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+--- Thread: Screen brightness and PWM (/showthread.php?tid=9041)
Screen brightness and PWM - hex - 02-06-2020
Hi,
Any hardware devs able to answer this?
Basically, does the display on the PinePhone use PWM to control brightness?
I hope not! But if so, what's the duty cycle?
Looking at the DTS, it seems it uses Linux kernel's PWM driver(?) to adjust brightness, does that imply PMW at the hardware level or not neccessarly?
Thanks.
PS: Whilst at it, how about the PineTab?
RE: Screen brightness and PWM - VaZso - 02-06-2020
(02-06-2020, 06:35 AM)hex Wrote: I hope not! But if so, what's the duty cycle?I think you would like to ask about it's frequency rather than duty cycle.
RE: Screen brightness and PWM - hex - 02-06-2020
(02-06-2020, 08:01 AM)VaZso Wrote:(02-06-2020, 06:35 AM)hex Wrote: I hope not! But if so, what's the duty cycle?I think you would like to ask about it's frequency rather than duty cycle.
Correct, can't edit it tho
RE: Screen brightness and PWM - wibble - 02-07-2020
Not necessarily - see the schematic. I've not found an english datasheet for the AP3127B025 listed, but you can buy them on alibaba for 3 cents.
RE: Screen brightness and PWM - hex - 02-11-2020
Okay, I looked at the schematics it didn't help, its beyond me!
The good news is phone is arriving Thurs, and I have a slow mo digi cam, I'll test it and report back.
Thanks.
I've found the datasheet if anyone is interested: http://files.remont-aud.net/baza/dc_dc/data/AP3127B.pd
RE: Screen brightness and PWM - wibble - 02-11-2020
Thanks for the datasheet. The chip isn't being used quite as the datasheet suggests, but the end result should be similar - the pwm signal is low pass filtered and used to control the current in a switch mode current source that's switching at ~1MHz. I don't know the pwm frequency and haven't done the calcs for the filter, but brightness ought to vary a lot less than if it were straight PWM of LEDs.
RE: Screen brightness and PWM - hex - 05-19-2020
Okay, I can confirm.
Using a 1000FPS capable camera, I can confirm there is no blacklight flicker whatsoever, so it's good news, I hope the tablet will be equally so.