1. GD32F427和RTOS下载
FreeRTOS作为使用量比较多的实时系统，在小车控制、IOT领域都比较常见，而且由于开源免费，相对于其他系统，有更大的发展。在GDF4上移植，首先是下载RTOS内核，官网网站：https://www.freertos.org/a00104.html。
我使用的是LTS长期支持版，也会比较稳定，下载之后的文件中包含多个文件，涉及到MQTT协议、HTTP等，用于物联网场景，我只需要RTOSKernel的文件内容。
kernel目录下包含源文件、头文件和Portable，源文件主要添加的文件如图所示。
其中heap_4.c在FreeRTOS_Kernel\portable\MemMang文件夹下，port.c在\FreeRTOS\Source\portable\RVDS\ARM_CM4F文件夹下,heap4是常用的内存管理设计，具体内容看手册。在添加完所需的源文件之后，就是keil中添加os的头文件，头文件的路径分别在FreeRTOS_Kernel\include，FreeRTOS_Kernel\portable\RVDS\ARM_CM4F,这样编译之后还会显示不通过，是因为缺少FreeRTOSConfig.h文件，可以自己编写，也可以从FreeRTOS的demo中复制添加，我把我用的配置文件放在下面。
/** FreeRTOS Kernel V10.0.1 Copyright (C) 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
* http://www.FreeRTOS.org
* http://aws.amazon.com/freertos
* 1 tab == 4 spaces!
*/
#ifndef FREERTOS_CONFIG_H
#define FREERTOS_CONFIG_H
#if defined(__CC_ARM) || defined(__ICCARM__)
#include <stdint.h>
extern uint32_t SystemCoreClock;
#endif
#define configUSE_PREEMPTION 1
#define configCPU_CLOCK_HZ ( SystemCoreClock )
#define configTICK_RATE_HZ ( ( TickType_t ) 1000 )
#define configMAX_PRIORITIES ( 8 )
#define configMINIMAL_STACK_SIZE ( ( unsigned short ) 130 )
#define configTOTAL_HEAP_SIZE ( ( size_t ) ( 16 * 1024 ) )
#define configMAX_TASK_NAME_LEN ( 16 )
#define configUSE_16_BIT_TICKS 0
#define configIDLE_SHOULD_YIELD 1
#define configUSE_MUTEXES 1
#define configUSE_RECURSIVE_MUTEXES 1
#define configUSE_COUNTING_SEMAPHORES 1
#define configQUEUE_REGISTRY_SIZE 8
#define configUSE_QUEUE_SETS 0
#define configUSE_APPLICATION_TASK_TAG 0
/* hook function related definitions Èç¹ûÊÇ1£¬¸Ä³É0*/
#define configUSE_IDLE_HOOK 0
#define configUSE_TICK_HOOK 0
#define configCHECK_FOR_STACK_OVERFLOW 0
#define configUSE_MALLOC_FAILED_HOOK 0
#define configSUPPORT_STATIC_ALLOCATION 0
#define configUSE_TICKLESS_IDLE 0
#define configNUM_THREAD_LOCAL_STORAGE_POINTERS 0
#define configUSE_TRACE_FACILITY 1
/* This demo makes use of one or more example stats formatting functions. These
format the raw data provided by the uxTaskGetSystemState() function in to human
readable ASCII form. See the notes in the implementation of vTaskList() within
FreeRTOS/Source/tasks.c for limitations. */
#define configUSE_STATS_FORMATTING_FUNCTIONS 0
/* Run time stats gathering definitions. */
#define configGENERATE_RUN_TIME_STATS 0
#define portCONFIGURE_TIMER_FOR_RUN_TIME_STATS()
#define portGET_RUN_TIME_COUNTER_VALUE() 0
/* co-routine definitions */
#define configUSE_CO_ROUTINES 0
#define configMAX_CO_ROUTINE_PRIORITIES ( 2 )
/* software timer definitions */
#define configUSE_TIMERS 0
#define configTIMER_TASK_PRIORITY ( 2 )
#define configTIMER_QUEUE_LENGTH 10
#define configTIMER_TASK_STACK_DEPTH ( configMINIMAL_STACK_SIZE * 2 )
/* set to 1 to include the API function, or 0 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 1
#define INCLUDE_vTaskDelay 1
#define INCLUDE_eTaskGetState 1
#define INCLUDE_xTimerPendFunctionCall 0
#define INCLUDE_xSemaphoreGetMutexHolder 0
#define INCLUDE_xTaskGetHandle 1
#define INCLUDE_xTaskGetCurrentTaskHandle 1
#define INCLUDE_xTaskGetIdleTaskHandle 0
#define INCLUDE_xTaskAbortDelay 0
#define INCLUDE_xTaskGetSchedulerState 1
#define INCLUDE_uxTaskGetStackHighWaterMark 1
/* Cortex-M specific definitions */
#ifdef __NVIC_PRIO_BITS
/* __NVIC_PRIO_BITS will be specified when CMSIS is being used. */
#define configPRIO_BITS __NVIC_PRIO_BITS
#else
#define configPRIO_BITS 4 /* 15 priority levels */
#endif
/* the lowest interrupt priority that can be used in a call to a "set priority" function */
#define configLIBRARY_LOWEST_INTERRUPT_PRIORITY 0xf
/* The highest interrupt priority that can be used by any interrupt service
routine that makes calls to interrupt safe FreeRTOS API functions. Do not call
interrupt safe freertos api functions from any interrupt that has a higher
priority than this! (higher priorities are lower numeric values. */
#define configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY 2
/* interrupt priorities used by the kernel port layer itself */
#define configKERNEL_INTERRUPT_PRIORITY ( configLIBRARY_LOWEST_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )
/* configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to zero */
#define configMAX_SYSCALL_INTERRUPT_PRIORITY ( configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )
/* normal assert() semantics without relying on the provision of an assert.h header file */
#define configASSERT( x ) if( ( x ) == 0 ) { taskDISABLE_INTERRUPTS(); for( ;; ); }
/* map the FreeRTOS port interrupt handlers to CMSIS standard names */
#define vPortSVCHandler SVC_Handler
#define xPortPendSVHandler PendSV_Handler
#define xPortSysTickHandler SysTick_Handler
#endif /* FREERTOS_CONFIG_H */移植到这，差不多就可以了，编译一下，还有三个问题，重复定义的问题，关于void PendSV_Handler(void)、void SysTick_Handler(void)、void SVC_Handler(void)三个中断处理有重复定义，我是把gd32f4xx_it.c中的文件屏蔽掉，留下FreeRTOS中定义的几个函数。到此为止，基本移植就完成了，接下来创建几个任务试试。
2. 任务创建
之后任务创建就是调用task.c里面的函数
BaseType_t xTaskCreate( TaskFunction_t pxTaskCode,
const char * const pcName,
const configSTACK_DEPTH_TYPE usStackDepth,
void * const pvParameters,
UBaseType_t uxPriority,
TaskHandle_t * const pxCreatedTask )每创建一个任务，会分配两块内存区，用于任务控制块和stack区，任务采用抢占式调度。我把BSP相关的外设初始化放在一个BSP_Init函数中，任务函数则放在System文件夹下，目前设计了datatxrx.c，用于数据接收。设计后的目录结构和任务。目前是编译通过了，具体的细节还在设计，下次整理一下rtos的手册和接收数据任务、存数据任务的调度再写一写。
