Balena Train monitor GPIO already in use


I’ve set up the Raspberry Pi Train monitor per the tutorial at

However I’m getting a GPIO warning on start up and the display is not showing anything.

I’ve turned on support access for the application and the UUID is eff6cf9888fdb7002a7348a7c41cfe9b


Hi Gregor,
I am wondering if this might be something left over from a previous run that did not terminate properly. Have you tried rebooting the device ?
Regards Thomas


I tried rebooting, it seems to have cleared the error from the logs but the screen is still not showing anything.

I tried restarting the container but this then caused the GPIO error again

OK, that sounds like the error is not directly connected to the GPIO already in use error but rather to something else failing and the GPIO error might just be due to the service not shutting down properly. I will take a look at the device…

Nothing sticks out other than that you are using 64bit OS on your RPI3. I have seen some issues come up with 64bit OS on RPI4 and to be honest I have not encountered a 64bit RPI3 on support at all yet.
I would recommend re-checking your connections to make sure you have got that right and maybe trying to re-flash with the regular balena (32-bit) and retrying with that.
If the above does not get you going, I will forward this to the maintainer and see if he has any ideas…

I can’t see an option for Raspberry pi 3 32bit on the new device section of my application. It appears to only be either 64bit or Rasberry pi 4 images available

Hi Gregor, that is because you created the application with default type Raspberry Pi 4. If you create a new app with default type Pi 3 for example you will be able to ad Pi 3 32 or 64, and Pi 4 too. It’s always better to go for the lowest arch denominator.

In any case, can you share the exact error you are getting? I tried poking around but support access seems to have expired. Have you checked your GPIO connections? I know I’ve lost many hours due to not paying enough attention.

That makes sense, I’ll create a RPI 3 Application justnow and make a 32 bit image.

Sounds good, let us know how it goes!

Hi I set up the RPI3 application and still didnt get anything.

I had a funny feeling the pins weren’t working quite right on my Pi 3 before so I set up a Pi Zero W application and tried it on my Pi Zero but still nothing.

I bought the OLED screen from Ali Express that was linked in the tutorial so shouldnt be a hardware issue.

I’ve re-checked my wiring but it appears to be correct.

I’m not sure what my next steps are.

Hi Gregor,
I am wondering if there is an easy way to test your setup independently from balena and the train sign project. Have you seen your screen display anything at all ?
My next step at this point would be to try a basic setup to display some arbitrary text on the screen. Do you have any instructions that came with the screen or maybe a simple python app to display some kind of hello world ?
If you have nothing of that kind I can contact the maintainer - he might be able to supply a simple test script to ensure the hardware is working.

That’s a good idea, I’ll make up a raspbian image and see if I can write something to the screen with my own python script. I’ll let you know how I get on.

@GregorR hey there, project author here - thanks for giving it a try. I wonder if you remembered to make the change on the back of the display to put it in the right mode? It’s in the guide but may not stand out enough - see below:

Hi Chris,

Must’ve missed this in the instructions - I’ve removed the R6 and put a 0 Ohm resistor in R5.

I’ll let you know how it goes.


This solved the issue. Thanks for your help - in the future I’ll make sure to read the instructions properly to avoid embarrassing mistakes like this!!

Thanks again.

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@GregorR you’re welcome, I updated the post to make it a bit more obvious. If you have any photos of your build when it’s finished we’d love to see them :slight_smile:

Brilliant, I’ll make sure to send some photos once I’ve made a case to house it all. Cheers

That would be awesome! Please do share :slight_smile: