Error in opening MATLAB device file for LED trigger source.

Hi, I am using the 'MATLAB support package for Raspberry Pi hardware' using MATLAB 2023a. I have installed all the necessary files on the Pi. I began following the tutorial here:

Getting Started with MATLAB Support Package for Raspberry Pi Hardware - MATLAB & Simulink Example - MathWorks United Kingdom

I got to the first step, ran the code

rpi = raspi('IP Address','username','password');

and was met with the following error (Practice_1 is the name of the script):

Error using Practice_1

Cannot open the device file for LED trigger source.

Any help please? I followed the tutorials accurately on the MathWorks website

[Walter Roberson]

I see a hint that just maybe your raspberry pi might already have a startup program that is using ROS (robot operating system) and so the node might already be busy

https://www.mathworks.com/matlabcentral/answers/463917-error-opening-led-device#answer_888865

This is a bit of a stretch, but it is not impossible.

If something like this were true then removing the startup program should work. Or flip to a new mini-SD memory card and reinstall the operating system.

[Syed Hadi]

I saw that post and tried the steps suggested but it wasn't working. I installed a brande new OS before starting this procedure.

When I try the following in my Pi terminal:

rostopic list

I'm told "bash: rostopic: command not found". This is the same with any other command from that post.

If this is the startup program, it doesn't seem to exist. If that's the case, what's the next step? Any suggestions?

[Walter Roberson]

Sorry, I do not know.

[Joaquin Dillen]

i got the same issue... any news about this??

[Syed Hadi]

Hi, no I haven't got any response, I'm in contact with MathWorks about this, so I'll update this thread once we come to a solution.

[Atakan Aral Ormanci]

I am getting the same error, i have checked the /sys/class/leds directory, it doesn't have led0 led1 led2. This might be causing the problem, i believe it has a function that when matlab is connected to RPi, it uses the leds, but in the connection phase, becouse it doesn't have the led0 activation command in the directory, it doesn't allow the connection.

But its just a guess.

Answer 1

[Syed Hadi]

Hi guys,

I've been in contact with MathWorks support and we've solved this issue.

Basically, if you follow the link below:

Raspberry Pi OS - Wikipedia

You can see a list of OS for Raspberry Pi. MATLAB doesn't support the latest versions of the OS.

What you need to do is follow the link below:

http://downloads.raspberrypi.org/raspios_armhf/images/raspios_armhf-2022-09-26/

And download the file named "2022-09-22-raspios-bullseye-armhf.img.xz".

Then, you can install the OS onto your SD Card using the normal method.

I used balenaEtcher to decompress and flash the OS onto the SD card.

The development team are now aware of this issue and will look into fixing it for future OS.

Hope this helps.

[Beryl Wicaksono]

Hi Syed Hadi,

are you facing ssh certificate issue after installing 2022-09-22-raspios-bullseye-armhf.img.xz? How do you resolve it?

Thanks

[Prasanth Sunkara]

In my opinion using the official Raspberry Pi Imager tool is a better way to setup an image.

https://www.raspberrypi.com/documentation/computers/getting-started.html#using-raspberry-pi-imager

Please ensure you have enabled SSH and assigned proper hostname and user credentials. You may optionally enter the WiFi details as well.

There is an option in the Raspberry Pi imager tool to flash images from your PC too. Towards the end the list

Answer 2

[MathWorks MATLAB Hardware Team]

Hi All,

Follow these steps to resolve the issue,

• Open Raspberry Pi terminal and execute
• $ cd /opt/MATLAB/
• $ sudo pkill mwUnifiedSrvr
• $ sudo rm -rf *
• Download and extract following zip files
• In MATLAB, change your working directory to the above extracted files
• Run >> applyPath.m file
• Create a raspi object in matlab
• >> r = raspi("myAddress",'pi','raspberry');

Thanks,

MathWorks

MATLAB Hardware Team

[Syed Hadi]

I haven't tried this, but I just uploaded the solution I found with MathWorks.

Has anyone else tried this to see if it works?

[Antonios Gementzopoulos]

I have just tried it and it works as advertised.

[Beryl Wicaksono]

This solution is also work. I have tried it.

Answer 3

[Sandin Taci]

Hey @Syed Hadi, try "raspberrypi instead of "raspi":

rpi = raspberrypi('IP Address','username','password')

[Atakan Aral Ormanci]

Hey @Sandin Taci

I just checked and it worked. it says its connected.

But there is still a problem. I just tried the starter kit, but it gives the same error. cannot open or find LED.

[Sandin Taci]

Can you go through these steps again, I guess you skipped a step. Your hardware tab in the Simulink model does not look customized.

https://www.mathworks.com/help/supportpkg/raspberrypi/ref/getting-started-with-raspberry-pi-hardware.html

[Atakan Aral Ormanci]

i just did the steps again and then i realised the problem is with the led.

i then tried to control a servo and it worked.