How to Modify text file in USB host mode

[waleedaslam89]

Posted on August 09, 2012 at 11:28

does anyone have idea how to modify a text file in usb host mode using Fatfs library. 

I have a working project of usb host and successfully writing a new file using the code below. but i dont have the idea how to modify or append info in already existing file.

/* Register work area for logical drives */

    f_mount(0, &fatfs);        if(f_open(&file, ''0:STM32.TXT'',FA_CREATE_ALWAYS | FA_WRITE) == FR_OK)    {       /* Write buffer to file */      bytesToWrite = sizeof(writeTextBuff);       res= f_write (&file, writeTextBuff, bytesToWrite, (void *)&bytesWritten);               if((bytesWritten == 0) || (res != FR_OK)) /*EOF or Error*/      {        USART2_SendData_s(''> STM32.TXT CANNOT be writen.\n'');      }      else      {        USART2_SendData_s(''> 'STM32.TXT' file created\n'');      }            /*close file and filesystem*/      f_close(&file);    } 

[Tesla DeLorean]

Posted on August 09, 2012 at 14:53

Use FA_OPEN_ALWAYS, and f_lseek()

http://elm-chan.org/fsw/ff/en/open.html

Perhaps :

FIL f;

if( f_open( &f, ''log.txt'', FA_WRITE|FA_OPEN_ALWAYS ) == FR_OK ) { u32 wrt=0;

f_lseek( &f, f.fsize );

f_write( &f, buffer, strlen(buffer), &wrt ); f_close( &f); }