使用Platformio平台的libopencm3开发框架来开发STM32G0，下面为使用FreeRTOS系统。

1 新建项目

  • 在PIO主页新建项目，框架选择libopencm3，开发板选择 MonkeyPi_STM32_G070RB；
  • 新建完成后在src目录新建主程序文件main.c；
  • 然后更改项目文件platformio.ini的烧写和调试方式：
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upload_protocol = cmsis-dap
debug_tool = cmsis-dap

2 添加FreeRTOS源码

  • 下载FreeRTOS源码

在freertos网站：https://www.freertos.org/a00104.html 下载好源码，这里下载最新版202112.00；

  • 添加源码到项目：

直接拷贝源码下的FreeRTOS文件夹到项目的lib目录中；

  • 添加到项目编译

在lib目录的FreeRTOS文件夹下新建 library.json 文件，内容如下：

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{
    "name": "FreeRTOS",
    "version": "202112.00",
    "build": {
        "flags": [
            "-Isource",
            "-Isource/include",
            "-Isource/portable/GCC/ARM_CM0",
            "-Isource/portable/RVDS/ARM_CM0"
        ],
        "srcFilter": [
            "+<source/*.c>",
            "+<source/portable/GCC/ARM_CM0/*.c>",
            "+<source/portable/MemMang/heap_4.c>"
        ]
    }
}
  • 添加FreeRTOS配置

从FreeRTOS源码下的demo目录中拷贝一个FreeRTOSConfig.h文件到 lib/FreeRTOS/Source目录，并更改为如下内容：

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/**
 * @file FreeRTOSConfig.h
 * 
 * http://www.FreeRTOS.org
 * http://aws.amazon.com/freertos
 * 
 */

#ifndef FREERTOS_CONFIG_H
#define FREERTOS_CONFIG_H

/*-----------------------------------------------------------
 * Application specific definitions.
 *
 * These definitions should be adjusted for your particular hardware and
 * application requirements.
 *
 * These parameters and more are described within the 'configuration' section of the
 * FreeRTOS API documentation available on the FreeRTOS.org web site.
 *
 * See http://www.freertos.org/a00110.html
 *----------------------------------------------------------*/

/* USER CODE BEGIN Includes */
/* Section where include file can be added */
/* USER CODE END Includes */

/* Ensure definitions are only used by the compiler, and not by the assembler. */
#if defined(__ICCARM__) || defined(__CC_ARM) || defined(__GNUC__)
  #include <stdint.h>
#endif
#define configENABLE_FPU                         0
#define configENABLE_MPU                         0

#define configUSE_PREEMPTION                     1
#define configSUPPORT_STATIC_ALLOCATION          0
#define configSUPPORT_DYNAMIC_ALLOCATION         1
#define configUSE_IDLE_HOOK                      0
#define configUSE_TICK_HOOK                      0
#define configCPU_CLOCK_HZ						 ( ( unsigned long ) 64000000 )	
#define configTICK_RATE_HZ                       ((TickType_t)1000)
#define configMAX_PRIORITIES                     ( 7 )
#define configMINIMAL_STACK_SIZE                 ((uint16_t)256)
#define configTOTAL_HEAP_SIZE                    ((size_t)1024*16)
#define configMAX_TASK_NAME_LEN                  ( 16 )
#define configUSE_16_BIT_TICKS                   0
#define configUSE_MUTEXES                        1
#define configQUEUE_REGISTRY_SIZE                8
#define configUSE_PORT_OPTIMISED_TASK_SELECTION  0

/*Software timer related definitions. */
#define configUSE_TIMERS                        1
#define configTIMER_TASK_PRIORITY               5
#define configTIMER_QUEUE_LENGTH                10
#define configTIMER_TASK_STACK_DEPTH            configMINIMAL_STACK_SIZE

/* USER CODE BEGIN MESSAGE_BUFFER_LENGTH_TYPE */
/* Defaults to size_t for backward compatibility, but can be changed
   if lengths will always be less than the number of bytes in a size_t. */
#define configMESSAGE_BUFFER_LENGTH_TYPE         size_t
/* USER CODE END MESSAGE_BUFFER_LENGTH_TYPE */

/* Co-routine definitions. */
#define configUSE_CO_ROUTINES                    0
#define configMAX_CO_ROUTINE_PRIORITIES          ( 2 )

/* Set the following definitions to 1 to include the API function, or zero
to exclude the API function. */
#define INCLUDE_vTaskPrioritySet             1
#define INCLUDE_uxTaskPriorityGet            1
#define INCLUDE_vTaskDelete                  1
#define INCLUDE_vTaskCleanUpResources        0
#define INCLUDE_vTaskSuspend                 1
#define INCLUDE_vTaskDelayUntil              0
#define INCLUDE_vTaskDelay                   1
#define INCLUDE_xTaskGetSchedulerState       1

/* Normal assert() semantics without relying on the provision of an assert.h
header file. */
/* USER CODE BEGIN 1 */
//void vAssertCalled(const char *file, int line);
//#define configASSERT( x )       if( x == 0 ) { taskDISABLE_INTERRUPTS(); vAssertCalled(__FILE__,__LINE__); for(;;); }
/* USER CODE END 1 */

/* Definitions that map the FreeRTOS port interrupt handlers to their CMSIS
standard names. */
#define vPortSVCHandler    sv_call_handler
#define xPortPendSVHandler pend_sv_handler

/* IMPORTANT: This define is commented when used with STM32Cube firmware, when the timebase source is SysTick,
              to prevent overwriting SysTick_Handler defined within STM32Cube HAL */

#define xPortSysTickHandler sys_tick_handler

/* USER CODE BEGIN Defines */
/* Section where parameter definitions can be added (for instance, to override default ones in FreeRTOS.h) */
/* USER CODE END Defines */

#endif /* FREERTOS_CONFIG_H */

上面配置需要根据自己的需要进行更改，如CPU频率，是否需要打开某项功能等；

  • 配置好后的目录结构如下：

3 FreeRTOS示例

  • 首先需要设置FreeRTOS需要的时钟
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/**
 * @brief systick setup for rtos tick
 */
static void systick_setup(void)
{
	systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
	systick_set_reload(64*1000);

	systick_interrupt_enable();

	/* Start counting. */
	systick_counter_enable();
}

这样在FreeRTOSConfig.h 文件中定义的

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#define xPortSysTickHandler sys_tick_handler

就可以通过systick中断提供FreeRTOS时钟；

  • LED任务函数
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static void led1_task(void *args)
{
    rcc_periph_clock_enable(RCC_GPIOC);
    gpio_mode_setup(GPIOC,GPIO_MODE_OUTPUT,GPIO_PUPD_NONE,GPIO12);
    
    while (1)
    {
        gpio_toggle(GPIOC,GPIO12);
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}
  • 主程序中创建任务并开启多任务调度
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#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/cm3/systick.h>

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


int main(void)
{
    //system clock
    rcc_clock_setup(&rcc_clock_config[RCC_CLOCK_CONFIG_HSI_PLL_64MHZ]);

    systick_setup();

    xTaskCreate(led_task,"led task", 256, NULL,2,NULL);

    vTaskStartScheduler();
    
    while(1){}

    return 0;
}

通过xTaskCreate创建多任务函数，然后使用 vTaskStartScheduler 开始调度；

注：如果VSCode中提示 FreeRTOS.h 头文件include path问题，可以将项目文件夹关闭，再重新打开即可；如果是在Clion中，可以在添加lib文件夹后，右键platformio.ini文件选择re init即可；

4 烧写测试

点击 PlatformIO：Upload按钮或Ctrl+Alt+U快捷键可以直接编译烧写到目标板，看到LED按预定的程序闪烁运行；