Lakka builds on RPi4: some device tree overlays not working

Libretro Lakka
#1

Hi all

Device tree overlays can be used to easily add some extra functionalities to RPi devices via the GPIO pins, without using custom scripts. A power on/shutdown button (gpio-shutdown) and automatic temperature fan control (gpio-fan) can be enabled in Raspbian by just adding some lines to /boot/config.txt.

I tested these device tree overlays with Lakka and found that, using the latest stable release (2.3.2), gpio-shutdown works fine, but gpio-fan does not work. However, when testing the 2020-02-13 nightly build (latest one for RPi4), the situation is reversed: gpio-shutdown does not work anymore, but gpio-fan now works fine…

Can this be fixed with some workaround, so that both DT overlays work?

Best regards

jonas

#2

Hello I am looking for some way to control a fan on Rpi 4b with Lakka 2.3.2 On Rasbian I used this guide and worked fine.

In Lakka it seems it’s not possible. You wrote I can use DT overlays. My fan is controlled by GPIO 17 Is this instruction correct (start at 65C)? dtoverlay=gpio-fan,gpio_pin=17,temp=65000

Then the system should start fan at 65C and turns it off at? Thanks

#3

Hi

Like I wrote before, gpio-fan currently only works with the Lakka nightly builds. It doesn’t work with the current stable version 2.3.2. Why, I have no idea… I was hoping someone from the dev team could have a look at this issue, as dynamic fan control would be really useful.

All DT overlays work in Raspbian. For gpio-fan without any parameters, the fan is switched on at 55 °C and off at 45 °C, so I guess there’s a 10 °C difference.

Regards

jonas

1 Like
#4

Ok Thanks so the python method described in the above link is unuseful… Except if you want to start/stop your fan at desired temperatures.

While the DTOverlay is broken in Lakka stable, do you know if there is some way to control a GPIO with it? I have a multiboot sd card with rasbian and lakka and in rasbian I control the rsap fan with gpio 17, I’ll like to do the same with lakka. I’m not skilled in coding, sorry

Thanks Pietro

#5

Hello

I’m not skilled in coding either… :wink:

Currently, my fan is always on. I use a circuit similar to that in the above link, with fan control wired to GPIO 14, GND and +3.3V. It is switched on by the parameter enable_uart=1 in config.txt, and switched off on shutdown. I don’t run Lakka continuously, so that is enough for me. But of course a dynamic fan control would be way better. Since dtoverlay=gpio-fan works fine in the nightly builds, I suppose eventually we will get it in the stable build.

What puzzles me is why dtoverlay=gpio-shutdown does not work anymore with the nightly builds… Maybe it was forgotten/disabled by mistake.

Let’s hope someone with better technical knowledge of Lakka can have a look at this :slight_smile:

Regards

jonas