Am Montag, den 15.10.2018, 11:37 +0200 schrieb H. Nikolaus Schaller:
Hi,
The frequency is set WAY too low right now, same for the keyboard LEDs. It can be set in the pyra-mainboard-v5.0.dtsi. You can find it searching for "pwm-backlight".
It says 12000000 which is 12ms period/83Hz I suppose. Any idea how/why the current value was chosen?
1/50 is too slow and makes flicker visible to everybody. higher values have the problem that the converter does not reach 100% of the theoretically possible maximum brightness the closer it comes to 1/500. If you go beyond ca. 1/150 you will already notice that.
Well, I do notice flickering up to 120Hz on CRTs, so it should still be higher than 82Hz :)
I think the "common" 175Hz that normal monitors use, should be good.
This is an interaction between PWM and the DC/DC converter which needs ca 1ms to start to illuminate the panel.
Well, is it theoretically possible to change the frequency based on brightness? With maximum brightness, even with 83Hz, flickering is barely visible (I guess because the LEDs also have some fall-off time), but with lower brightness, it gets worse.
So maybe for full brightness 100Hz so that we reach full possible brightness and for various lower brightness values higher frequencies.
I'm happy to test different values and deliver the perfect frequency values depending on the brightness.
It could be the magnet in the lid is too weak - but I had no idea how I could test the lid switch, so couldn't check that.
You can use evtest, pyra_test_inputs should also support it.
I tested with evtest.
Okay, if that is confirmed to be working, I'll use it as test as well.