I have been trying to use the different GPIO-Pins reserved for eMMC and tried to use them as GPIO input Pins. Specifically I have been trying to enable P8_20(Pin 63) as input Pin. My current problem is that even with no input connection this pin is constantly high and after connecting it to a circuit with a test LED, the LED started to glow.
I have been following these two tutorials in order to enable the conflicting PINS:
- https://github.com/modmaker/BeBoPr/wiki/BeBoPr-goes-Black
- http://blog.machinekit.io/2013/06/black-is-white-is-grey.html
Specifically my steps were the following;
-
Create a bootable SD-card with the latest offical linux image(3.8.13-bone70)
-
Enable the eMMC hardware reset pin while logged onto the Beaglebone eMMC using the mmc-utils-program,from git clone https://kernel.googlesource.com/pub/scm/linux/kernel/git/cjb/mmc-utils. I chose /dev/mmcblk0 as device for the command, not sure if that was the right one
-
Disabled the boot on the beaglebone with the command "
sudo dd if=/dev/zero of=/dev/mmcblk1 bs=1024 count=1024", executed while logged in on the Beaglebone -
Disabled the eMMC and HDMI cape through the command in the uEntv.txt on the SD-card (found the uEntv.txt file in /boot, uboot is an empty folder on the SD-card)
-
Added "
mmc dev 1\n mmc rstn 1\n`` gpio set 52" to the beginning of the uEntv.txt file(\n just inserted here to save space the uEntv.txt file has newlines instead) -
Wrote a Device Tree overlay file that sets the status of Pin 63(33in pins file) to 37 (from the original 32)
-
Loaded my Device Tree Overlay into the Slots file in capemngr
-
Echoed 63 to the export file in gpios
After all these steps the Pin is still displaying a high value without any kind of circuitry attached.
The Beaglebone is booting correctly from SD and the Slots file shows that the eMMC cape has been disabled. The Pins file displays 37 as value for Pin 33. The exported direction is set to input. I have executed reboots between most of the above mentioned steps. I have also decompiled the am335x-boneblack.dtb file and ensured that the status of mmc2 is set to disabled.
I am unfortunatly a Computer Scientist with limited background on electronics, so I am unsure if I have to connect something to the Beaglebone or if I have to set anymore values.
I also can not use different Pins as I am working with a Cape that requires this Pin and some additional ones as input Pins.
Any feedback or tipps are appreciated.
Best regards
Sebastian