Hyperpixel4 - Disable backlight on shutdown


#1

Hi guys,
I’m using the fantastic Hyperpixel4 with my Retropie and I was wondering if it could be possible to disable the backlight when issued the “shutdown”.

I read about the clean-shutdown (https://github.com/pimoroni/clean-shutdown) script but I don’t know if and how I can use it for my purposes.

I have an Rpi3B+ and the Hyperpixel4, no other Hat (or Hack3rHat).

Thanks a lot


#2

I’m not 100% sure whether the Pi will hold a pin state in shutdown.

Since HyperPixel4 has a pull-up resistor that defaults the backlight to “on” (call it a failsafe if you will) the Pi would have to actively pull the pin down to counter-it.

You could try adding the following to your /boot/config.txt -

dtoverlay=gpio-poweroff,gpiopin=19,active_low=1

#3

Thanks Gadgetoid, I tried and it works like a charm!

Many thanks!


#4

Wooohoo! It was an educated guess at best, I’m glad it works.


#5

I have used your trick in the “dual-boot” thing suggested here in this thread: Hyperpixel - selective output (eg on boot)?

I’ve added the dtoverlay string in both config files but when I’m using the HDMI obviously the HyperPixel backlight is still on because it didn’t receive the “shutdown” command. Is there a way I can shutdown the HyperPixel4 or the backlight if I’m using the HDMI output?

Furthermore, is it possible to adjust the brightness, contrast and similar?

Thanks and sorry for all the questions.