Migrate STM32F4 Firmware to FreeRTOS with I2C and PWM: A Step-by-Step Guide

Introduction

This tutorial will guide you through the process of migrating your STM32F4 bare-metal firmware to FreeRTOS, while integrating I2C and PWM functionalities. We will cover the necessary prerequisites, tools, and detailed steps to achieve a successful migration.

Prerequisites

• Basic knowledge of C programming and embedded systems.
• Familiarity with STM32 microcontrollers and their peripherals.
• STM32 development environment set up (e.g., STM32CubeIDE or Keil).
• FreeRTOS source code downloaded.

Parts/Tools

• STM32F4 microcontroller board.
• USB to UART converter (for debugging, if necessary).
• Development IDE (STM32CubeIDE or equivalent).
• FreeRTOS kernel files.

Steps

1. Set up the FreeRTOS project in the IDE:
   1. Create a new STM32 project in STM32CubeIDE.
   2. Go to the “Middleware” section and select FreeRTOS.
   3. Configure the FreeRTOS settings (e.g., stack size, priority).
2. Integrate your existing bare-metal firmware:
   1. Copy your existing source files into the new FreeRTOS project directory.
   2. Modify the linker script if necessary, to accommodate FreeRTOS.
   3. Update the main function to start the FreeRTOS scheduler:

   
   int main(void) {
       // System Initialization
       HAL_Init();
       SystemClock_Config();
       
       // Create tasks here
       xTaskCreate(Task1_Handler, "Task1", 100, NULL, 1, NULL);
       
       // Start the scheduler
       vTaskStartScheduler();
       
       while(1);
   }
               

3. Implement I2C communication:
   1. Enable I2C peripheral in STM32CubeMX.
   2. Generate the initialization code.
   3. Create an I2C task to handle communication:

   
   void I2C_Task(void *pvParameters) {
       uint8_t data[10];
       HAL_I2C_Master_Receive(&hi2c1, DEVICE_ADDRESS, data, sizeof(data), HAL_MAX_DELAY);
       // Process data
       vTaskDelay(pdMS_TO_TICKS(100));
   }
               

4. Implement PWM functionality:
   1. Enable the PWM timer in STM32CubeMX.
   2. Generate the required PWM code.
   3. Create a PWM task to control the output:

   
   void PWM_Task(void *pvParameters) {
       while (1) {
           __HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_1, 50); // 50% duty cycle
           vTaskDelay(pdMS_TO_TICKS(500));
       }
   }
               

5. Compile and debug the project:
   1. Build the project in the IDE.
   2. Connect the STM32 board to your computer.
   3. Use a debugger to upload the firmware to the microcontroller.
   4. Monitor the output via UART or debugger for any issues.

Troubleshooting

• Task not starting:

  Ensure that the stack size is adequate and that the task priorities do not conflict.

• I2C communication fails:

  Check your wiring and verify that the I2C address is correct. Use an oscilloscope to check signal integrity.

• PWM signal not as expected:

  Verify timer settings and ensure that the PWM signal is being updated correctly in the task.

Conclusion

In this tutorial, you successfully migrated your STM32F4 bare-metal firmware to FreeRTOS while integrating I2C and PWM functionalities. By following the outlined steps, you should now have a solid foundation for building more complex applications using FreeRTOS on your STM32 platform.