nRF52840 SDK16 - USB MSC example - How to check if FAT volume exists

[Nikosant03]

Hi everyone,

I am working on the USB MSC example. I am able to create files and perform read and write operations. 

Now what I want is to check if there is a FAT volume when the system restarts. Is there any function for checking this? Because I do not want to accidentally format the disk (call to f_mkfs())

So, how could I ensure during start up that the disk has a FAT volume?

Thanks in advance

Nick

[Jørgen Holmefjord]

Hi,

f_mount() should return FR_NO_FILESYSTEM if there is no FAT file system present on the logical drive.

Best regards,
Jørgen

[Nikosant03]

Hi Jorsen and thank you for your answer

Everytime the system reset/restart I have to call the f_mount() function? I mean, what if the disk is already be mounted and I call f_mount() again? Is it safe? Re-mount the default drive will reinitialize the filesystem.. Could this lead to data loss?

This is the first time I come across with file systems so excuse my ignorance

Nick

[Jørgen Holmefjord]

Nikosant03 said:

Everytime the system reset/restart I have to call the f_mount() function?

Yes, if you want to perform any file/directory operations. From the description of the function: "Prior to perform any file/directory operations, a filesystem object needs to be registered with f_mount function for the logical drive."

Nikosant03 said:

what if the disk is already be mounted and I call f_mount() again? Is it safe? Re-mount the default drive will reinitialize the filesystem.. Could this lead to data loss?

That should be fine, it will just re-init the filesystem object (FATFS* fs). However, note the following line from the description: "If there is any open object of file or directory on the logical drive, the object will be invalidated by this function."

[Nikosant03]

Thank you for your fast support Jorgen!!