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
Yes, I have experienced it and am still working on a solution.
Dan
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.
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
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
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
John, did you mean to attach files or are they available in a download bundle?
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
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
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
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
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!
Thanks!
how to come out of sleep mode ? Is it possible by any commands ?