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Thread: Teensy 4.0: Ethernet Library causing SD Errors

  1. #1
    Senior Member
    Join Date
    Jun 2017

    Teensy 4.0: Ethernet Library causing SD Errors

    This problem has been reported in:

    I have been having lots of problems with my SD card attachment which is connected to a Teensy 4.0 along with a WIZ850IO.

    I have followed all the guidelines regarding setup. I have also tried different SD cards. Using the SD library, the card would only be recognized about half the time.

    After I gave up on the Teensy's SD library, I switched to the SDFat-Beta library. In this case, the card is recognized 100% of the time. However, after writing a couple of relatively small files (20kb), the card stops writing and the filesystem is corrupted with very large files (1 MB).

    ================================================== ====================

    I have isolated the reason to the Ethernet side. When I did not use Ethernet.begin, the SD card worked 100% of the time.

    When I executed the following statements before writing to the SD card, they did not help. I still got file corruption.

    // disable Ethernet chip
    pinMode(10, OUTPUT);
    digitalWrite(10, HIGH);
    I have tried both the Ethernet and the Ethernet2 libraries.

    With my limited knowledge of the SPI bus, this leads me to believe that there is a bug in the Ethernet library when used with a Teensy 4.0.

    BTW, in the absence of SD-card operations, the Ethernet library works fine. So this problem can only be duplicated by using an SD card in addition to starting the Ethernet interface.

  2. #2
    Senior Member
    Join Date
    Jun 2017
    Sorry for the double post. A more detailed post can be found at:

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