使用Platformio平臺的libopencm3開發框架來開發STM32G0，下面為使用FreeRTOS系統。

1 新建項目

• 在PIO主頁新建項目，框架選擇libopencm3，開發板選擇 MonkeyPi_STM32_G070RB；
• 新建完成后在src目錄新建主程序文件main.c；
• 然后更改項目文件platformio.ini的燒寫和調試方式：

1upload_protocol = cmsis-dap
2debug_tool = cmsis-dap

2 添加FreeRTOS源碼

• 下載FreeRTOS源碼

在freertos網站：https://www.freertos.org/a00104.html 下載好源碼，這里下載最新版202112.00；

• 添加源碼到項目：

直接拷貝源碼下的FreeRTOS文件夾到項目的lib目錄中；

• 添加到項目編譯

在lib目錄的FreeRTOS文件夾下新建 library.json 文件，內容如下：

1{
 2    "name": "FreeRTOS",
 3    "version": "202112.00",
 4    "build": {
 5        "flags": [
 6            "-Isource",
 7            "-Isource/include",
 8            "-Isource/portable/GCC/ARM_CM0",
 9            "-Isource/portable/RVDS/ARM_CM0"
10        ],
11        "srcFilter": [
12            "+",
13            "+",
14            "+"
15        ]
16    }
17}

• 添加FreeRTOS配置

從FreeRTOS源碼下的demo目錄中拷貝一個FreeRTOSConfig.h文件到 lib/FreeRTOS/Source目錄，并更改為如下內容：

1/**
 2 * @file FreeRTOSConfig.h
 3 * 
 4 * http://www.FreeRTOS.org
 5 * http://aws.amazon.com/freertos
 6 * 
 7 */
 8
 9#ifndef FREERTOS_CONFIG_H
10#define FREERTOS_CONFIG_H
11
12/*-----------------------------------------------------------
13 * Application specific definitions.
14 *
15 * These definitions should be adjusted for your particular hardware and
16 * application requirements.
17 *
18 * These parameters and more are described within the 'configuration' section of the
19 * FreeRTOS API documentation available on the FreeRTOS.org web site.
20 *
21 * See http://www.freertos.org/a00110.html
22 *----------------------------------------------------------*/
23
24/* USER CODE BEGIN Includes */
25/* Section where include file can be added */
26/* USER CODE END Includes */
27
28/* Ensure definitions are only used by the compiler, and not by the assembler. */
29#if defined(__ICCARM__) || defined(__CC_ARM) || defined(__GNUC__)
30  #include 
31#endif
32#define configENABLE_FPU                         0
33#define configENABLE_MPU                         0
34
35#define configUSE_PREEMPTION                     1
36#define configSUPPORT_STATIC_ALLOCATION          0
37#define configSUPPORT_DYNAMIC_ALLOCATION         1
38#define configUSE_IDLE_HOOK                      0
39#define configUSE_TICK_HOOK                      0
40#define configCPU_CLOCK_HZ                         ( ( unsigned long ) 64000000 ) 
41#define configTICK_RATE_HZ                       ((TickType_t)1000)
42#define configMAX_PRIORITIES                     ( 7 )
43#define configMINIMAL_STACK_SIZE                 ((uint16_t)256)
44#define configTOTAL_HEAP_SIZE                    ((size_t)1024*16)
45#define configMAX_TASK_NAME_LEN                  ( 16 )
46#define configUSE_16_BIT_TICKS                   0
47#define configUSE_MUTEXES                        1
48#define configQUEUE_REGISTRY_SIZE                8
49#define configUSE_PORT_OPTIMISED_TASK_SELECTION  0
50
51/*Software timer related definitions. */
52#define configUSE_TIMERS                        1
53#define configTIMER_TASK_PRIORITY               5
54#define configTIMER_QUEUE_LENGTH                10
55#define configTIMER_TASK_STACK_DEPTH            configMINIMAL_STACK_SIZE
56
57/* USER CODE BEGIN MESSAGE_BUFFER_LENGTH_TYPE */
58/* Defaults to size_t for backward compatibility, but can be changed
59   if lengths will always be less than the number of bytes in a size_t. */
60#define configMESSAGE_BUFFER_LENGTH_TYPE         size_t
61/* USER CODE END MESSAGE_BUFFER_LENGTH_TYPE */
62
63/* Co-routine definitions. */
64#define configUSE_CO_ROUTINES                    0
65#define configMAX_CO_ROUTINE_PRIORITIES          ( 2 )
66
67/* Set the following definitions to 1 to include the API function, or zero
68to exclude the API function. */
69#define INCLUDE_vTaskPrioritySet             1
70#define INCLUDE_uxTaskPriorityGet            1
71#define INCLUDE_vTaskDelete                  1
72#define INCLUDE_vTaskCleanUpResources        0
73#define INCLUDE_vTaskSuspend                 1
74#define INCLUDE_vTaskDelayUntil              0
75#define INCLUDE_vTaskDelay                   1
76#define INCLUDE_xTaskGetSchedulerState       1
77
78/* Normal assert() semantics without relying on the provision of an assert.h
79header file. */
80/* USER CODE BEGIN 1 */
81//void vAssertCalled(const char *file, int line);
82//#define configASSERT( x )       if( x == 0 ) { taskDISABLE_INTERRUPTS(); vAssertCalled(__FILE__,__LINE__); for(;;); }
83/* USER CODE END 1 */
84
85/* Definitions that map the FreeRTOS port interrupt handlers to their CMSIS
86standard names. */
87#define vPortSVCHandler    sv_call_handler
88#define xPortPendSVHandler pend_sv_handler
89
90/* IMPORTANT: This define is commented when used with STM32Cube firmware, when the timebase source is SysTick,
91              to prevent overwriting SysTick_Handler defined within STM32Cube HAL */
92
93#define xPortSysTickHandler sys_tick_handler
94
95/* USER CODE BEGIN Defines */
96/* Section where parameter definitions can be added (for instance, to override default ones in FreeRTOS.h) */
97/* USER CODE END Defines */
98
99#endif /* FREERTOS_CONFIG_H */

上面配置需要根據自己的需要進行更改，如CPU頻率，是否需要打開某項功能等；

• 配置好后的目錄結構如下：

image-20220910154501074

3 FreeRTOS示例

• 首先需要設置FreeRTOS需要的時鐘

1/**
 2 * @brief systick setup for rtos tick
 3 */
 4static void systick_setup(void)
 5{
 6    systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
 7    systick_set_reload(64*1000);
 8
 9    systick_interrupt_enable();
10
11    /* Start counting. */
12    systick_counter_enable();
13}

這樣在FreeRTOSConfig.h 文件中定義的

1#define xPortSysTickHandler sys_tick_handler

就可以通過systick中斷提供FreeRTOS時鐘；

• LED任務函數

1static void led1_task(void *args)
 2{
 3    rcc_periph_clock_enable(RCC_GPIOC);
 4    gpio_mode_setup(GPIOC,GPIO_MODE_OUTPUT,GPIO_PUPD_NONE,GPIO12);
 5
 6    while (1)
 7    {
 8        gpio_toggle(GPIOC,GPIO12);
 9        vTaskDelay(pdMS_TO_TICKS(500));
10    }
11}

• 主程序中創建任務并開啟多任務調度

1#include 
 2#include 
 3#include 
 4
 5#include "FreeRTOS.h"
 6#include "task.h"
 7
 8
 9int main(void)
10{
11    //system clock
12    rcc_clock_setup(&rcc_clock_config[RCC_CLOCK_CONFIG_HSI_PLL_64MHZ]);
13
14    systick_setup();
15
16    xTaskCreate(led_task,"led task", 256, NULL,2,NULL);
17
18    vTaskStartScheduler();
19
20    while(1){}
21
22    return 0;
23}

通過xTaskCreate創建多任務函數，然后使用 vTaskStartScheduler 開始調度；

注：如果VSCode中提示 FreeRTOS.h 頭文件include path問題，可以將項目文件夾關閉，再重新打開即可；如果是在Clion中，可以在添加lib文件夾后，右鍵platformio.ini文件選擇re init即可；

4 燒寫測試

點擊 PlatformIO：Upload按鈕或Ctrl+Alt+U快捷鍵可以直接編譯燒寫到目標板，看到LED按預定的程序閃爍運行。