Sharing docker-compose between Pi2 and Pi3, and accessing serial port

Product support
1

Hi all,

I’ve got an application that’s communicating with hardware over the serial port.

I’ve got two Resinio Starter type Applications, based on the RPi 2 and RPi 3 respectively.

I’m able to get both working independently so they can successfully both receive and send info over the GPIO pins. Awesome!

Now my issue - I’d really like to support both platforms from the same code base.

Here’s an extract from my docker-compose.yml file:

devices:
  - "/dev/ttyAMA0:/dev/ttyAMA0"
  - "/dev/ttyS0:/dev/ttyS0"
  - "/dev/mem:/dev/mem"

I’ve defined some Application Service variables, which I use to override the port connected to - this is great, so I connect to ttyS0 on a Pi3, and ttyAMA0 on the Pi2.

This is all good, except my application won’t start on the Pi2, as it fails with:

no such container -linux runtime spec devices: error gathering device information while adding custom device “/dev/ttyS0”: lstat /dev/ttyS0: no such file or directory '

28.06.18 14:34:01 (+1200) Installed service 'dashboard sha256:6036aa8d1fee8a0b0a90dc05157f2707a2a4e5f1361ee51f2c97d367feef21ae'
28.06.18 14:34:01 (+1200) Starting service 'dashboard sha256:6036aa8d1fee8a0b0a90dc05157f2707a2a4e5f1361ee51f2c97d367feef21ae'
28.06.18 14:34:04 (+1200) Failed to start service 'dashboard sha256:6036aa8d1fee8a0b0a90dc05157f2707a2a4e5f1361ee51f2c97d367feef21ae' due to '(HTTP code 404) no such container -linux runtime spec devices: error gathering device information while adding custom device "/dev/ttyS0": lstat /dev/ttyS0: no such file or directory '

If I remove the ttyS0 devices line in the docker-compose file, the RPi2 works, but the RPi3 doesn’t anymore, as it’s not mapped to the docker container.

Is there a way to make the docker-compose devices mapping conditional or overridden for a given Resinio application, or perhaps use two different docker-compose files? Or is there a way to map docker devices within the Resin.io user interface?

8

Hi,

The raspbian foundation introduced a serial port aliases a while ago. Raspberry Pi 3 serial0 will point to GPIO pins 14 and 15 and use the “mini-uart” aka /dev/ttyS0. On other Raspberry Pi’s it will point to the hardware UART and /dev/ttyAMA0, so where possible refer to the serial port via it’s alias of “serial0” and your code should work on both Raspberry Pi 3 and other Raspberry Pi’s.

You can use this feature on a resin device with resinOS 2.0.2 or higher.

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