SEGGER Embedded Studio IDE移植FreeRTOS

一、简介

SEGGER Embedded Studio虽然可以支持embOS，但是我们也可能更多的时候想移植FreeRTOS。这里我把做这个移植的操作放在这里。以便未来查阅。

在本案例中，笔者不打算使用动态内存。

二、技术路线

移植的技术路线是

1. 获取FreeRTOS源码
2. 将必要的文件复制到工程中
3. 创建FreeRTOSConfig.h并进行配置
4. 测试

2.1 获取FreeRTOS源码

这一步非常简单，就是从FreeRTOS官网下载源码包。得到的源码文件里面是这个样子。

2.2 将必要的文件复制到工程中

2.2.1 移植C文件

参考《Mastering the FreeRTOS™ Real Time Kernel》第13页的文件结构。

我们把除了croutine.c的其他的文件放到项目文件夹下新建的FreeRTOS/目录下。

2.2.2 移植portable文件

一共有2个文件要用。在FreeRTOS/Source/portable/GCC/ARM-CM4F下面把cortex-m4的编译器支持包port.c和portmacro.h考过去。

记得在Project->Option->Preprocessor的User Include Directory中加入我们新建的FreeRTOS/文件夹。

因为我没有使用动态内存，所以不需要添加heap_x.c的那些文件。那些文件在FreeRTOS/Source/portable/MemMang/下面

2.2.3 移植头文件

除了那个要自己创建的FreeRTOSConfig.h，其他的在FreeRTOSv202212.01\FreeRTOS\Source\include\下面的头文件可以都考过来。虽然有那么零星的几个其实是用不上的。

2.3 创建FreeRTOSConfig.h并进行配置

这个文件必须要自己创建的。虽然官方给了很多的模板。笔者比较推荐[官方网页的模板]。(https://www.freertos.org/a00110.html)

#ifndef FREERTOS_CONFIG_H
#define FREERTOS_CONFIG_H

/* Here is a good place to include header files that are required across
your application. */
#include "something.h"

#define configUSE_PREEMPTION                    1
#define configUSE_PORT_OPTIMISED_TASK_SELECTION 0
#define configUSE_TICKLESS_IDLE                 0
#define configCPU_CLOCK_HZ                      60000000
#define configSYSTICK_CLOCK_HZ                  1000000
#define configTICK_RATE_HZ                      250
#define configMAX_PRIORITIES                    5
#define configMINIMAL_STACK_SIZE                128
#define configMAX_TASK_NAME_LEN                 16
#define configUSE_16_BIT_TICKS                  0
#define configTICK_TYPE_WIDTH_IN_BITS           TICK_TYPE_WIDTH_16_BITS
#define configIDLE_SHOULD_YIELD                 1
#define configUSE_TASK_NOTIFICATIONS            1
#define configTASK_NOTIFICATION_ARRAY_ENTRIES   3
#define configUSE_MUTEXES                       0
#define configUSE_RECURSIVE_MUTEXES             0
#define configUSE_COUNTING_SEMAPHORES           0
#define configUSE_ALTERNATIVE_API               0 /* Deprecated! */
#define configQUEUE_REGISTRY_SIZE               10
#define configUSE_QUEUE_SETS                    0
#define configUSE_TIME_SLICING                  0
#define configUSE_NEWLIB_REENTRANT              0
#define configENABLE_BACKWARD_COMPATIBILITY     0
#define configNUM_THREAD_LOCAL_STORAGE_POINTERS 5
#define configUSE_MINI_LIST_ITEM                1
#define configSTACK_DEPTH_TYPE                  uint32_t
#define configMESSAGE_BUFFER_LENGTH_TYPE        size_t
#define configHEAP_CLEAR_MEMORY_ON_FREE         1
#define configUSE_APPLICATION_TASK_TAG          0
#define configSTATS_BUFFER_MAX_LENGTH           0xFFFF

/* Memory allocation related definitions. */
#define configSUPPORT_STATIC_ALLOCATION             1
#define configSUPPORT_DYNAMIC_ALLOCATION            1
#define configKERNEL_PROVIDED_STATIC_MEMORY         1
#define configTOTAL_HEAP_SIZE                       10240
#define configAPPLICATION_ALLOCATED_HEAP            1
#define configSTACK_ALLOCATION_FROM_SEPARATE_HEAP   1
#define configENABLE_HEAP_PROTECTOR                 1

/* Hook function related definitions. */
#define configUSE_IDLE_HOOK                     0
#define configUSE_TICK_HOOK                     0
#define configCHECK_FOR_STACK_OVERFLOW          0
#define configUSE_MALLOC_FAILED_HOOK            0
#define configUSE_DAEMON_TASK_STARTUP_HOOK      0
#define configUSE_SB_COMPLETED_CALLBACK         0

/* Run time and task stats gathering related definitions. */
#define configGENERATE_RUN_TIME_STATS           0
#define configUSE_TRACE_FACILITY                0
#define configUSE_STATS_FORMATTING_FUNCTIONS    0

/* Co-routine related definitions. */
#define configUSE_CO_ROUTINES                   0
#define configMAX_CO_ROUTINE_PRIORITIES         1

/* Software timer related definitions. */
#define configUSE_TIMERS                        1
#define configTIMER_TASK_PRIORITY               3
#define configTIMER_QUEUE_LENGTH                10
#define configTIMER_TASK_STACK_DEPTH            configMINIMAL_STACK_SIZE

/* Interrupt nesting behaviour configuration. */
#define configKERNEL_INTERRUPT_PRIORITY         [dependent of processor]
#define configMAX_SYSCALL_INTERRUPT_PRIORITY    [dependent on processor and application]
#define configMAX_API_CALL_INTERRUPT_PRIORITY   [dependent on processor and application]

/* Define to trap errors during development. */
#define configASSERT( ( x ) ) if( ( x ) == 0 ) vAssertCalled( __FILE__, __LINE__ )

/* FreeRTOS MPU specific definitions. */
#define configINCLUDE_APPLICATION_DEFINED_PRIVILEGED_FUNCTIONS 0
#define configTOTAL_MPU_REGIONS                                8 /* Default value. */
#define configTEX_S_C_B_FLASH                                  0x07UL /* Default value. */
#define configTEX_S_C_B_SRAM                                   0x07UL /* Default value. */
#define configENFORCE_SYSTEM_CALLS_FROM_KERNEL_ONLY            1
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS             1
#define configENABLE_ERRATA_837070_WORKAROUND                  1
#define configUSE_MPU_WRAPPERS_V1                              0
#define configPROTECTED_KERNEL_OBJECT_POOL_SIZE                10
#define configSYSTEM_CALL_STACK_SIZE                           128
#define configENABLE_ACCESS_CONTROL_LIST                       1

/* ARMv8-M secure side port related definitions. */
#define secureconfigMAX_SECURE_CONTEXTS         5

/* Optional functions - most linkers will remove unused functions anyway. */
#define INCLUDE_vTaskPrioritySet                1
#define INCLUDE_uxTaskPriorityGet               1
#define INCLUDE_vTaskDelete                     1
#define INCLUDE_vTaskSuspend                    1
#define INCLUDE_xResumeFromISR                  1
#define INCLUDE_vTaskDelayUntil                 1
#define INCLUDE_vTaskDelay                      1
#define INCLUDE_xTaskGetSchedulerState          1
#define INCLUDE_xTaskGetCurrentTaskHandle       1
#define INCLUDE_uxTaskGetStackHighWaterMark     0
#define INCLUDE_uxTaskGetStackHighWaterMark2    0
#define INCLUDE_xTaskGetIdleTaskHandle          0
#define INCLUDE_eTaskGetState                   0
#define INCLUDE_xEventGroupSetBitFromISR        1
#define INCLUDE_xTimerPendFunctionCall          0
#define INCLUDE_xTaskAbortDelay                 0
#define INCLUDE_xTaskGetHandle                  0
#define INCLUDE_xTaskResumeFromISR              1

/* A header file that defines trace macro can be included here. */

#endif /* FREERTOS_CONFIG_H */
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当然这个只是个模板。比较好的原因是这里面的每一个定义下面都有说明。我们稍加修改就可以了。
这里，笔者删掉了#include "something.h"。

2.3.1 处理中断优先级

下面这三句

/* Interrupt nesting behaviour configuration. */
#define configKERNEL_INTERRUPT_PRIORITY         [dependent of processor]
#define configMAX_SYSCALL_INTERRUPT_PRIORITY    [dependent on processor and application]
#define configMAX_API_CALL_INTERRUPT_PRIORITY   [dependent on processor and application]
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根据stm32f407改成了

/* Interrupt nesting behaviour configuration. */
#define configKERNEL_INTERRUPT_PRIORITY         ( 15 << 4 )
#define configMAX_SYSCALL_INTERRUPT_PRIORITY    ( 5 << 4 )
#define configMAX_API_CALL_INTERRUPT_PRIORITY  
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因为STM32F4的中断优先级是0 - 15，所以我设置成上面的参数。当然如果觉得不保险的话还可以参考例程。

2.3.2 configASSERT( x )的处理

这个宏的处理方法非常多。但是如果并不真的用它，可以像我这样处理。

/* Define to trap errors during development. */
#define configASSERT( x ) if( ( x ) == 0 ) { taskDISABLE_INTERRUPTS(); for( ;; ); }
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2.3.3 关于系统时钟、configCPU_CLOCK_HZ和configSYSTICK_CLOCK_HZ的一点说明

为了测试方便，笔者这里只是使用了芯片内部的RC震荡时钟。所以要把configCPU_CLOCK_HZ设置成16MHz。

关于configCPU_CLOCK_HZ和configSYSTICK_CLOCK_HZ这个的设计的初衷我不清楚。但是根据调试的效果来看，如果定义了configSYSTICK_CLOCK_HZ，系统的sysTick会使能8分频。

2.3.4 动态内存和vApplicationGetIdleTaskMemory符号

把configSUPPORT_DYNAMIC_ALLOCATION关掉。但是编译后会出现要vApplicationGetIdleTaskMemory这个符号的问题。

参考官网上FreeRTOSConfig.h的模板的阐述，点一下configSUPPORT_STATIC_ALLOCATION的蓝字，就可以找到解决方案。就是把后面的代码加上去。

笔者的做法是在工程中建立一个新的文件，起名叫user_port.c，把这些代码加进去就好了。

/* configSUPPORT_STATIC_ALLOCATION is set to 1, so the application must provide an
implementation of vApplicationGetIdleTaskMemory() to provide the memory that is
used by the Idle task. */
void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuffer,
                                    StackType_t **ppxIdleTaskStackBuffer,
                                    configSTACK_DEPTH_TYPE *puxIdleTaskStackSize )
{
/* If the buffers to be provided to the Idle task are declared inside this
function then they must be declared static - otherwise they will be allocated on
the stack and so not exists after this function exits. */
static StaticTask_t xIdleTaskTCB;
static StackType_t uxIdleTaskStack[ configMINIMAL_STACK_SIZE ];

    /* Pass out a pointer to the StaticTask_t structure in which the Idle task's
    state will be stored. */
    *ppxIdleTaskTCBBuffer = &xIdleTaskTCB;

    /* Pass out the array that will be used as the Idle task's stack. */
    *ppxIdleTaskStackBuffer = uxIdleTaskStack;

    /* Pass out the size of the array pointed to by *ppxIdleTaskStackBuffer.
    Note that, as the array is necessarily of type StackType_t,
    configMINIMAL_STACK_SIZE is specified in words, not bytes. */
    *puxIdleTaskStackSize = configMINIMAL_STACK_SIZE;
}
/*-----------------------------------------------------------*/

/* configSUPPORT_STATIC_ALLOCATION and configUSE_TIMERS are both set to 1, so the
application must provide an implementation of vApplicationGetTimerTaskMemory()
to provide the memory that is used by the Timer service task. */
void vApplicationGetTimerTaskMemory( StaticTask_t **ppxTimerTaskTCBBuffer,
                                     StackType_t **ppxTimerTaskStackBuffer,
                                     configSTACK_DEPTH_TYPE *puxTimerTaskStackSize )
{
/* If the buffers to be provided to the Timer task are declared inside this
function then they must be declared static - otherwise they will be allocated on
the stack and so not exists after this function exits. */
static StaticTask_t xTimerTaskTCB;
static StackType_t uxTimerTaskStack[ configTIMER_TASK_STACK_DEPTH ];

    /* Pass out a pointer to the StaticTask_t structure in which the Timer
    task's state will be stored. */
    *ppxTimerTaskTCBBuffer = &xTimerTaskTCB;

    /* Pass out the array that will be used as the Timer task's stack. */
    *ppxTimerTaskStackBuffer = uxTimerTaskStack;

    /* Pass out the size of the array pointed to by *ppxTimerTaskStackBuffer.
    Note that, as the array is necessarily of type StackType_t,
    configTIMER_TASK_STACK_DEPTH is specified in words, not bytes. */
    *puxTimerTaskStackSize = configTIMER_TASK_STACK_DEPTH;
}
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2.3.4 操作系统那三个系统调用

我们都知道，RTOS的运行离不开SVC_Handler、PendSV_Handler和SysTick_Handler。但是系统已经给实现了vPortSVCHandler、xPortPendSVHandler和xPortSysTickHandler。这里只要用#define把名称对应一下就可以了。

/* A header file that defines trace macro can be included here. */
#define vPortSVCHandler SVC_Handler
#define xPortPendSVHandler PendSV_Handler
#define xPortSysTickHandler SysTick_Handler
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2.3.5 FreeRTOSConfig.h的代码

根据上面的操作，笔者最后的FreeRTOSConfig.h的代码如下所示

#ifndef FREERTOS_CONFIG_H
#define FREERTOS_CONFIG_H

/* Here is a good place to include header files that are required across
your application. */

#define configUSE_PREEMPTION                    1
#define configUSE_PORT_OPTIMISED_TASK_SELECTION 0
#define configUSE_TICKLESS_IDLE                 0
#define configCPU_CLOCK_HZ                      16000000
//#define configSYSTICK_CLOCK_HZ                  16000000
#define configTICK_RATE_HZ                      1000
#define configMAX_PRIORITIES                    255
#define configMINIMAL_STACK_SIZE                128
#define configMAX_TASK_NAME_LEN                 16
#define configUSE_16_BIT_TICKS                  0
#define configTICK_TYPE_WIDTH_IN_BITS           TICK_TYPE_WIDTH_16_BITS
#define configIDLE_SHOULD_YIELD                 1
#define configUSE_TASK_NOTIFICATIONS            1
#define configTASK_NOTIFICATION_ARRAY_ENTRIES   3
#define configUSE_MUTEXES                       0
#define configUSE_RECURSIVE_MUTEXES             0
#define configUSE_COUNTING_SEMAPHORES           0
#define configUSE_ALTERNATIVE_API               0 /* Deprecated! */
#define configQUEUE_REGISTRY_SIZE               10
#define configUSE_QUEUE_SETS                    0
#define configUSE_TIME_SLICING                  0
#define configUSE_NEWLIB_REENTRANT              0
#define configENABLE_BACKWARD_COMPATIBILITY     0
#define configNUM_THREAD_LOCAL_STORAGE_POINTERS 5
#define configUSE_MINI_LIST_ITEM                1
#define configSTACK_DEPTH_TYPE                  uint32_t
#define configMESSAGE_BUFFER_LENGTH_TYPE        size_t
#define configHEAP_CLEAR_MEMORY_ON_FREE         1
#define configUSE_APPLICATION_TASK_TAG          0
#define configSTATS_BUFFER_MAX_LENGTH           0xFFFF

/* Memory allocation related definitions. */
#define configSUPPORT_STATIC_ALLOCATION             1
#define configSUPPORT_DYNAMIC_ALLOCATION            0
#define configKERNEL_PROVIDED_STATIC_MEMORY         1
#define configTOTAL_HEAP_SIZE                       1024
#define configAPPLICATION_ALLOCATED_HEAP            1
#define configSTACK_ALLOCATION_FROM_SEPARATE_HEAP   1
#define configENABLE_HEAP_PROTECTOR                 1

/* Hook function related definitions. */
#define configUSE_IDLE_HOOK                     0
#define configUSE_TICK_HOOK                     0
#define configCHECK_FOR_STACK_OVERFLOW          0
#define configUSE_MALLOC_FAILED_HOOK            0
#define configUSE_DAEMON_TASK_STARTUP_HOOK      0
#define configUSE_SB_COMPLETED_CALLBACK         0

/* Run time and task stats gathering related definitions. */
#define configGENERATE_RUN_TIME_STATS           0
#define configUSE_TRACE_FACILITY                0
#define configUSE_STATS_FORMATTING_FUNCTIONS    0

/* Co-routine related definitions. */
#define configUSE_CO_ROUTINES                   0
#define configMAX_CO_ROUTINE_PRIORITIES         1

/* Software timer related definitions. */
#define configUSE_TIMERS                        1
#define configTIMER_TASK_PRIORITY               3
#define configTIMER_QUEUE_LENGTH                10
#define configTIMER_TASK_STACK_DEPTH            configMINIMAL_STACK_SIZE

/* Interrupt nesting behaviour configuration. */
#define configKERNEL_INTERRUPT_PRIORITY         ( 15 )
#define configMAX_SYSCALL_INTERRUPT_PRIORITY    ( 5 )
#define configMAX_API_CALL_INTERRUPT_PRIORITY   

/* Define to trap errors during development. */
#define configASSERT( x ) if( ( x ) == 0 ) { taskDISABLE_INTERRUPTS(); for( ;; ); }

/* FreeRTOS MPU specific definitions. */
#define configINCLUDE_APPLICATION_DEFINED_PRIVILEGED_FUNCTIONS 0
#define configTOTAL_MPU_REGIONS                                8 /* Default value. */
#define configTEX_S_C_B_FLASH                                  0x07UL /* Default value. */
#define configTEX_S_C_B_SRAM                                   0x07UL /* Default value. */
#define configENFORCE_SYSTEM_CALLS_FROM_KERNEL_ONLY            1
#define configALLOW_UNPRIVILEGED_CRITICAL_SECTIONS             1
#define configENABLE_ERRATA_837070_WORKAROUND                  1
#define configUSE_MPU_WRAPPERS_V1                              0
#define configPROTECTED_KERNEL_OBJECT_POOL_SIZE                10
#define configSYSTEM_CALL_STACK_SIZE                           128
#define configENABLE_ACCESS_CONTROL_LIST                       1

/* ARMv8-M secure side port related definitions. */
#define secureconfigMAX_SECURE_CONTEXTS         5

/* Optional functions - most linkers will remove unused functions anyway. */
#define INCLUDE_vTaskPrioritySet                1
#define INCLUDE_uxTaskPriorityGet               1
#define INCLUDE_vTaskDelete                     1
#define INCLUDE_vTaskSuspend                    1
#define INCLUDE_xResumeFromISR                  1
#define INCLUDE_vTaskDelayUntil                 1
#define INCLUDE_vTaskDelay                      1
#define INCLUDE_xTaskGetSchedulerState          1
#define INCLUDE_xTaskGetCurrentTaskHandle       1
#define INCLUDE_uxTaskGetStackHighWaterMark     0
#define INCLUDE_uxTaskGetStackHighWaterMark2    0
#define INCLUDE_xTaskGetIdleTaskHandle          0
#define INCLUDE_eTaskGetState                   0
#define INCLUDE_xEventGroupSetBitFromISR        1
#define INCLUDE_xTimerPendFunctionCall          0
#define INCLUDE_xTaskAbortDelay                 0
#define INCLUDE_xTaskGetHandle                  0
#define INCLUDE_xTaskResumeFromISR              1

/* A header file that defines trace macro can be included here. */
#define vPortSVCHandler SVC_Handler
#define xPortPendSVHandler PendSV_Handler
#define xPortSysTickHandler SysTick_Handler
#endif /* FREERTOS_CONFIG_H */
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2.4 测试

参考手册，做了下面的这样一个测试用例。

/*********************************************************************
*                    SEGGER Microcontroller GmbH                     *
*                        The Embedded Experts                        *
**********************************************************************

-------------------------- END-OF-HEADER -----------------------------

File    : main.c
Purpose : Generic application start

*/

#include "stm32f407xx.h" 
#include <stdio.h>
#include <stdlib.h>
#include "FreeRTOS.h"
#include "task.h"
#include "hardware.h"

/*********************************************************************
*
*       main()
*
*  Function description
*   Application entry point.
*
**********************************************************************/

#define STACK_SIZE 200
static void vTaskMain(void *p);
static StaticTask_t xTaskBuffer;
static StackType_t xStack[ STACK_SIZE ];

int main(void) {
  int i;
  SystemCoreClockUpdate();
  prvSetupHardware();
  TaskHandle_t xHandle = NULL;
    /* Create the task without using any dynamic memory allocation. */
      xHandle = xTaskCreateStatic(
      vTaskMain,              /* Function that implements the task. */
      "NAME",                 /* Text name for the task. */
      STACK_SIZE,             /* The number of indexes in the xStack array. */
      ( void * ) 1,           /* Parameter passed into the task. */
      155,       /* Priority at which the task is created. */
      xStack,                 /* Array to use as the task's stack. */
      &xTaskBuffer );         /* Variable to hold the task's data structure. */
  vTaskStartScheduler();
  while(1);
}

void vTaskMain(void *p){
  while(1){
    GPIOA->BSRR = 1<<7;
    vTaskDelay(pdMS_TO_TICKS(10));
    GPIOA->BSRR = 1<<7<<16;
    vTaskDelay(pdMS_TO_TICKS(20));
  }
}

/*************************** End of file ****************************/

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运行，用示波器测PA7的输出。

三、 总结

根据上述步骤，完成FreeRTOS的移植。但是本例子中没有采用到动态内存。如果要启动动态内存，就在FreeRTOSConfig.h中把configSUPPORT_DYNAMIC_ALLOCATION这一项启用；将heap_x.c挑1个放入工程文件夹中；手动实现vPortFree函数。这次这里就不做介绍。