Comments on: Chapter 16: Embedded Kernel Programming

By: Brett

Brett — Wed, 11 May 2016 17:00:28 +0000

Excellent addition, very great read. Might have to use soon as well: has anyone else noticed that P9_15 AKA GPIO_48 has stopped responding after updating to the latest 8.3 kernel? I’ve been using that pin as a toggle for months but this kernel broke the function for reasons I cannot discern. An LKM may fix it.

By: Derek

Derek — Tue, 30 Jun 2015 10:32:51 +0000

In reply to Fointard. Hi Fointard, my guess is that the device tree overlay notes exclusive use of these pins with GPIO-LEDs and therefore when you use them in your module the requests appear. You would probably have to disable the GPIO-LEDs entry in the DTS for the BBB and then it would be fine (see Chapter 6 and Chapter 3). Kind regards, Derek.

By: Fointard

Fointard — Sun, 28 Jun 2015 16:56:34 +0000

Hi Derek,
I’ve been trying to get an LED kernel driver running on my BBB but i’m always getting an error when trying to access the pins :

[ 195.251541] gpio_request: gpio-53 (sysfs) status -16
[ 195.251569] gpio_request: gpio-54 (sysfs) status -16
[ 195.251593] gpio_request: gpio-55 (sysfs) status -16
[ 195.251617] gpio_request: gpio-56 (sysfs) status -16

I think -16 stands for EBUSY which is not weird because the default LED kernel driver is actually using the pins (default heartbeat when we boot the board etc…). My driver actually works and make the LEDs blink but I don’t think this is a clean way to do it.

What i’d like to know is this : how can I disable the default LED kernel driver so that I don’t get this error and the pins are unsused when I request them ? I think I might have to rebuild a custom kernel or mess with the device tree but I just don’t know where to start. Can you help ?

PS : my code is on GitHub : https://github.com/Fointard/SLD

By: Derek

Derek — Fri, 26 Jun 2015 20:48:06 +0000

In reply to David. Hi David, No HDMI is not required for flashing -- see the guide in Chapter 2. Kind regards, Derek.

By: David

David — Thu, 25 Jun 2015 17:00:41 +0000

In reply to Derek. Do I need the HDMI for flashing? or can I just reinstall debian and work with it?

By: David

David — Thu, 25 Jun 2015 04:52:16 +0000

In reply to Derek. thank you Derek Ill have to buy it because I disabled the HDMI for pwm outputs and...

By: Derek

Derek — Wed, 24 Jun 2015 12:51:38 +0000

In reply to David Rodriguez. Hi there, on solution is that you can use the USB UART TTL 3V3 cable that is described in Chapter 1 to connect to the BBB and ensure that the sshd is running. Alternatively, you could attach a monitor, keyboard, mouse and do the same. Kind regards, Derek.

By: David Rodriguez

David Rodriguez — Tue, 23 Jun 2015 16:09:42 +0000

Hello Derek, I have a problem with my beaglebone I installed via ssh an rt kernel using rsync and after the reboot my beaglebone refuses ssh connection how can I fix this?

By: Derek

Derek — Fri, 29 May 2015 21:51:46 +0000

In reply to Rakesh K. I don't think that is possible.

By: Rakesh K

Rakesh K — Fri, 29 May 2015 06:34:43 +0000

Hi,
how can i do debugging in kernel for ADC using eclipse luna.