6 years ago.

Hello Paul,

As far as I know the only USB mass storage device that can be shared with the PC is the LocalFileSystem. It's a file system that connects to the Mbed board's interface chip if the interface chip has built-in storage. The LocalFileSystem meets all your requirements but it is only available on the LPC1768 and LPC11U24 boards:

• The text file located on the LocalFileSystem can be edited from the PC
• Data from the text file can be read during Mbed's program startup
• The file is non-volatile (persists on the Mbed even when the Mbed has been powered off).

A quick test:

• Connect your LPC1768 over USB to the PC.
• Create a new "config.txt" file on the MBED disk with your favourite text editor and save it.
• The following Mbed program will print the content of the "config.txt" file to the serial monitor.

#include "mbed.h"

LocalFileSystem fs("local");

int main()
{
    printf("Opening file 'config.txt'... ");    
    FILE*   fp = fopen("/local/config.txt", "r");  
    printf("%s\n", (!fp ? "Fail :(" : "OK"));
    if (!fp)
        error("error: %s (%d)\n", strerror(errno), -errno);
    while (!feof(fp)) {
        int c = fgetc(fp);
        printf("%c", c);
    }    
    printf("\r\n");    
    fclose(fp);
}