GPIO pin of BBB stuck on 'high' no matter the 'value'

Hello everyone,

I apologize if this is not in the right section, this is my first post.
I am trying to learn linux and embedded linux programming and I am playing with my newly arrived BBB.

After reading a bit I am trying to do a simple startup exercise by trying to control an LED by writing into /sys/class/gpio/gpiox/value ‘file’.

I have connected an LED and a resistor on pin #3 of P8 connector of my BBB.

According to the BBB usermanual pin#3 of P8 connector is gpio1_6 so, as I understand it the number of this GPIO in software(in the /sys/class/gpio folder should be 38: 1x32 + 6).

So I assumed this pin should be controlled by writing into the file located at /sys/class/gpio/gpio38/value

This is the output from the terminal(I am checking to see if the pin is configured as output then I am trying to write 1 and 0 into the value file to control the LED):

debian@BeagleBone:/sys/class/gpio/gpio38$ cat direction 
out
debian@BeagleBone:/sys/class/gpio/gpio38$ echo 1 > value
debian@BeagleBone:/sys/class/gpio/gpio38$ cat value
1
debian@BeagleBone:/sys/class/gpio/gpio38$ echo 0 > value
debian@BeagleBone:/sys/class/gpio/gpio38$ cat value
0
debian@BeagleBone:/sys/class/gpio/gpio38$

From what I can tell everything fine here. However my LED stays on no matter what I do.

This is how I connected the LED on the board:



The green wire is connected on pin3 of P8 which I am trying to control as an output. Then goes into the resistor then into the anode of the Led. The white wire is connected on pin 2 of BBB which should be GND if I understood the schematic correctly and that goes into the anode of the LED.

Please help me understand why the LED is not being controlled as I expected.
Considering the hw wirings are correct, I am assuming I have done a mistake when trying to identify the number the kernel uses to refer to this pin? So when I am writing to pin 38 am not actually controlling gpio1[6] as I expected?
I assume that is the mistake but from what I understood from the materials I’ve read gpio1[6] should be 1x32+6 in software=38.

Please help me understand where I am wrong. Thank you!

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From what I understand, the BBB eMMC pins are taken up by that pin…

A way around that issue is to go into /boot/uEnv.txt and uncomment the overlay for the eMMC.

Warning

If you are using the eMMC on the BBB, do not uncomment that line as it will hold your BBB useless unless using a micro SD Card.

Seth

Hello. Thank you for the answer. Yes I think that is it. I was under the impression that the column name here indicates how the pins are configured by default:


So I assumed that P8_3 should be a GPIO since it has ‘GPIO1_7’ under Name column. But maybe that means at booting.

I switched to using P8_11 and now everything works fine.

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