ARM Cortex-M3 (STM32F103) Tutorial - FreeRTOS - Task

In this tutorial, I will share how use an RTOS on STM32F103 microcontroller. I use FreeRTOS for this tutorial. RTOS is usually needs when an embedded system must responds to an event within a strictly defined time.

In this tutorial, I will make RTOS task with 3 LED that blinks at different frequency. First thing to do is to download FreeRTOS library. The next step is to make a new project in Keil uVision and setup the configuration for using FreeRTOS on STM32F103.

You have to make a new project on Keil uVision for STM32F103. If you don't know how to make a new project, you can view this tutorial. Follow this steps below to setup the configuration for using FreeRTOS.

• Add FreeRTOS source library to your project folder. That library file is separated within a folder called FreeRTOS. In that folder is consist of these file:

• Copy FreeRTOSConfig.h file from FreeRTOS demo file for STM32F103 using Keil (in folder CORTEX_STM32F103_Keil) to folder FreeRTOS\include in your project.
• Not all files in the portable folder is needed, you only need MemMang folder and RVDS\ARM_CM3 folder. The ARM_CM3 folder contains SysTick definitions for STM32F103 microcontroller.
• In the project explorer, add these FreeRTOS source code:

 

• Go to the Include Paths settings in the Options for Target dialog and add paths to the FreeRTOS header file:

• Open FreeRTOSConfig.h file, then add this code for map map the FreeRTOS port interrupt handlers to the CMSIS standard names:

/* Definitions that map the FreeRTOS port interrupt handlers to their CMSIS
standard names. */
#define vPortSVCHandler SVC_Handler
#define xPortPendSVHandler PendSV_Handler
#define xPortSysTickHandler SysTick_Handler

Until this step, now we are ready to make application using FreeRTOS. This is the full code for LED blinking using FreeRTOS:

#include "stm32f10x.h"
#include "stm32f10x_rcc.h"
#include "stm32f10x_gpio.h"

#include "FreeRTOS/include/FreeRTOS.h"
#include "FreeRTOS/include/task.h"

void ledInit(void);
// RTOS task
void vTaskLedRed(void *p);
void vTaskLedYellow(void *p);
void vTaskLedGreen(void *p);

int main(void)
{
    // Configure GPIO for LED
    ledInit();

    // Create LED blink task
    xTaskCreate(vTaskLedRed, (const char*) "Red LED Blink", 
        128, NULL, 1, NULL);
    xTaskCreate(vTaskLedYellow, (const char*) "Yellow LED Blink",
        128, NULL, 1, NULL);
    xTaskCreate(vTaskLedGreen, (const char*) "Green LED Blink",
        128, NULL, 1, NULL);
    // Start RTOS scheduler
    vTaskStartScheduler();

    return 0;
}

void ledInit()
{
    GPIO_InitTypeDef GPIO_InitStruct;

    // Configure PC13, PC14, PC15 as push-pull output
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_2MHz;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(GPIOC, &GPIO_InitStruct);
}

void vTaskLedRed(void *p)
{
    for (;;)
    {
        GPIOC->ODR ^= GPIO_Pin_14;
        vTaskDelay(100/portTICK_RATE_MS);
    }
}

void vTaskLedYellow(void *p)
{
    for (;;)
    {
        GPIOC->ODR ^= GPIO_Pin_15;
        vTaskDelay(500/portTICK_RATE_MS);
    }
}

void vTaskLedGreen(void *p)
{
    for (;;)
    {
        GPIOC->ODR ^= GPIO_Pin_13;
        vTaskDelay(1000/portTICK_RATE_MS);
    }
}

You can also see this code on my repository.