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BAW
Associate III
November 7, 2023
Solved

STM32F407 Discovery Board - FatFs_USBDisk appliaction not working when unplug and plug in again

Hello,

I have a STM32F407 Discovery Board. I am trying out the FatFs_USBDisk demo application. I am running the application from STM32CubeIDE.

When I run the application and plug in a USB flash drive, the demo application works as expected. I see the STM32.txt file on the USB drive and the Green LED4 is on. 

If I then unplug the USB flash drive and plug it back in, I get the RED error LED5.

Debugging it, I see the following is called when I unplug the USB flash drive.

f_mount(NULL, (TCHAR const*)"", 0);

When I plug the USB flash drive back in I see that

if(f_mount(&USBDISKFatFs, (TCHAR const*)USBDISKPath, 0) != FR_OK)

returns FR_OK

The demo application is failing in 

if(f_open(&MyFile, "STM32.TXT", FA_CREATE_ALWAYS | FA_WRITE) != FR_OK)

returning FR_NO_FILESYSTEM.

Specifically in the find_volume() in f_open()

If I stop the debug session and restart it the USB flash drive is mounted correctly and able to open then write the file.

Any thoughts on what is going on?

I have not modified the demo application (using as is out the box).

Thanks,

Brent

 

 

This topic has been closed for replies.
BAWBest answer
Associate III
November 9, 2023

I found the issue. In the MSC_Application() at the end the following call is made:

/* Unlink the USB disk I/O driver */
FATFS_UnLinkDriver(USBDISKPath);

 

Commenting this out as shown below allows me to plugin/unplug the USB flash drive over and over. The device is mounted correctly and can write/read files to it.

Why is this function call in the demo application?

Not sure when this should be used in an application?

 

static void MSC_Application(void)
{
 FRESULT res; /* FatFs function common result code */
 uint32_t byteswritten, bytesread; /* File write/read counts */
 uint8_t wtext[] = "This is STM32 working with FatFs"; /* File write buffer */
 uint8_t rtext[100]; /* File read buffer */
 
 /* Register the file system object to the FatFs module */
 if(f_mount(&USBDISKFatFs, (TCHAR const*)USBDISKPath, 0) != FR_OK)
 {
 /* FatFs Initialization Error */
 Error_Handler();
 }
 else
 {
 /* Create and Open a new text file object with write access */
 if(f_open(&MyFile, "STM32.TXT", FA_CREATE_ALWAYS | FA_WRITE) != FR_OK)
 {
 /* 'STM32.TXT' file Open for write Error */
 Error_Handler();
 }
 else
 {
 /* Write data to the text file */
 res = f_write(&MyFile, wtext, sizeof(wtext), (void *)&byteswritten);
 
 if((byteswritten == 0) || (res != FR_OK))
 {
 /* 'STM32.TXT' file Write or EOF Error */
 Error_Handler();
 }
 else
 {
			/* Close the open text file */
			f_close(&MyFile);

			/* Open the text file object with read access */
			if(f_open(&MyFile, "STM32.TXT", FA_READ) != FR_OK)
			{
				/* 'STM32.TXT' file Open for read Error */
				Error_Handler();
			}
			else
			{
				/* Read data from the text file */
				res = f_read(&MyFile, rtext, sizeof(rtext), (void *)&bytesread);

				if((bytesread == 0) || (res != FR_OK))
				{
					/* 'STM32.TXT' file Read or EOF Error */
					Error_Handler();
				}
				else
				{
					/* Close the open text file */
					f_close(&MyFile);

					/* Compare read data with the expected data */
					if((bytesread != byteswritten))
					{
						/* Read data is different from the expected data */
						Error_Handler();
					}
					else
					{
						/* Success of the demo: no error occurrence */
						BSP_LED_On(LED4);
					}
				}
			}
 }
 }
 }
 
 /* Unlink the USB disk I/O driver */
 // FATFS_UnLinkDriver(USBDISKPath);
}
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4 replies

BAWAuthor
Associate III
November 8, 2023

Hello,

I am trying to dig into this a little more. When starting up the FatFs_USBDisk demo application and running it the first time I plug in the USB flash drive it works. Specifically in check_fs() where it loads a sector and checks to see if it is a FAT boot sector - the boot record signature returned from the check is 0xAA55 (see figure below):

1.png

 

In the case where I unplug the USB flash drive, I see unmount is called, both LEDs turn off as expected. When I plug the USB flash drive back in check_fs() is called but the boot record signature returned from the check is not 0xAA55. It is 0 (see figure below):

2.png

Could there be a bug in the FatFs code?

Or maybe I am not running the demo application as expected?

Any thoughts on what I might be able to try?

Thanks,

Brent

 

 

 

 

AScha.3
AScha.3
Super User
November 8, 2023

just - what i do:

on usb mount / app_ready i use : 

retUSBH = f_mount(&USBfs, (TCHAR const*)USBHPath, 1);    // mount

"1" -> mount now.  (you have "0" delayed mount )  --- just try it.

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BAWAuthor
Associate III
November 9, 2023

Thank you for the reply!

I changed the the last parameter of the f_mount to 1 to mount immediately.

mount_result = f_mount(&USBDISKFatFs, (TCHAR const*)USBDISKPath, 1);

/* Register the file system object to the FatFs module */
if(mount_result != FR_OK)
{
	/* FatFs Initialization Error */
	Error_Handler();
}

When I first run the demo application and plug in a USB flash drive the f_mount() returns FR_OK. The application continues to run properly and writes/read a file to the USB flash drive. The green LED turns on. 

 

11.png

 

I then unplug the USB flash drive, the drive unmounts, and green LED turns off.

 

44.png

 

I then plug in the USB flash drive the second time. The f_mount() fails with FR_NO_FILESYSTEM.

 

22.png

 

I have tried different USB flash drives to see if that was the issue. I have the same issue with all of them.

 

Do you have this working where you are able to plug in and unplug a USB flash drive multiple times?

 

I am trying the FatFs_USBDisk from the Example Selector for STM32F407G-DISC1 within STM32CubeIDE (see below). 

 

Are you able to get this to work or have it working in another application?

 

Maybe I am not understanding how this application is suppose to work? I guess I am surprised that this example out of STMicros' SDK is not working out of the box.

Any other thoughts on what to look at or try?

 

33.png

Thanks again,

Brent

 

 

 

 

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