Slow SD access on DUE + modified RAMPS1.4

Hi all,

Does anyone know why I gt slower SD access on a DUE with a RAMPS modified for 3.3V than I get on a MEGA + RAMPS?

I have removed the level shifting between the DUE+RAMPS as the DUE is already 3.3V, but otherwise everything is wired the same. Same SD card works great on MEGA.

But if I connect the SD card to the DUE then it takes 10 or 15 seconds before the directory listing shows, and scrolling in the files are dreadfully slow.

Any ideas?

Thank you,


  • Check with host if you get log messages. Maybe sd card detect causes it to remount constatntly which makes everything slow.
  • Something strange is happening.

    If I start the DUE without an SD card, then insert it, then the DUE crashes after two or three seconds then starts up with the SD mounted and it lists the files on the serial port.

    If I then remove the card and put it back then I get this:
    09:25:26.401 : SD card inserted
    09:25:27.761 : Begin file list
    09:25:28.001 : BDAFFA05005 - Coin Reject  2795377
    09:25:28.001 : BDAFFA05007-1 Note Chute 1 2039352

    There are 1.2 seconds between Card Inserted and file list.

    The same card on a MEGA gives me this:
    09:18:07.398 : SD card inserted
    09:18:08.018 : Begin file list
    09:18:08.038 : BDAFFA05005 - Coin Reject  2795377
    09:18:08.038 : BDAFFA05007-1 Note Chute 1 2039352

    That is 0.6 seconds, half the time.

    Is the MEGA running hardware SPI and the DUE software?

    Thank you,

  • It is using hardware spi for reading. I see you have very long names. Due to memory restrictions on avr names must be < 26 chars. I'm not sure what happens if you have longer names, but maybe that is part of your problem. Please try formatting and only add short names with ascii chars only.

    Unfortunately the sd routines are not mine so I have no deep understanding of what they can and how they work. It is a freely available library modified to work int his context.
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