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LeMaker 7" LVDS LCD for Banana Pi & Pro

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tkaiser  
Edited by tkaiser at Tue Nov 25, 2014 09:02
mikronauts replied at Tue Nov 25, 2014 08:25
the LCD backlight turned off, however there was still 91mA of current drawn


Can you switch off the backlight / LCD using the aforementioned GPIO approach? Eg. using
  1. gpio export 55 out
  2. gpio export 57 out
  3. echo 0 > /sys/class/gpio/gpio55/value
  4. echo 0 > /sys/class/gpio/gpio57/value
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tkaiser replied at Tue Nov 25, 2014 08:44
Thank you. Just had a look in the fex file for the 7" display:

There it's GPIO pin 57 instead:Wha ...
What do you mean with unstable/flickering? Isn't it enough to switch the pin off?

It's ok for on/off control (not using PWM).
PWM should allow to adjust the backlight with various brightness levels (from 0=off to 255=full on, I believe), but this pin doesn't support hardware PWM. Software PWM works but is CPU dependant, so backlight flickers.
The 2 scripts I linked work well for simple on/off control.

Does that mean that I should switch pin 55 also to 0 when I want to disable the backlight?

I don't think it's necessary.

tkaiser  
Edited by tkaiser at Tue Nov 25, 2014 09:19
HWL_Stouf replied at Tue Nov 25, 2014 09:10
PWM should allow to adjust the backlight with various brightness levels (from 0=off to 255=full on, I believe)


Ah, now I think I understand. According to gpio's manual page the values range from 0 to 1024 by default:
  1. gpio pwm 55 512 # Set pin 55 to PWM value 512 - half brightness
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Ok, time to get hands on such an LCD from LeMaker to play with.

HWL_Stouf & tkaiser,

I'll see if turning off the backlight before a soft shut down will make any difference - but I don't think it will, as the backlight already shuts off when I do a "sudo halt"

My best guess is that the video refresh engine for the LCD is left running after "sudo halt", in which case a driver fix should lower power consumption.

My test desk has another SOC board on it right now, so it will likely be at least tomorrow before I can re-assemble the 7" test and try this.

tkaiser  
Don't hurry please. But would be great to get a clue how consumption will be influenced also when the board is powered on without feeding the LCD controller board and/or the backlight. And since you're able to measure consumption...

BTW: I'm still thinking about something like the ODROID Smart Power but am unsure whether it's worth the price to do some consumption measurements (the ability to store and output values to a connected PC might be very useful to compare other monitoring sources like the AXP209's internal current/voltage values with the PSU's values over time)

Edited by mikronauts at Tue Nov 25, 2014 11:08

that's a cute little device, and somewhat similar to what I've cobbled together - the main difference is that I am using a DVM with RS232 instead of an MCU+ADC

I've been working on setting up one of my RoboPi's to do current/voltage monitoring as part of my never ending lab upgrades.

As there is no hurry I'll finish the SOC review I am working on today before hooking the 7" display back up, after that I'll do power testing on my 3.5" display (time permitting)

cyryllo  

Pasmith  
cyryllo replied at Sun Dec 14, 2014 04:47
http://picoboard.pl/modul-7-calowego-ekranu-lcd-dla-banana-pipro/

woah, GREAT LCDs!!! And The BOARD IS BANANA PRO?????

cyryllo  
Pasmith replied at Sun Dec 14, 2014 07:12
woah, GREAT LCDs!!! And The BOARD IS BANANA PRO?????

Yes it is a Banana Pro

cyryllo replied at Sun Dec 14, 2014 10:43
Yes it is a Banana Pro

I have post it on Media section.

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