1. Introduction

FreeRTOS is a tailorable, deprived multitasking kernel, and there is no limit on the number of tasks. FreeRTOS provides all the functions required by a real-time operating system, including resource management, synchronization, and task communication.

FreeRTOS is written in C and assembly, most of which are written in C language, and only a very small part of the code closely related to the processor is written in assembly. FreeRTOS has a simple structure and is very readable. ! The most important thing is that it is very suitable for students who are new to embedded real-time operating systems, embedded system developers and enthusiasts to learn.

The latest version V9.0.0 (2016), although the version of FreeRTOS has been updated to V10.4.1, we still choose V9.0.0 because the kernel is stable and there are a lot of online information, because the V10.0.0 version was acquired by Amazon The version that came out after FreeRTOS mainly added some cloud components, and V9.0.0 is generally sufficient.

FreeRTOS ：网：http://www.freertos.org/
Code hosting website: https://sourceforge.net/projects/freertos/files/FreeRTOS/

Second, the directory structure

FreeRTOS includes:

Demo example
Source kernel source code

Source contains:

include general header files
portable universal C file
croutine coroutine
list list
queue
tasks
timers software timer

portable includes:

Keil Same RVDS
MemMang memory management
RVDS

MemMang contains:

5 heap files

You must use one of them when porting, because FreeRTOS uses dynamic memory allocation when creating objects, and these dynamic memory allocation functions are implemented in these files. Different allocation algorithms lead to different efficiency and results. Generally Used heap4.c.

RVDS includes:

Cortex-M0, M3, M4, M7 and other core MCU interface files
port.c interface file
portmacro.h header file, mainly some data types and macro definitions

Three, the transplantation process

3.1 Extract the simplest source code

First, create a new folder in the root directory of the STM32 bare metal project and name it FreeRTOS
Then in the FreeRTOSfolder under a new three empty folders, include, port,src
Open source FreeRTOS V9.0.0 find all the '.c file' in "FreeRTOSv9.0.0 \ FreeRTOS \ Source" directory, we will copy them to the new srcfolder
Open source FreeRTOS V9.0.0, the "FreeRTOSv9.0.0 \ FreeRTOS \ Source \ portable " Head
Found "MemMang" folder and "RVDS" folder, copy them to us at the new record portfolder
FreeRTOS V9.0.0 open source, find "include" folder under "FreeRTOSv9.0.0 \ FreeRTOS \ Source" directory, which is that we need to use some FreeRTOS header files, and copy it directly to our new includefolder

3.2 Copy FreeRTOSConfig.h file to User folder

FreeRTOSConfig.h The file is the engineering configuration file of FreeRTOS. Because FreeRTOS is a real-time operating kernel that can be tailored, it is applied to different processor platforms. Users can tailor the functionality of FreeRTOS by modifying the configuration header file of the FreeRTOS kernel, so we copy it Put it under the User folder.

Open the FreeRTOSv9.0.0 source code, find the "CORTEX_STM32F103_Keil" folder under the "FreeRTOSv9.0.0\FreeRTOS\Demo" folder, find the "FreeRTOSConfig.h" file in its root directory, and copy it to the User folder of our project Just down

3.3 Add source code to the project group folder

Next we create in mdk inside FreeRTOS/srcand FreeRTOS/porttwo group folders, which FreeRTOS/srcused to store the contents of the src folder FreeRTOS/portfor storing port \ MemMang folder with the port \ RVDS content \ ARM_CM3 folder.
Then we add the content of FreeRTOS in the project file to the project, and add our FreeRTOS project source code according to the newly created group.

In the FreeRTOS/portAdd folder MemMang file packets can simply select one, we choose "heap_4.c", which is a memory management FreeRTOS source code file.

Then add our FreeRTOS configuration file "FreeRTOSConfig.h" in the User group

3.4 Specify the header file path

The source code of FreeRTOS has been added to the group folder of the development environment. When compiling, you need to specify the path of the header file for these source files, otherwise the compilation will report an error. In the source code of FreeRTOS, only FreeRTOS\include and FreeRTOS\port\RVDS\ARM_CM3 have header files under these two folders. You only need to specify the path of these two header files in the development environment. At the same time, we also copied the FreeRTOSConfig.h header file to the User folder under the project root directory, so the User path should also be added to the development environment.

3.5 Modify FreeRTOSConfig.h

FreeRTOSConfig.h is directly copied from the demo folder. This header file defines the macros needed to tailor the entire FreeRTOS function. Some macro definitions are enabled and some macro definitions are disabled. At the beginning, we only The simplest function needs to be configured. To configure FreeRTOS functions as we want, we must have a grasp of the functions of these macro definitions. Below we briefly introduce the meaning of these macro definitions, and then modify these macro definitions.

/*
    FreeRTOS V9.0.0 - Copyright (C) 2016 Real Time Engineers Ltd.
    All rights reserved

    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

    This file is part of the FreeRTOS distribution.

    FreeRTOS is free software; you can redistribute it and/or modify it under
    the terms of the GNU General Public License (version 2) as published by the
    Free Software Foundation >>>> AND MODIFIED BY <<<< the FreeRTOS exception.

    ***************************************************************************
    >>!   NOTE: The modification to the GPL is included to allow you to     !<<
    >>!   distribute a combined work that includes FreeRTOS without being   !<<
    >>!   obliged to provide the source code for proprietary components     !<<
    >>!   outside of the FreeRTOS kernel.                                   !<<
    ***************************************************************************

    FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    FOR A PARTICULAR PURPOSE.  Full license text is available on the following
    link: http://www.freertos.org/a00114.html

    ***************************************************************************
     *                                                                       *
     *    FreeRTOS provides completely free yet professionally developed,    *
     *    robust, strictly quality controlled, supported, and cross          *
     *    platform software that is more than just the market leader, it     *
     *    is the industry's de facto standard.                               *
     *                                                                       *
     *    Help yourself get started quickly while simultaneously helping     *
     *    to support the FreeRTOS project by purchasing a FreeRTOS           *
     *    tutorial book, reference manual, or both:                          *
     *    http://www.FreeRTOS.org/Documentation                              *
     *                                                                       *
    ***************************************************************************

    http://www.FreeRTOS.org/FAQHelp.html - Having a problem?  Start by reading
    the FAQ page "My application does not run, what could be wrong?".  Have you
    defined configASSERT()?

    http://www.FreeRTOS.org/support - In return for receiving this top quality
    embedded software for free we request you assist our global community by
    participating in the support forum.

    http://www.FreeRTOS.org/training - Investing in training allows your team to
    be as productive as possible as early as possible.  Now you can receive
    FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
    Ltd, and the world's leading authority on the world's leading RTOS.

    http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
    including FreeRTOS+Trace - an indispensable productivity tool, a DOS
    compatible FAT file system, and our tiny thread aware UDP/IP stack.

    http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
    Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.

    http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
    Integrity Systems ltd. to sell under the OpenRTOS brand.  Low cost OpenRTOS
    licenses offer ticketed support, indemnification and commercial middleware.

    http://www.SafeRTOS.com - High Integrity Systems also provide a safety
    engineered and independently SIL3 certified version for use in safety and
    mission critical applications that require provable dependability.

*/


#ifndef FREERTOS_CONFIG_H
#define FREERTOS_CONFIG_H

#include "stm32f10x.h"
#include "bsp_usart.h"


//针对不同的编译器调用不同的stdint.h文件
#if defined(__ICCARM__) || defined(__CC_ARM) || defined(__GNUC__)
    #include <stdint.h>
    extern uint32_t SystemCoreClock;
#endif

//断言
#define vAssertCalled(char,int) printf("Error:%s,%d\r\n",char,int)
#define configASSERT(x) if((x)==0) vAssertCalled(__FILE__,__LINE__)

/************************************************************************
 *               FreeRTOS基础配置配置选项 
 *********************************************************************/
/* 置1：RTOS使用抢占式调度器；置0：RTOS使用协作式调度器（时间片）
 * 
 * 注：在多任务管理机制上，操作系统可以分为抢占式和协作式两种。
 * 协作式操作系统是任务主动释放CPU后，切换到下一个任务。
 * 任务切换的时机完全取决于正在运行的任务。
 */
#define configUSE_PREEMPTION                    1

//1使能时间片调度(默认式使能的)
#define configUSE_TIME_SLICING                  1		

/* 某些运行FreeRTOS的硬件有两种方法选择下一个要执行的任务：
 * 通用方法和特定于硬件的方法（以下简称“特殊方法”）。
 * 
 * 通用方法：
 *      1.configUSE_PORT_OPTIMISED_TASK_SELECTION 为 0 或者硬件不支持这种特殊方法。
 *      2.可以用于所有FreeRTOS支持的硬件
 *      3.完全用C实现，效率略低于特殊方法。
 *      4.不强制要求限制最大可用优先级数目
 * 特殊方法：
 *      1.必须将configUSE_PORT_OPTIMISED_TASK_SELECTION设置为1。
 *      2.依赖一个或多个特定架构的汇编指令（一般是类似计算前导零[CLZ]指令）。
 *      3.比通用方法更高效
 *      4.一般强制限定最大可用优先级数目为32
 * 一般是硬件计算前导零指令，如果所使用的，MCU没有这些硬件指令的话此宏应该设置为0！
 */
#define configUSE_PORT_OPTIMISED_TASK_SELECTION     1                       
                                                                        
/* 置1：使能低功耗tickless模式；置0：保持系统节拍（tick）中断一直运行
 * 假设开启低功耗的话可能会导致下载出现问题，因为程序在睡眠中,可用以下办法解决
 * 
 * 下载方法：
 *      1.将开发版正常连接好
 *      2.按住复位按键，点击下载瞬间松开复位按键
 *     
 *      1.通过跳线帽将 BOOT 0 接高电平(3.3V)
 *      2.重新上电，下载
 *    
 * 			1.使用FlyMcu擦除一下芯片，然后进行下载
 *			STMISP -> 清除芯片(z)
 */
#define configUSE_TICKLESS_IDLE                 0   

/*
 * 写入实际的CPU内核时钟频率，也就是CPU指令执行频率，通常称为Fclk
 * Fclk为供给CPU内核的时钟信号，我们所说的cpu主频为 XX MHz，
 * 就是指的这个时钟信号，相应的，1/Fclk即为cpu时钟周期；
 */
#define configCPU_CLOCK_HZ                      (SystemCoreClock)

//RTOS系统节拍中断的频率。即一秒中断的次数，每次中断RTOS都会进行任务调度
#define configTICK_RATE_HZ                      (( TickType_t )1000)

//可使用的最大优先级
#define configMAX_PRIORITIES                    (32)

//空闲任务使用的堆栈大小
#define configMINIMAL_STACK_SIZE                ((unsigned short)128)
  
//任务名字字符串长度
#define configMAX_TASK_NAME_LEN					(16)

 //系统节拍计数器变量数据类型，1表示为16位无符号整形，0表示为32位无符号整形
#define configUSE_16_BIT_TICKS                  0                      

//空闲任务放弃CPU使用权给其他同优先级的用户任务
#define configIDLE_SHOULD_YIELD					1           

//启用队列
#define configUSE_QUEUE_SETS                    1    

//开启任务通知功能，默认开启
#define configUSE_TASK_NOTIFICATIONS            1   

//使用互斥信号量
#define configUSE_MUTEXES                       1    

//使用递归互斥信号量                                            
#define configUSE_RECURSIVE_MUTEXES             1   

//为1时使用计数信号量
#define configUSE_COUNTING_SEMAPHORES           1

/* 设置可以注册的信号量和消息队列个数 */
#define configQUEUE_REGISTRY_SIZE				10                                 
                                                                       
#define configUSE_APPLICATION_TASK_TAG          0                       
                      

/*****************************************************************
              FreeRTOS与内存申请有关配置选项                                               
*****************************************************************/
//支持动态内存申请
#define configSUPPORT_DYNAMIC_ALLOCATION        1    
//支持静态内存
#define configSUPPORT_STATIC_ALLOCATION         0					
//系统所有总的堆大小
#define configTOTAL_HEAP_SIZE					((size_t)(36*1024))   


/***************************************************************
             FreeRTOS与钩子函数有关的配置选项                                            
**************************************************************/
/* 置1：使用空闲钩子（Idle Hook类似于回调函数）；置0：忽略空闲钩子
 * 
 * 空闲任务钩子是一个函数，这个函数由用户来实现，
 * FreeRTOS规定了函数的名字和参数：void vApplicationIdleHook(void )，
 * 这个函数在每个空闲任务周期都会被调用
 * 对于已经删除的RTOS任务，空闲任务可以释放分配给它们的堆栈内存。
 * 因此必须保证空闲任务可以被CPU执行
 * 使用空闲钩子函数设置CPU进入省电模式是很常见的
 * 不可以调用会引起空闲任务阻塞的API函数
 */
#define configUSE_IDLE_HOOK						0      

/* 置1：使用时间片钩子（Tick Hook）；置0：忽略时间片钩子
 * 
 * 
 * 时间片钩子是一个函数，这个函数由用户来实现，
 * FreeRTOS规定了函数的名字和参数：void vApplicationTickHook(void )
 * 时间片中断可以周期性的调用
 * 函数必须非常短小，不能大量使用堆栈，
 * 不能调用以”FromISR" 或 "FROM_ISR”结尾的API函数
 */
 /*xTaskIncrementTick函数是在xPortSysTickHandler中断函数中被调用的。因此，vApplicationTickHook()函数执行的时间必须很短才行*/
#define configUSE_TICK_HOOK						0           

//使用内存申请失败钩子函数
#define configUSE_MALLOC_FAILED_HOOK			0 

/*
 * 大于0时启用堆栈溢出检测功能，如果使用此功能 
 * 用户必须提供一个栈溢出钩子函数，如果使用的话
 * 此值可以为1或者2，因为有两种栈溢出检测方法 */
#define configCHECK_FOR_STACK_OVERFLOW			0   


/********************************************************************
          FreeRTOS与运行时间和任务状态收集有关的配置选项   
**********************************************************************/
//启用运行时间统计功能
#define configGENERATE_RUN_TIME_STATS	        0             
 //启用可视化跟踪调试
#define configUSE_TRACE_FACILITY                0    
/* 与宏configUSE_TRACE_FACILITY同时为1时会编译下面3个函数
 * prvWriteNameToBuffer()
 * vTaskList(),
 * vTaskGetRunTimeStats()
*/
#define configUSE_STATS_FORMATTING_FUNCTIONS	1                       
                                                                        
                                                                        
/********************************************************************
                FreeRTOS与协程有关的配置选项                                                
*********************************************************************/
//启用协程，启用协程以后必须添加文件croutine.c
#define configUSE_CO_ROUTINES                   0                 
//协程的有效优先级数目
#define configMAX_CO_ROUTINE_PRIORITIES         ( 2 )                   


/***********************************************************************
                FreeRTOS与软件定时器有关的配置选项      
**********************************************************************/
 //启用软件定时器
#define configUSE_TIMERS                        1                              
//软件定时器优先级
#define configTIMER_TASK_PRIORITY		        (configMAX_PRIORITIES-1)        
//软件定时器队列长度
#define configTIMER_QUEUE_LENGTH		        10                               
//软件定时器任务堆栈大小
#define configTIMER_TASK_STACK_DEPTH            (configMINIMAL_STACK_SIZE*2)    


/************************************************************
            FreeRTOS可选函数配置选项                                                     
************************************************************/
#define INCLUDE_xTaskGetSchedulerState          1                       
#define INCLUDE_vTaskPrioritySet                1
#define INCLUDE_uxTaskPriorityGet               1
#define INCLUDE_vTaskDelete                     1
#define INCLUDE_vTaskCleanUpResources           1
#define INCLUDE_vTaskSuspend                    1
#define INCLUDE_vTaskDelayUntil                 1
#define INCLUDE_vTaskDelay                      1
#define INCLUDE_eTaskGetState                   0
#define INCLUDE_xTimerPendFunctionCall          0


/******************************************************************
            FreeRTOS与中断有关的配置选项                                                 
******************************************************************/
#ifdef __NVIC_PRIO_BITS
	#define configPRIO_BITS       		__NVIC_PRIO_BITS
#else
	#define configPRIO_BITS                     4                  
#endif
//中断最低优先级
#define configLIBRARY_LOWEST_INTERRUPT_PRIORITY			15     

//系统可管理的最高中断优先级
#define configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY	5 

#define configKERNEL_INTERRUPT_PRIORITY 		( configLIBRARY_LOWEST_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )	/* 240 */

#define configMAX_SYSCALL_INTERRUPT_PRIORITY 	( configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )


/****************************************************************
            FreeRTOS与中断服务函数有关的配置选项                         
****************************************************************/
#define xPortPendSVHandler 	PendSV_Handler
#define vPortSVCHandler 	SVC_Handler


/* 以下为使用Percepio Tracealyzer需要的东西，不需要时将 configUSE_TRACE_FACILITY 定义为 0 */
#if ( configUSE_TRACE_FACILITY == 1 )
#include "trcRecorder.h"
#define INCLUDE_xTaskGetCurrentTaskHandle               1   // 启用一个可选函数（该函数被 Trace源码使用，默认该值为0 表示不用）
#endif


#endif /* FREERTOS_CONFIG_H */

3.6 Modify stm32f10x_it.c

The SysTick interrupt service function is a very important function. FreeRTOS handles all time-related things in it. SysTick is a heartbeat clock of FreeRTOS, which drives the operation of FreeRTOS, just like a human heartbeat. If there is no heartbeat, we will It is equivalent to "dead". Similarly, if FreeRTOS has no heartbeat, it will be stuck somewhere, unable to schedule tasks or run anything, so we need to implement a FreeRTOS heartbeat clock. FreeRTOS will help us Realized the configuration of SysTick startup: vPortSetupTimerInterrupt() function has been implemented in port.c file, and FreeRTOS general SysTick interrupt service function has also been implemented: xPortSysTickHandler() function has been implemented in port.c file, so when porting we just need to stm32f10x_it.crealize that we correspond (STM32) SysTick_Handler () function can be on the platform document.

FreeRTOS considers a lot for developers. PendSV_Handler() and SVC_Handler() are two very important functions for us. The xPortPendSVHandler() and vPortSVCHandler() functions have been implemented in the port.c file to prevent us from implementing it ourselves No, then stm32f10x_it.cthe we need to comment out PendSV_Handler()the SVC_Handler()two functions of.

//void SVC_Handler(void)
//{
    
    
//}

//void PendSV_Handler(void)
//{
    
    
//}

extern void xPortSysTickHandler(void);

//systick中断服务函数
void SysTick_Handler(void)
{
    
    	
    #if (INCLUDE_xTaskGetSchedulerState  == 1 )
      if (xTaskGetSchedulerState() != taskSCHEDULER_NOT_STARTED)
      {
    
    
    #endif  /* INCLUDE_xTaskGetSchedulerState */  
        xPortSysTickHandler();
    #if (INCLUDE_xTaskGetSchedulerState  == 1 )
      }
    #endif  /* INCLUDE_xTaskGetSchedulerState */
}

• Written by Leung on October 29, 2020

• Reference: Wildfire FreeRTOS video and PDF tutorial

FreeRTOS study notes (1)-transplant source code to STM32F103