BBB LCD3 Cape and inactivity

[Colin Bester]

I have a beaglebone black with lcd3 cape installed and all appears find on startup.

After a while of inactivity, the displays appears to go into some form of sleep or screen saver mode but backlight stays on. i.e., The normal GDM screen with background and icons switches to an all white display (just backlight).

Is anyone else experiencing this?

I would expect the backlight to switch off as well.

Cheers

Colin

[Daniel Metcalf]

Yes, I have experienced it and am still working on a solution.

Dan

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[Colin Bester]

Was wondering if you have come up with any further solution? I can write '0' to backlight brightness but while this dims the display significantly it doesn't switch if off.

[John Syn]

From: Colin Bester <bester...@gmail.com>
Reply-To: <beagl...@googlegroups.com>
Date: Monday, May 26, 2014 at 4:54 PM
To: <beagl...@googlegroups.com>
Subject: Re: [beagleboard] BBB LCD3 Cape and inactivity

Was wondering if you have come up with any further solution? I can write '0' to backlight brightness but while this dims the display significantly it doesn't switch if off.

Have you checked that EHRPWM1A is low when you dim the display? Here are two files that will control the backlight.

/driver/video/backlight/pwm_bl.c

/driver/pwm/pwm-tiehrpwm.c

Regards

John

On Thursday, December 19, 2013 3:07:52 PM UTC-6, Daniel Metcalf wrote:

Yes, I have experienced it and am still working on a solution.

Dan

On Dec 19, 2013 11:03 AM, "Colin Bester" <bester...@gmail.com> wrote:

I have a beaglebone black with lcd3 cape installed and all appears find on startup.

After a while of inactivity, the displays appears to go into some form of sleep or screen saver mode but backlight stays on. i.e., The normal GDM screen with background and icons switches to an all white display (just backlight).

Is anyone else experiencing this?

I would expect the backlight to switch off as well.

Cheers

Colin

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[Colin Bester]

Thanks John, I will look deeper into this.I have actually just switched over to debian OS and will test.

One test I did do today was to write a zero ‘0’ to brightness by executing "echo 0 > /sys/class/backlight/backlight.11/brightness"

This did reduce the brightness but didn’t take it to zero light but does dim the display. Likewise a 50 is brighter and 100 is brightest.

I am not sure if this is related in any way at all but will look more tomorrow.

Cheers and thanks
Colin

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[John Syn]

On 5/26/14, 7:20 PM, "Colin Bester" <bester...@gmail.com> wrote:

>Thanks John, I will look deeper into this.I have actually just switched
>over to debian OS and will test.
>
>One test I did do today was to write a zero '0' to brightness by
>executing "echo 0 > /sys/class/backlight/backlight.11/brightness"

When you write to ³brightness², which is defined as a sysfs attribute in
/driver/video/backlight/blacklight.c line 247

This calls ³backlight_store_brightness² on line 148. You can add a few
printk statements to understand what is happening or read up on Dynamic
Debugging which you will find in /Documents/dynamic-debug-howto.txt

Regards,
John

[Colin Bester]

John, did you mean to attach files or are they available in a download bundle?

[John Syn]

From: Colin Bester <bester...@gmail.com>
Reply-To: <beagl...@googlegroups.com>

Date: Tuesday, May 27, 2014 at 6:29 AM

To: <beagl...@googlegroups.com>
Subject: Re: [beagleboard] BBB LCD3 Cape and inactivity

John, did you mean to attach files or are they available in a download bundle?

These are files in the Linux kernel. Use this wiki to download the Linux Kernel.

http://eewiki.net/display/linuxonarm/BeagleBone+Black

Regards,

John

[Colin Bester]

I just managed to get around to looking a little deeper into this and connected an oscilloscope to EHRPWM1A (which I figure is pin P9_14) and confirm that when writing a zero to brightness (using echo 0 > /sys/class/backlight/backlight.11/brightness) that the pin is low. Likewise write a ’50’ sets a 50% duty cycle and LCD brightens. I haven’t set up environment to compile and test using ‘c’ files yet.

With low on pin P9_14 the LCD is still visible.

With debian version I now have running, I have not seen the LCD goto sleep yet - still have to look into this.

~C

On May 26, 2014, at 8:03 PM, John Syn <john...@gmail.com> wrote:

[John Syn]

From: Colin Bester <bester...@gmail.com>
Reply-To: <beagl...@googlegroups.com>

Date: Thursday, May 29, 2014 at 6:45 AM

To: <beagl...@googlegroups.com>
Subject: Re: [beagleboard] BBB LCD3 Cape and inactivity

I just managed to get around to looking a little deeper into this and connected an oscilloscope to EHRPWM1A (which I figure is pin P9_14) and confirm that when writing a zero to brightness (using echo 0 > /sys/class/backlight/backlight.11/brightness) that the pin is low. Likewise write a ’50’ sets a 50% duty cycle and LCD brightens. I haven’t set up environment to compile and test using ‘c’ files yet.

With low on pin P9_14 the LCD is still visible.

In that case this is a hardware issue. P9_14 is connected to the enable pin of the LED backplane driver so the leds should turn off. 

Regards,

John

With debian version I now have running, I have not seen the LCD goto sleep yet - still have to look into this.

~C

On May 26, 2014, at 8:03 PM, John Syn <john...@gmail.com> wrote:

From: Colin Bester <bester...@gmail.com>
Reply-To: <beagl...@googlegroups.com>
Date: Monday, May 26, 2014 at 4:54 PM
To: <beagl...@googlegroups.com>
Subject: Re: [beagleboard] BBB LCD3 Cape and inactivity

Was wondering if you have come up with any further solution? I can write '0' to backlight brightness but while this dims the display significantly it doesn't switch if off.

Have you checked that EHRPWM1A is low when you dim the display? Here are two files that will control the backlight.

/driver/video/backlight/pwm_bl.c

/driver/pwm/pwm-tiehrpwm.c

Regards

John

[Colin Bester]

I’d agree except I am seeing it with two different LCD modules BB-View and Cape LCD3 & LCD4 - different designs, different circuit, different manufacturer.

I’ll have to noodle on it.

~C

On May 29, 2014, at 1:42 PM, John Syn <john...@gmail.com> wrote:

From: Colin Bester <bester...@gmail.com>
Reply-To: <beagl...@googlegroups.com>
Date: Thursday, May 29, 2014 at 6:45 AM
To: <beagl...@googlegroups.com>
Subject: Re: [beagleboard] BBB LCD3 Cape and inactivity

I just managed to get around to looking a little deeper into this and connected an oscilloscope to EHRPWM1A (which I figure is pin P9_14) and confirm that when writing a zero to brightness (using echo 0 > /sys/class/backlight/backlight.11/brightness) that the pin is low. Likewise write a ’50’ sets a 50% duty cycle and LCD brightens. I haven’t set up environment to compile and test using ‘c’ files yet.

With low on pin P9_14 the LCD is still visible.

In that case this is a hardware issue. P9_14 is connected to the enable pin of the LED backplane driver so the leds should turn off. 

Regards,

John

[aahi...@gmail.com]

Hi there folks,

The CircuitCo LCD3 cape version A2 basically pulls up the backlight supply enable line via R126.  By removing R126, and adding a 0R resistor (or a blob of solder) on the pads for R123, you enable use of the EHRPWM1A line to control the backlight.

The caveat is that when you power up the BBB, you should issue a

echo 50 > /sys/class/backlight/backlight/brightness

to have anything come up on the BBB LCD3.

Cheers!



- Antonio

[Colin Bester]

Thanks!

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[femy.v...@gadgeon.com]

how to come out of sleep mode ? Is it possible by any commands ?