Pinetime backlight current.
#1
The wiki of the pinetime mentiones the LCD driver part number, but nothing about the part number of the actual display. or backlight. It does mention the 3 backlight pins (low mid high), and according to the schematic these are just connected to a 2k2, a 100R and a 30R resistor, this suggests 3 different brightness levels, but you could get even more brightness levels if you were to combine these 3 brightness levels, but it doesn't really look like that was the intention of the original design. Now I am wondering. Can I pull all these 3 pins low without sending too much current to the backlight?
#2
(03-08-2020, 11:12 AM)TT-392 Wrote: The wiki of the pinetime mentiones the LCD driver part number, but nothing about the part number of the actual display. or backlight. It does mention the 3 backlight pins (low mid high), and according to the schematic these are just connected to a 2k2, a 100R and a 30R resistor, this suggests 3 different brightness levels, but you could get even more brightness levels if you were to combine these 3 brightness levels, but it doesn't really look like that was the intention of the original design. Now I am wondering. Can I pull all these 3 pins low without sending too much current to the backlight?

Hard to say without knowing the spec of the backlight LED!

I decided not to worry about it too much about joining them together. 2k2 is too different from the other values to make much difference to the perceived brightness and the 30R is already pretty bright. Having said that 100R|30R (a.k.a.23R) should be noticable brighter still (if it doesn't break ;-) ).

All in all if you want smoother backlight fades then experimenting with a PWM might be more profitable.
PineTime: wasp-os and MicroPython, Pinebook Pro:  Debian Bullseye
#3
(03-09-2020, 10:19 AM)danielt Wrote:
(03-08-2020, 11:12 AM)TT-392 Wrote: The wiki of the pinetime mentiones the LCD driver part number, but nothing about the part number of the actual display. or backlight. It does mention the 3 backlight pins (low mid high), and according to the schematic these are just connected to a 2k2, a 100R and a 30R resistor, this suggests 3 different brightness levels, but you could get even more brightness levels if you were to combine these 3 brightness levels, but it doesn't really look like that was the intention of the original design. Now I am wondering. Can I pull all these 3 pins low without sending too much current to the backlight?

Hard to say without knowing the spec of the backlight LED!

I decided not to worry about it too much about joining them together. 2k2 is too different from the other values to make much difference to the perceived brightness and the 30R is already pretty bright. Having said that 100R|30R (a.k.a.23R) should be noticable brighter still (if it doesn't break ;-) ).

All in all if you want smoother backlight fades then experimenting with a PWM might be more profitable.

I guess I'll just stay away from turning on multiple backlight pins then and just use PWM. I don't know if any people from pine are watching this forum, but if it is indeed the case that this could damage the display, then it might be nice if that was mentioned on the forums.


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