GPIO SD no change

      GPIO SD no change

      Hello,

      GPIO ports of SD_A and SD_B don't change

      For example.
      echo 21 > /sys/class/gpio/export
      echo out > /sys/class/gpio/gpio21/direction
      echo 0 > /sys/class/gpio/gpio21/value

      I also tried to disable the SD in the kernel but I feel the same don't change are always 3,3V

      Thank you
      First of all you have to disable SD ports A and B in the kernel, i.e. call make menuconfig and then go to "System Time" -> "Freescale MXC Implementations" -> "Support F&S efusA9". There remove the checkmarks for "Use SD card port A" and "Use SD card port B". Now recompile the kernel. The kernel does not touch the SD card signals anymore and theoretically they can be used as GPIOs.

      BUT... the SD signals are already pin-mux-switched to SD function in U-Boot. So there are actually two ways to handle this

      1. Switch the pin-mux back to GPIO in Linux when the SD card ports are not used. However this means that for a short period of time during boot phase the pins will carry SD signals. So this is only possible if this does not matter to you.

      2. Prevent U-Boot to activate the SD signals in the first place. This will result in your own U-Boot and you have to remember to update U-Boot on all boards shipped to you.


      Please tell me which way to go and I will give instructions on how to do this.

      Your F&S Support Team
      F&S Elektronik Systeme GmbH
      As this is an international forum, please try to post in English.
      Da dies ein internationales Forum ist, bitten wir darum, Beiträge möglichst in Englisch zu verfassen.