VU8m: is it possible to control brightness?

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mad_ady
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VU8m: is it possible to control brightness?

Post by mad_ady »

Hello everyone!

I want to repurpose my m1 + vu8m into a fancy picture frame (+ NAS, VPN, Homeassistant instance, etc) for my parents.

And I've noticed that the screen runs at full brightness, which is too much for a dark room.
I've looked briefly over the forum/wiki, but haven't seen info about brightness control.

Any ideas if it's supported via software?

I hope to have a more thorough look through the dtb/sysfs tomorrow.

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Re: VU8m: is it possible to control brightness?

Post by odroid »

It must be possible since the LED backlight driver IC can be controller by a PWM signal.
Android OS should work out of the box.
Screenshot from 2024-07-08 09-29-35.png
Screenshot from 2024-07-08 09-29-35.png (39 KiB) Viewed 53 times
Check if the GPIO0_C.BIT3 pin is configured as a PWM output.
Let us know which OS image will be used for building a picture frame.

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Re: VU8m: is it possible to control brightness?

Post by tobetter »

@mad_ady, please check the node under /sys/class/backlight/backlight or /sys/class/backlight/backlight1, there is a file brightness that you can echo a value to control the brightness. If you want to set the brightness from booting, you can change the value of it in a device tree overlay file as well.
If it does not work as you expected, please share the version of Linux kernel comes with uname -a.

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Re: VU8m: is it possible to control brightness?

Post by mad_ady »

Ah, thank you both! It's under /sys/class/backlight/backlight/brightness. It wasn't even set to full power, but to 65%. 40% looks better in a regular room.
Funny, that setting brightness level to 1 outputs a perfectly readable image, while 0 turns off the backlight completely!

I won't have a light sensor, but I plan on adjusting brightness manually, or based on time-of-day or by presence detection (I have an ultrasonic sensor hooked up).
So it works just fine, thanks!

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Re: VU8m: is it possible to control brightness?

Post by tobetter »

mad_ady wrote:
Mon Jul 08, 2024 6:17 pm
Ah, thank you both! It's under /sys/class/backlight/backlight/brightness. It wasn't even set to full power, but to 65%. 40% looks better in a regular room.
Funny, that setting brightness level to 1 outputs a perfectly readable image, while 0 turns off the backlight completely!

I won't have a light sensor, but I plan on adjusting brightness manually, or based on time-of-day or by presence detection (I have an ultrasonic sensor hooked up).
So it works just fine, thanks!
It would be wonderful if we see it works with a (ambient) light sensor.

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