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Thread: Hard reset - does it wipe the EEProm?

  1. #1

    Hard reset - does it wipe the EEProm?

    I had to hard reset (hold button when inserting USB) my T36. (was connecting to a new PC to test a newer arduino/teensyduino build and it fell over the first time).
    All working fine now, but the whole EEProm is now all set to 1.
    Is this expected/normal behaviour? I did a search but couldn't find any reference.

    Darcy.

  2. #2
    Senior Member+ manitou's Avatar
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    Jan 2013
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    Normally, pushing the program button shouldn't erase EEPROM, BUT if you hold the program button for 15 seconds (actually, between 13 to 17 seconds) the chip is fully erased, including eeprom data.

    ref: https://forum.pjrc.com/threads/47149...l=1#post157093

  3. #3
    Senior Member
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    Jul 2014
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    Adding:
    Assuming Teensy is powered only by USB
    - disconnect and reconnecting USB-power to Teensy, resets PC USB bus and restarts existing program
    - disconnect and reconnecting USB-power to Teensy while button pressed, resets PC USB bus and forces download

    If there is a USB hub involved, it may be necessary to disconnect the USB hub from PC to reset PC USB bus (happens to me very often during program development)

  4. #4
    Thanks for the info, very interesting - I am 95% confident that I pressed the button for less than 10 seconds.
    In hindsight, I had just been blindly hacking the boards.txt and usb_desc.h (adding MTP USB to my large project), so I will re-trace my steps and see if I can repeat.
    Good to know about the use of a hub - I do often use one.

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