C1;
 hi2c1.Init.ClockSpeed = 100000;
 hi2c1.Init.DutyCycle = I2C_DUTYCYCLE_2;
 hi2c1.Init.OwnAddress1 = 0;
 hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
 hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
 hi2c1.Init.OwnAddress2 = 0;
 hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
 hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
 if (HAL_I2C_Init(&hi2c1) != HAL_OK)
 {
 Error_Handler();
 }
 /* USER CODE BEGIN I2C1_Init 2 */

 /* USER CODE END I2C1_Init 2 */

}

/**
 * @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 USART1 Initialization Function
 * @PAram None
 * @retval None
 */
static void MX_USART1_UART_Init(void)
{

 /* USER CODE BEGIN USART1_Init 0 */

 /* USER CODE END USART1_Init 0 */

 /* USER CODE BEGIN USART1_Init 1 */

 /* USER CODE END USART1_Init 1 */
 huart1.Instance = USART1;
 huart1.Init.BaudRate = 115200;
 huart1.Init.WordLength = UART_WORDLENGTH_8B;
 huart1.Init.StopBits = UART_STOPBITS_1;
 huart1.Init.Parity = UART_PARITY_NONE;
 huart1.Init.Mode = UART_MODE_TX_RX;
 huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
 huart1.Init.OverSampling = UART_OVERSAMPLING_16;
 if (HAL_UART_Init(&huart1) != HAL_OK)
 {
 Error_Handler();
 }
 /* USER CODE BEGIN USART1_Init 2 */

 /* USER CODE END USART1_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_GPIOC_CLK_ENABLE();
 __HAL_RCC_GPIOD_CLK_ENABLE();
 __HAL_RCC_GPIOA_CLK_ENABLE();
 __HAL_RCC_GPIOB_CLK_ENABLE();

 /*Configure GPIO pin Output Level */
 HAL_GPIO_WritePin(GPIOA, GPIO_PIN_7, GPIO_PIN_RESET);

 /*Configure GPIO pin : PA7 */
 GPIO_InitStruct.Pin = GPIO_PIN_7;
 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);

 /* USER CODE BEGIN MX_GPIO_Init_2 */

 /* USER CODE END MX_GPIO_Init_2 */
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

/* USER CODE BEGIN Header_StartDefaultTask */
/**
 * @brief Function implementing the defaultTask thread.
 * @PAram argument: Not used
 * @retval None
 */
/* USER CODE END Header_StartDefaultTask */
void StartDefaultTask(void const * argument)
{
	uint8_t check;
 /* USER CODE BEGIN 5 */
	HAL_I2C_Mem_Read(&hi2c1, (0x69 << 1), 0x00, 1, &check,1, 100);
	if (check==234)
	{
		HAL_GPIO_WritePin(GPIOA, GPIO_PIN_7, GPIO_PIN_SET);
	}
	else
	{
		HAL_GPIO_WritePin(GPIOA, GPIO_PIN_7, GPIO_PIN_RESET);
	}


 /* Infinite loop */
 for(;;)
 {
	 ICM20948_Read_Accel(&hi2c1, &ICMData, ICM20948_ADDR);
 osDelay(100);
 }
 /* USER CODE END 5 */
}

/**
 * @brief Period elapsed callback in non blocking mode
 * @note This function is called when TIM1 interrupt took place, inside
 * HAL_TIM_IRQHandler(). It makes a direct call to HAL_IncTick() to increment
 * a global variable "uwTick" used as application time base.
 * @PAram htim : TIM handle
 * @retval None
 */
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
 /* USER CODE BEGIN Callback 0 */

 /* USER CODE END Callback 0 */
 if (htim->Instance == TIM1)
 {
 HAL_IncTick();
 }
 /* USER CODE BEGIN Callback 1 */

 /* USER CODE END Callback 1 */
}

/**
 * @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 */

 

[mƎALLEm]

You need to probe what is going-on on the bus using an oscilloscope or a logic analyzer.

You need also to refer to the sensor datasheet to know what that "8" value means!

Try also to declare uint8_t check; global and test.

[Devirajkumar17]

Hello Piyoosh,

this is Rajkumar STM32H562RGT6: ICM‑20948 & ICP201xx init() hangs only when FreeRTOS is enabled — works in bare-metal same help me solve this problem 

[Andrew Neil]

---

@Devirajkumar17 wrote:

this is Rajkumar STM32H562RGT6: ICM‑20948 & ICP201xx init() hangs only when FreeRTOS is enabled — works in bare-metal same help me solve this problem 

---

You have a separate thread on this here.

The key difference between your situation and this thread is that you are using Arduino - that's an entirely different setup!