Comments (7)
from rpi-backlight.
Hey,
Thanks for the quick answer. Yes I'm using the official touchscreen, with its dedicated power supply. Actually it is a cheap phone one so issue might be linked to that as well.
The fact it is in deed a PWM on off method explains half of the problem.
Is there a way to know the commutation frequency somewhere in the code ? If so I will run some calculations to see if freq could be less than 20kHZ for low brightness values.
from rpi-backlight.
Hi guys,
I have pretty much no idea about the physics behind this, but I can forward this to the German Raspberry Pi forum and keep you updated.
from rpi-backlight.
Hey
Thanks that would be great :)
Now that I think about it the answer regarding the PWM freq should be defined in the touch screen firmware.. but it doesn't seem to be open source. Will also continue investigating on my side!
from rpi-backlight.
from rpi-backlight.
You can also try to turn off the backlight:
$ sudo bash -c "echo 1 > /sys/class/backlight/rpi_backlight/bl_power"
Then see if its still emitting that noise.
Make sure you are ssh
into the pi, otherwise it will be hard to turn it back on ;)
echo 0
to turn it back on.
from rpi-backlight.
Well, since this is the rpi-backlight repository you might as well use the Python API for turning the backlight off (which, frankly, uses the same command under the hood) 😂
Response from the forum so far: does it hapenn with another psu as well? Those from phones are made for charging and not stable voltage and usually not recommended.
from rpi-backlight.
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from rpi-backlight.