代码收藏家技术教程 2024-09-12

【STM32】FatFs文件系统多线程支持实现：同时读写多个文件基于FreeRTOS实战指南

问题描述

正常来说，FATFS在读写单个文件是没问题的，但是有时候需要开两个以上线程，同时打开两个以上文件，并同时进行读写操作，实测如果不开启FATFS的多线程支持，直接在每个线程打开文件并写入，会有出错或者出现只有一个线程的文件能写入的问题，这样就需要开启FATFS自带的多线程支持功能了。

解决办法

FATFS的多任务支持其实就是一个互斥锁管理（信号量会有优先级反转）
以freertos，fatfsR0.14b为例

1.

ffconf.h修改以下下配置

/* #include <somertos.h>	// O/S definitions */
#include "FreeRTOS.h"
#include "semphr.h"
#define FF_FS_REENTRANT	1
#define FF_FS_TIMEOUT	1000
#define FF_SYNC_t		SemaphoreHandle_t
/* The option FF_FS_REENTRANT switches the re-entrancy (thread safe) of the FatFs
/  module itself. Note that regardless of this option, file access to different
/  volume is always re-entrant and volume control functions, f_mount(), f_mkfs()
/  and f_fdisk() function, are always not re-entrant. Only file/directory access
/  to the same volume is under control of this function.
/
/   0: Disable re-entrancy. FF_FS_TIMEOUT and FF_SYNC_t have no effect.
/   1: Enable re-entrancy. Also user provided synchronization handlers,
/      ff_req_grant(), ff_rel_grant(), ff_del_syncobj() and ff_cre_syncobj()
/      function, must be added to the project. Samples are available in
/      option/syscall.c.
/
/  The FF_FS_TIMEOUT defines timeout period in unit of time tick.
/  The FF_SYNC_t defines O/S depe

注意#define FF_SYNC_t SemaphoreHandle_t中的SemaphoreHandle_t原本是HANDLE，要把它改成自己所用操作系统对应互斥信号量的同步处理声明。

2.

修改ffsystem.c（注意老版的改syscall.c）,添加或者在原程序修改为以下接口函数，把相应用到的操作系统相关的解开注释就行。

#if FF_FS_REENTRANT	/* Mutal exclusion */

/*------------------------------------------------------------------------*/
/* Create a Synchronization Object                                        */
/*------------------------------------------------------------------------*/
/* This function is called in f_mount() function to create a new
/  synchronization object for the volume, such as semaphore and mutex.
/  When a 0 is returned, the f_mount() function fails with FR_INT_ERR.
*/

//const osMutexDef_t Mutex[FF_VOLUMES];	/* CMSIS-RTOS */


int ff_cre_syncobj (	/* 1:Function succeeded, 0:Could not create the sync object */
	BYTE vol,			/* Corresponding volume (logical drive number) */
	FF_SYNC_t* sobj		/* Pointer to return the created sync object */
)
{
//	/* Win32 */
//	*sobj = CreateMutex(NULL, FALSE, NULL);
//	return (int)(*sobj != INVALID_HANDLE_VALUE);

	/* uITRON */
//	T_CSEM csem = {TA_TPRI,1,1};
//	*sobj = acre_sem(&csem);
//	return (int)(*sobj > 0);
    /* uC/OS-III */
//	OS_ERR err;
//	
//	OSMutexCreate ((OS_MUTEX*) sobj,
//                     (CPU_CHAR*) "FATFS Mutex",
//                     (OS_ERR*) &err);
//	//return (int)(err == OS_ERR_NONE );
//	return 1;

	/* FreeRTOS */
	*sobj = xSemaphoreCreateMutex();
	return (int)(*sobj != NULL);

	/* CMSIS-RTOS */
//	*sobj = osMutexCreate(Mutex + vol);
//	return (int)(*sobj != NULL);
}

/*------------------------------------------------------------------------*/
/* Delete a Synchronization Object                                        */
/*------------------------------------------------------------------------*/
/* This function is called in f_mount() function to delete a synchronization
/  object that created with ff_cre_syncobj() function. When a 0 is returned,
/  the f_mount() function fails with FR_INT_ERR.
*/

int ff_del_syncobj (	/* 1:Function succeeded, 0:Could not delete due to an error */
	FF_SYNC_t sobj		/* Sync object tied to the logical drive to be deleted */
)
{
//	/* Win32 */
//	return (int)CloseHandle(sobj);

	/* uITRON */
//	return (int)(del_sem(sobj) == E_OK);

	/* uC/OS-III */
//	OS_ERR err;
//	OSMutexDel(&sobj, OS_OPT_DEL_ALWAYS, &err);
//	return (int)(err == OS_ERR_NONE );

	/* FreeRTOS */
  vSemaphoreDelete(sobj);
	return 1;

	/* CMSIS-RTOS */
//	return (int)(osMutexDelete(sobj) == osOK);
}

/*------------------------------------------------------------------------*/
/* Request Grant to Access the Volume                                     */
/*------------------------------------------------------------------------*/
/* This function is called on entering file functions to lock the volume.
/  When a 0 is returned, the file function fails with FR_TIMEOUT.
*/

int ff_req_grant (	/* 1:Got a grant to access the volume, 0:Could not get a grant */
	FF_SYNC_t sobj	/* Sync object to wait */
)
{
//	/* Win32 */
//	return (int)(WaitForSingleObject(sobj, FF_FS_TIMEOUT) == WAIT_OBJECT_0);

	/* uITRON */
//	return (int)(wai_sem(sobj) == E_OK);

	/* uC/OS-III */
//	OS_ERR err;

//	OSMutexPend(&sobj,FF_FS_TIMEOUT, OS_OPT_PEND_BLOCKING,0, &err);
//	return (int)(err == OS_ERR_NONE );

	/* FreeRTOS */
	return (int)(xSemaphoreTake(sobj, FF_FS_TIMEOUT) == pdTRUE);

	/* CMSIS-RTOS */
//	return (int)(osMutexWait(sobj, FF_FS_TIMEOUT) == osOK);
}

/*------------------------------------------------------------------------*/
/* Release Grant to Access the Volume                                     */
/*------------------------------------------------------------------------*/
/* This function is called on leaving file functions to unlock the volume.
*/

void ff_rel_grant (
	FF_SYNC_t sobj	/* Sync object to be signaled */
)
{
//	/* Win32 */
//	ReleaseMutex(sobj);

	/* uITRON */
//	sig_sem(sobj);

	/* uC/OS-III */
//	OS_ERR err;
// OSMutexPost ((OS_MUTEX*) &sobj,
//                   (OS_OPT)     OS_OPT_POST_NONE,					//2??′DDì?êa2ù×÷￡??′2????1μ÷?è
//                   (OS_ERR*)    &err);
	/* FreeRTOS */
	xSemaphoreGive(sobj);

	/* CMSIS-RTOS */
//	osMutexRelease(sobj);
}

#endif