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GPIO access doubt in I.MX53 SABRE Tablet

Question asked by Winston Rodrigues on Mar 11, 2013
Latest reply on Jul 22, 2016 by Biyong Sun

Dear Pals,


          I am working on IMX53_smd (sabre tablet). since I was trying to toggle the LEDs in Linux ( charge and user debug D27, D32 from schematic ) which are connected to these pins :




   But these definitions are already registered in "iomux-mx53.h" and "mx53_smd.c"

  so I tried to access the pins directly from sysfs like this....


       for MX53_PAD_EIM_D30__GPIO_30 : "echo 94 > /sys/class/gpio/export

       But when I do ls i count see any new directory..

    for MX53_PAD_PATA_DA_1__GPIO7_7 I did "echo 199 > sys/class/gpio/export

    Here also No directories created... I dont understand why .. Is it because these pins are already being used for Charge_done and USER_DEBUG ??


Another case :

       I thought I will access the free GPIO pin on the expansion connector,

   that is 40th pin on J78 i.e. MX53_PAD_GPIO_17__GPIO7_12

  So i Added this pin in "../mach-mx5/mx53_smd.c" in static iomux_v3_cfg_t mx53_smd_pads[] array..

    then i recompiled the kernel and deployed it, booted from SD card.

   But when I try to access it : echo 204 > export

                                             echo out > gpio204/direction

                                             echo 1 > gpio204/value


    But when i see the value it is still '0' and the Pin doesnt change. but direction has changed to "out"


   What am I doing wrong here ... ??