2025-06-10 11:57 PM
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?
Solved! Go to Solution.
2025-06-12 1:49 AM - edited 2025-06-12 2:27 AM
@Piyoosh wrote:what should i check now ?
You need to check why it's not initialising!
PS:
eg, is the initialisation even being called at all?
are you getting errors in the initialisation?
Again, you have working code as a reference - so compare & contrast what happens in that working code to what happens in the non-working code ...
2025-06-11 1:18 AM
The timing differs, and FreeRTOS grabs and manages interrupts.
You need to take a scope / logic analyser, and find out where it fails.
2025-06-11 4:17 AM
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.
2025-06-11 5:51 AM
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 */
2025-06-11 6:03 AM
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.
2025-06-11 6:59 AM
what you mean by going-on on the bus. and 8 is the value of local variable uint8_t check; if i declarer it as globule variable value showing "0".
2025-06-11 7:10 AM - edited 2025-06-11 7:11 AM
@Piyoosh wrote:
what you mean by going-on on the bus.
You need to check what happens on the I2C bus by probing SDA/SDL lines using a logic analyzer. This is the efficient way to debug the issue.
@Piyoosh wrote:
if i declarer it as globule variable value showing "0".
As the following?:
/* USER CODE BEGIN PV */
uint8_t check;
/* USER CODE END PV */
/* USER CODE END Header_StartDefaultTask */
void StartDefaultTask(void const * argument)
{
/* 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 */
}
Try also to decrease the optimization of the compiler.
What if you call :
HAL_I2C_Mem_Read(&hi2c1, (0x69 << 1), 0x00, 1, &check,1, 100);
before calling StartDefaultTask()?
But again you need to probe the SDA/SCL lines and see if you see that magic value "234" when reading the sensor.
2025-06-11 7:15 AM
@Piyoosh wrote:what you mean by going-on on the bus.
It means what is occurring on the physical wires - SDA and SCL - of the bus connections.
The datasheet for the the IMU will tell you what should be happening.
You have a working case (without RTOS) and a working one (with RTOS).
So observe the signals on the wires in both cases, and see where they differ - and compare to the requirements shown in the IMU datasheet.
This should lead you to why one of them works, while the other doesn't.
2025-06-12 12:55 AM - edited 2025-06-12 12:58 AM
I am using logic analyzer and finding this graph that is non rots project MX_I2C1_Init(); initialize successfully in first image but with RTOS project MX_I2C1_Init(); not initialized (graph showing in 2nd image with dark theme). Now what should i do because connection is same for both project. i2c is by default configured in rots also. Is there any specific config please mentioned.
2025-06-12 1:11 AM
So this is the working one, without RTOS:
Yes?
You've only shown the very start here - you need to show the complete transaction.
And this is the non-working one, with RTOS:
Yes?
In that one, I don't see anything happening at all ?
Clearly, if nothing is happening on the I2C bus lines, then there is no communication!