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BB GPIO unable to unexport gpio
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BB GPIO unable to unexport gpio

by smbrandonjr on Thu Oct 11, 2018 12:48 am

I want to use gpio0_30 for something in an app I have written. I am unable to unexport the gpio, but can export/unexport others...

I am using a Beaglebone Black, running:

dogtag:[BeagleBoard.org Debian Image 2017-03-19]
bootloader:[/dev/mmcblk0]:[U-Boot 2017.03-00002-gd12b1519b4]
bootloader:[/dev/mmcblk1]:[U-Boot 2018.03-00002-gac9cce7c6a]
kernel:[4.4.54-ti-r93]
nodejs:[v4.9.1]
Attachments
gpio-issue.PNG
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smbrandonjr
 
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Re: BB GPIO unable to unexport gpio

by drewfustini on Fri Oct 12, 2018 6:34 am

This version is u-boot bootloader on the eMMC is too old.

Please run this command on your BeagleBone to disable the old version of the u-boot bootloader on the eMMC:
sudo dd if=/dev/zero of=/dev/mmcblk1 bs=1M count=10

This will cause the newer u-boot bootloader on the SD card to be used.

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Re: BB GPIO unable to unexport gpio

by smbrandonjr on Fri Oct 26, 2018 9:27 pm

Hi,

Thank you for this step. I am just now able to get around performing it and it got me where I needed to be. Thank you.

I am new to beaglebone and am curious if I will be able to use gpio0_2, gpio0_3, gpio0_4, and gpio0_5 or will those always be reserved for eMMC?

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Re: BB GPIO unable to unexport gpio

by drewfustini on Sun Oct 28, 2018 9:55 pm

if you boot from MicroSD, then you can reuse the eMMC pins.

Here is how to to disable eMMC in the u-boot bootloader:
https://elinux.org/Beagleboard:BeagleBo ... rd_devices

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Re: BB GPIO unable to unexport gpio

by smbrandonjr on Thu Nov 08, 2018 2:08 pm

how can i release these pins so that i may control them?

pins.PNG
pins.PNG (29.55 KiB) Viewed 122 times

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Re: BB GPIO unable to unexport gpio

by drewfustini on Thu Nov 08, 2018 2:51 pm

Please paste the content of /boot/uEnv.txt

I should be able to advise which lines that you should change

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Re: BB GPIO unable to unexport gpio

by smbrandonjr on Thu Nov 08, 2018 3:01 pm

uenv.PNG
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Re: BB GPIO unable to unexport gpio

by smbrandonjr on Fri Nov 09, 2018 3:52 pm

I'd really like to free up as many of the GPIO as possible...I need to be able to use the ethernet adapter and write my OS to the eMMC...other than that, I would like to be able to use it as my own defined input or output if it will be allowed.

gpio-bb.PNG
gpio-bb.PNG (152.74 KiB) Viewed 98 times


Which of these gpio remain available and how do I free them up?

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Re: BB GPIO unable to unexport gpio

by drewfustini on Tue Nov 13, 2018 11:37 pm

I think you have disabled as many of the peripherals as you can, per your uEnv.txt screenshot.

Which pins are you trying to use?

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Re: BB GPIO unable to unexport gpio

by smbrandonjr on Wed Nov 14, 2018 10:31 am

Drew,

Thanks for getting back to me. Until I stumbled across your Twitter, I didn't realize your association to OSHPark. Ironically, the hobby project I'm working on involves a PCB I had OSHPark create for me (very happy with the results). Unfortunately I made some oversights regarding which GPIOs I would have available and need to create a new version of my PCB.

I need to be able to use at least 45 GPIO for my project. I am not married to any specific GPIO except Serial4_RX and Serial4_TX.

Onboard platforms I want to utilize on by BB Black are the eMMC, Ethernet, the Type A USB, and the Mini B USB (my lack of understanding of the BB platform and embedded hardware in general prevents me from understanding whether modifying/utilizing the accessible GPIO with my application would impact any of those onboard devices...well I realize the eMMC platform based on our previous discussions but am unsure on the others)

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Re: BB GPIO unable to unexport gpio

by drewfustini on Tue Nov 20, 2018 3:30 am

smbrandonjr wrote:Drew,
I need to be able to use at least 45 GPIO for my project. I am not married to any specific GPIO except Serial4_RX and Serial4_TX.

Onboard platforms I want to utilize on by BB Black are the eMMC, Ethernet, the Type A USB, and the Mini B USB (my lack of understanding of the BB platform and embedded hardware in general prevents me from understanding whether modifying/utilizing the accessible GPIO with my application would impact any of those onboard devices...well I realize the eMMC platform based on our previous discussions but am unsure on the others)

Hello - I am not certain if it is possible to have 45 GPIOs and eMMC.

I would be a question of the cross section between:
eMMC and HDMI
and
Digital I/O

I would recommend posting on the BeagleBoard.org community mailing list as it has a much wider audience including Jason Kridner (co-creator of the BeagleBone) and Robert Nelson (who creates the Debian images and kernel builds):
http://bbb.io/discuss

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