GPIO default state - still unclear

Discussion in 'General Discussion' started by mirots, May 20, 2014.

  1. mirots

    mirots New Member

    Dec 26, 2013
    Likes Received:
    Sorry for bringing up this question again - but what I am experiencing is different from what I was reading in manual and on forum (mainly this discussion - state-gpio-after-reboot-t297.html).

    * I am powering up Udoo with nothing attached to expansion pins except Oscilloscope on Pin 13/GND.
    * Scope shows 3.3v (HIGH), just after pressing reset button (long before Kernel is loaded)
    * When Linux boots up, I can verify that GPIO40 direction is IN on iMX6 and VALUE is 1
    * Arduino is explicitly loaded with sketch that sets GPIO13 to INPUT (I tried it without any sketch as well)

    What makes this GPIO go HIGH by default and how to change this behavior?
    (According to what is said - shared pins are configured as INPUT, so I assume nothing should pull them them up to VCC)

    I am building custom hardware which should receive instructions from iMX6 through GPIO. This is why I need it to stay LOW during power up.

    I asked this question before here, but received no answer - gpio-default-state-t811.html

    BTW - most (but not all) of other GPIOs act the same way

    Many thanks!
    Meir Tseitlin

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