Q Light Controller+

Hello-

Apologies in advance for novice questions.. I have very little experience with Linux and after several hours of fruitless searching on this forum and google I was not able to solve my issue.. so I hope it's ok to ask here.

BACKGROUND:
I have a Pi 400 with a monitor connected via HDMI.

I am attempting to use QLC+ to control a very simple lighting arrangement of 16 dimmers using a DMX King eDMX MAX plugged directly into the Pi's ethernet port. I do not plan to connect to any other network devices.

Following the QLC+ Raspberry Pi Installation guide PDF, I loaded qlcplus_raspios_bullseye_20230519.img to a brand new 64 GB Sandisk micro-SD card using the Raspberry Pi imager on my windows PC.

PROBLEM:

When I attempt to boot from the SD card, it does not appear to load QLC+ and instead asks me for a username and password. I entered the default "pi" and "raspberry" and received a command prompt.

I entered "qlcplus" to attempt to run the software and received the following error:

qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem. 

I attempted to manually reinstall the xcb plugin but that failed as well.

QUESTIONS:
Any ideas what may be causing this issue?
Does the Pi need to be connected to the internet?
Was I supposed to do anything with the .deb and .md5 files provided in the download area?

Thank you for any assistance.

Nate

Hi Nate, QLC+ on the Raspberry Pi doesn't use the XCB output (which requires an X.org instance to work)
Instead it uses an output called EGLFS. It's all in the startup script provided in the image which is located in so basically the minimum command line would be

Massimo-
Thanks for the quick response! I tried the last command you suggested and it gave me a bunch of new errors, with the most helpful one being "Failed to move cursor on HDMI1: -13". That prompted me to swap the HDMI cable to the other port on the back of the Pi 400. After doing that, QLC+ started up perfectly from boot with no troubles! Just wanted to provide that feedback in case others run into a similar issue.

Are there any existing tutorials or threads that discuss using QLC+ on a standard OS image (that includes the linux GUI)? My rough understanding is that this would permit QLC+ to operate more like it does on a PC, easier to manipulate for developing a virtual console, but will run more slowly given that it's not optmized for QLC+ like your custom image is. I'd be interested to try it if it's not too difficult. I figured since my lighting application is extremely simple maybe running slowly isn't a huge concern.

Thanks again,

Nate

nkb5f wrote: ↑Wed Jan 03, 2024 3:46 pm Are there any existing tutorials or threads that discuss using QLC+ on a standard OS image (that includes the linux GUI)? My rough understanding is that this would permit QLC+ to operate more like it does on a PC, easier to manipulate for developing a virtual console, but will run more slowly given that it's not optmized for QLC+ like your custom image is.

The installation is described in chapter 10 of the PDF manual.
You need the .deb file (debian package) and you install it like any debian package.

Your guess is correct, with the package you'll have normal Raspi desktop (raspbian/ubuntu/whatever you choose) and QLC+ like on a PC.
You will see if the speed is OK for you or not.

If you choose non-debian based distribution (redhat, fedora, gentoo,...) you'll have to compile QLC+ on your own. It more complicated than just an installation, but can be done.

@Massimo, you may simplify the section to:

1. download the file: wget xxx.deb
2. install the package and its dependencies: sudo apt install ./xxx.deb, the ./ part is important.

(I've not tested it, it's normal debian/ubuntu way of installing local packages).

Jano

Thank you for the helpful details, Jano.

When I select the OS to image, does QLC+ prefer to run on a 32-bit or 64-bit OS (or does it not matter)?

Nate

On Raspberry Pi QLC+ runs on 32bit