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USB Host MSD and working with files > 512 Bytes

Topic last updated 08 Mar 2012, by Adam Champy. 1 reply
Adam Champy
08 Mar 2012

Hi -

I've been trying to make a very basic function that takes the contents of a file from a USB flash drive and turns the file into HEX/text for sending over a serial link (eg UART)

As a test, I've tried copying the file, a JPG image file to a Text file. When I host the image file, a 125kB file, in the MBED's LocalFileSystem, the conversion works flawlessly. I effectively can use fgetc and fputc for the entire file.

But - My issue is this:

When I am using MSCUsbHost, I am only able to read 4096 bits/512 bytes - which I'm pretty sure is the first block of the flash drive - and nothing more using fread before I get to an EOF. Is it possible to read files using fread and write them using fwrite on USB mass storage devices?

Adam Champy
08 Mar 2012

Solved!

My system was grabbing a different file than expected - which was only 512 kbytes!

Sorry!