HDMI and GPIO2 pins on BeagleBone Black BBB

[Paulo Sherring]

Hi there!
I am developing a software that is to run on a BBB, runing Debian  wheezy with 3.14.2x-ti. The sofware is goind to control stepper motors, much like those CNC controllers that I have seen around here, such as machine kit et cetera.
So, as I dont have need for hdmi, I am using its pins for my own aplication, since there are a lot of GPIO2 pins in the headers and using a single GPIO allows the better usage of memory access, since more pins can be set in a single memory read-modify-write operation, or even a single write do SETDATAOUT and CLEARDATAOUT registers.
I have found a few outdated sources that indicates that I dont need to disable the framer, since it only acts when a display is detected. Some other more recent post point that I can disable it changing uEnv.txt, but on my image, I can't figure how to do this, since the only thing on my uEnv.txt is the kernel string.
Can anyone give me a hint on which way is the way?
Thanks!
Paulo Sherring.

[Günter Pütz]

Hi Paulo,
the framer is also active when no display is connected. You can see that in the cape manager.
A full description on how to find out the usage by the cape manager and how to disable the framer is here:
https://groups.google.com/forum/#!searchin/beagleboard/disable$20hdmi$20gpio/beagleboard/1dluTWZ5AEA/Ddzm6aWCPF8J

But be aware of the pullup/pulldown resistors connected to the port pins on header P8 (see schematic sheet).

[Paulo Sherring]

Gunter (Sorry for the typo, not using good behaved keyboard), thanks for your reply!

Since I am on 3.14, i have no capemgr to make sure it is really not loaded. I am not sure if I completely got your idead, but the framer being active or not should not pose an issue, the big problem is if its driver is sending data over GPIO2. Also, I don't know where the real uEnv.txt file is stored in my eMMC.

Here is the output of lsblk:

mmcblk0boot0 179:8    0     2M  1 disk
mmcblk0boot1 179:16   0     2M  1 disk
mmcblk0      179:0    0   3.6G  0 disk
├─mmcblk0p1  179:1    0    96M  0 part
└─mmcblk0p2  179:2    0   3.5G  0 part /

mmcblk0p1 is a partition that gets mounted as storage when i plug the board over USB and I don't know if those mmcblk0boot* have a filesystem or not (raw data?), all I know is that I can't mount them with mount /mmcblk0boot0 /mnt/bp0.

Any other thoughts on this?

Thanks again!
Paulo Sherring.

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