LCD screen brightness/contrast
#1
Hi,

Just wondering if there is any configuration tweak to increase the brightness/contrast of the 7"LCD panel?

BR.

-Marius--
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#2
Facing same problem here. Brightness and contrast too low, but my LCD came with vertical stripes, usually should be dead pixels but unfortunately it is broken (dead stripes).
I will post a video so you can have an idea if you have the same problem. I have read somewhere ( i can't remember where ) it is a back-light issue so it seems just a matter of turning the back-light on.
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#3
Learnincurve, please see if you have similar problem. The odd thing is that the stripes are really bright and the purple background color on Unity greeter cannot be seen.

What you see here is is TSLIB and X11 in action (please turn off sound): https://drive.google.com/open?id=0B7A7OP...URhemlOT0U
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#4
(02-10-2017, 08:21 AM)Learnincurve Wrote: Hi,

Just wondering if there is any configuration tweak to increase the brightness/contrast of the 7"LCD panel?

BR.

-Marius--

Don't know about the contrast but this turns the brightness up to 100% for me:

Code:
# echo 362 > /sys/class/gpio/export
# echo out > /sys/class/gpio362/direction
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#5
(02-10-2017, 06:58 PM)psychedup Wrote:
(02-10-2017, 08:21 AM)Learnincurve Wrote: Hi,

Just wondering if there is any configuration tweak to increase the brightness/contrast of the 7"LCD panel?

BR.

-Marius--

Don't know about the contrast but this turns the brightness up to 100% for me:

Code:
# echo 362 > /sys/class/gpio/export
# echo out > /sys/class/gpio362/direction

Thanks, this helped to find the thread, it is from pfeerick: http://forum.pine64.org/showthread.php?tid=2896

I think  you must write some value to the pin to make it work as in the thread. seems not.
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#6
Thanks!

I don't have any vertical stripes on my screen, but the 362 out tweak did the trick!


Screen is nice and bright now!

BR.

--Marius--
  Reply
#7
Turning up to full brightness and turning off work well, by following:
# echo 362 > /sys/class/gpio/export
# echo out > /sys/class/gpio362/direction (turns up to full)
# echo in > /sys/class/gpio362/direction (turns off backlight)

I can also turn on and off by echoing:

# echo 0 > /sys/class/gpio362/value (turns on)
# echo 1 > /sys/class/gpio362/value (turns off)

but, when the system boots without manipulating these, the backlight is on, but dim. I can't find a way of reverting to that after doing the first:

# echo out > /sys/class/gpio362/direction

pfeerick 's thread seems inconclusive on other values.
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#8
The pin that controls the backlight is actually a hardware PWM output. If you program the PWM or use a linux backlight driver that supports GPIO-PWM you should be able to control brightness like on the Android images.
Come have a chat in the Pine A64 IRC channel >>
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#9
Thanks, will look into it. Out-of-the-box the pin is obviously being fed by PWM control. Can you point to where this is configured and turned on at boot?

BR.
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#10
For the BSP (3.10.x) kernel the PWM output (PL10 according to the schematics) is afaik tied to the LCD driver and there should be some controls in the /sys/ filesystem.

If you look at the device tree:

Pin Config:
https://github.com/longsleep/build-pine6...4.dts#L776

LCD Entry seems to have values too:
https://github.com/longsleep/build-pine6....dts#L1965

PWM Driver entry, from the pinctrl phandle:
https://github.com/longsleep/build-pine6....dts#L2071
from the compatible line it should be tied to a driver called "sunxi-pwm16"
Come have a chat in the Pine A64 IRC channel >>
  Reply


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