Q Light Controller+

Hallo
Yesterday i got the link for installation of qlcplus on Pi
i have prepared the SD Card according to the PDF Instruction.
but its not starting qlcplus.
I am using Pi B
HDMI Monitor connected to HDMI Port
LAN Connection for Internet
USB Mouse and Key Board
I am getting the following error message:
sudo qlcplus
qt.qpa.screen: QXcbConnection: Could not connect to display
Could not connect to any X display.

I have visited all these links, followed the suggested
editing of the config file but still its not working.

viewtopic.php?f=7&t=13854
viewtopic.php?f=7&t=13940
viewtopic.php?f=7&t=14093
viewtopic.php?f=7&t=14006

can any body please help me?

Hi, are you using the full provided image or have you just installed the Debian package?

hallo,
Thanks for your reply
i am trying to install the full image.

regards
Maity

the right command to launch QLC+ on the official image is

Hallo,
tried this also but still its not starting.

Maity

My setup is a bit different, so I'm not sure how much help I'll be, but a few things to try:

Open up a command line/terminal window and run It should hopefully come back with something like ":0" or "localhost:0", or maybe "localhost:10.0"

I'm assuming you are already using a GUI interface on your Pi, so the command above should show you something. Another thing to try would be to run qlcplus manually, without using 'sudo' before it.

I have to imagine that with this failure being so early in the program execution, adding the "-d 3 --log" flags with running qlcplus won't help at all. But if you get past this current error, it could be helpful if you're still seeing problems.

FYI, my setup is a headless (no mouse/keyboard/display) Pi 2B running a manually complied QLC+ using VNC so I can access the GUI remotely. As part of the VNC server startup, it automatically executes

Hi all,
Thanks for your prompt reply. I still haven't been able to root cause the issue. But I made a few observations:

• I tested the image qlcplus_raspbian_buster_20190825.7z on my friend's RPI 4, and it worked seamlessly. However, the same process fails on my RPI 1 Model B. Thus, this might be an issue with older PI hardware.
• After Pi boots, I ran the following command:

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  sudo service qlcplus status

  , and it generates the following output:

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  ● qlcplus.service - LSB: Q Light Controller Plus
     Loaded: loaded (/etc/init.d/qlcplus; generated)
     Active: active (exited) since Sun 2020-05-17 03:08:08 BST; 21min ago
       Docs: man:systemd-sysv-generator(8)
    Process: 293 ExecStart=/etc/init.d/qlcplus start (code=exited, status=0/SUCCESS)
  
  May 17 03:08:05 raspberrypi systemd[1]: Starting LSB: Q Light Controller Plus...
  May 17 03:08:07 raspberrypi qlcplus[293]: Starting Q Light Controller Plus: qlcplus.
  May 17 03:08:08 raspberrypi systemd[1]: Started LSB: Q Light Controller Plus.
  

• Even if I run

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  sudo service qlcplus start

  , nothing happens.

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  ps aux | grep qlcplus

  produces no output either.
• I further tried setting

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  export DISPLAY=:0

  , and then launching qlcplus manually, but still get the error

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  qt.qpa.screen: QXcbConnection: Could not connect to display :0
  Could not connect to any X display.

I think there might be a config issue for the buster image for older PI versions. The .deb version works fine if I install it manually on a clean raspbian image. However, I would like to make use of the optimized image if possible.

Thanks for all your help,
Stay safe!
Santanu

Hi Sanatu,

qlcplus should be starting automatically as already mentioned. As per the manual for the RPi image there is not X server included in the image:

Powered by Qt 5.11.3 directly running on OpenGL for fast 2D rendering of the User Interface. Xorg is not present in the image.

So you cannot start the qlcplus binary directly like you do. You could try adding --log to the QLCPLUS_OPTS in the /etc/init.d/qlcplus file and see if some clue shows up in /root/QLC+.log.

Is your RPi getting an IP address? Because qlcplus starts default with the web interface enabled I can imagine it has trouble starting without an IP for the system.

What does the command journalctl say?

Hello

are there any new findings? because i have the same problem too. It works with the old image(20190825) but if I use the new image(20200830) QLC dont start.

Best wishes, Luca

I have the same problem.
Web interface works perfect.

I have only tried the newest firmware.

Guys, Pi 1 model is quite old now and I'm not sure if it even makes sense to support it furthermore.
There might be issues with the graphics stack, since there's been a lot of development going to access the GPU from standard Mesa packages.
I have one myself but I don't have much chance to do tests. At the moment I have major network issues that I can't solve. Will be solved in a couple of months, when I move (again) to a new house.