How to Implement and Debug FreeRTOS Task Scheduler on STM32F4

Implementing and Debugging a FreeRTOS Task Scheduler on STM32F4 Microcontroller with a Custom Interrupt-Driven Timer

This tutorial provides a step-by-step guide to implementing and debugging a FreeRTOS task scheduler on the STM32F4 microcontroller using a custom interrupt-driven timer. By the end of this tutorial, you will have a basic understanding of setting up FreeRTOS and how to use a timer for task scheduling.

Prerequisites

• Basic knowledge of C programming
• Familiarity with STM32F4 microcontroller
• STM32 development environment (e.g., STM32CubeIDE)
• FreeRTOS library files
• Basic understanding of interrupt handling

Parts/Tools

• STM32F4 development board
• USB to UART adapter (if necessary for debugging)
• JTAG/SWD programmer (such as ST-LINK)
• FreeRTOS library
• STM32CubeMX (optional for configuration)

Steps

1. Set up the FreeRTOS environment:
   1. Download FreeRTOS from the official website.
   2. Include the FreeRTOS source files in your STM32CubeIDE project.
   3. Configure FreeRTOS settings in FreeRTOSConfig.h file.
2. Configure the STM32F4 Timer:
   1. Open STM32CubeMX and create a new project for your STM32F4 board.
   2. Enable the timer peripheral (e.g., TIM2).
   3. Set the timer to interrupt mode with an appropriate frequency.
   4. Generate the code and open it in STM32CubeIDE.
3. Implement the Timer Interrupt Handler:
   1. In the generated code, locate the timer interrupt handler function (e.g., TIM2_IRQHandler()).
   2. In the handler, call the FreeRTOS tick function:

   
   void TIM2_IRQHandler(void) {
       HAL_TIM_IRQHandler(&htim2);
       xPortSysTickHandler(); // Call the FreeRTOS tick handler
   }
               

4. Create FreeRTOS Tasks:
   1. Define your tasks in a new source file:

   
   void vTask1(void *pvParameters) {
       while(1) {
           // Task code here
       }
   }
               

   2. In the main function, create the tasks:

   
   xTaskCreate(vTask1, "Task 1", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
   vTaskStartScheduler(); // Start the scheduler
               

5. Debugging the Application:
   1. Build the project and upload it to the STM32F4 board.
   2. Set breakpoints in your tasks and the timer interrupt handler.
   3. Use the debugger to step through the code and monitor task execution.

Troubleshooting

• Task not executing: Ensure the task is created and the scheduler is started. Check priorities and stack size.
• Interrupt not triggering: Verify timer configuration in STM32CubeMX and ensure the correct timer is enabled in the code.
• FreeRTOS not responding: Check for stack overflows or watchdog timer resets. Increase stack size or adjust priorities if necessary.

Conclusion

In this tutorial, you successfully implemented a FreeRTOS task scheduler on the STM32F4 microcontroller using a custom interrupt-driven timer. By following these steps, you should now have a basic operational setup that can be expanded with additional tasks and functionalities. Don’t hesitate to explore more advanced FreeRTOS features to enhance your embedded applications.