Add native Linux/Ardulinux repeater target

[l5yth]

This is a continuation of #1137 (and #395) to fix #619. The goal is to keep this diff clean and rebased on upstream so it can eventually be merged into the MeshCore firmware, but I'm also happy to maintain the fork until then.

It adds a linux_repeater PlatformIO environment that compiles the simple repeater firmware for Linux SBCs (Raspberry Pi Zero, 3, 4, 5) using the ArduLinux Arduino-compatibility layer. Compared to #1137, it no longer depends on Meshtastic's Portduino framework, and repeater name/password/etc. no longer need compile-time constants, they're parsed from an INI file on first run and changed thereafter via CLI or remote config.

New files

• variants/linux/, LinuxBoard (SPI + libgpiod GPIO init), LinuxSX1262/LinuxSX1262Wrapper (RadioLib SX1262 driver), target.cpp/h, PlatformIO config, INI templates, systemd unit, and udev rules
• boards/linux.json, board descriptor

Shared-helper changes (guarded by ARDULINUX_PLATFORM)

• IdentityStore, ClientACL, CommonCLI, RegionMap: use the 2-arg fs::open(path, mode) (string-mode, as on RP2040) since the ArduLinux FS has no 3-arg overload
• TxtDataHelpers: use sprintf/PRId32 instead of ltoa (not available)
• MyMesh: filesystem init, formatFileSystem() stub, and saveIdentity() path for Linux; apply INI config as first-run defaults before loadPrefs()

Real hardware GPIO/I2C in LinuxBoard is compiled in automatically (guarded by ARDULINUX_HARDWARE, which ArduLinux defines when libgpiod is detected via pkg-config); without it the build falls back to ArduLinux's simulated devices.

The following repeater is live and in service using this linux branch on a Raspberry Pi 4B with a LoRa hat: MeshCoreD LinuxRepeater (63, region BER)

• https://analyzer.letsmesh.net/nodes/repeaters?public_key=63E822CAEE5548B7CB891F002F032247C1F54B08CEC4E39EAD2450F5C06E6AE2

I'll attach screenshots from remote management as manual testing did not reveal any issues.

/cc @ggodlewski

[l5yth]

The benefit of Portduino is it "just works" (tm) with very little overhead on our end.

If we prefer to not use an external framework, we can also implement a minimal Arduino abstraction layer ourselves. I gave it a go (unreviewed yet) and it only adds ~600-800 lines of code to the Linux variant.

l5yth#3

Please let me know if you prefer it this way over the rather minimalist Portduino variant.

[ggodlewski]

The benefit of Portduino is it "just works" (tm) with very little overhead on our end.

If we prefer to not use an external framework, we can also implement a minimal Arduino abstraction layer ourselves. I gave it a go (unreviewed yet) and it only adds ~600-800 lines of code to the Linux variant.

l5yth#3

Please let me know if you prefer it this way over the rather minimalist Portduino variant.

I like it more. Portduino did not allow me to run 2 concurrent meshcore services at once (with separate config and workdir).

[liamcottle]

I haven't read through all the comments and discussions on this, but my personal preference would be to avoid depending on a Meshtastic owned project.

Portduino does look like a neat project, but I tend to avoid GPL licensed code, and we've had issues with using some of their GPL licensed code in MIT related projects in the past.

Plus, it would be good to not have to rely on an external project getting updated if we can do it in house with a small wrapper/helper class to shim out the Arduino methods as you suggested.

[l5yth]

Thanks, I appreciate the early feedback.

@ggodlewski are you still using your Pi Zero 2W? Mind giving this a test? It is upgraded to 1.14.0 now and I added your config to a ini file named .pow-sx1262 - it does read the ini on first run, so you don't need to set advert name and admin password as build flag anymore. It might need to recreate the com_prefs in the working dir.

@liamcottle Thanks for the comment. I spent some more time replacing the Portduino framework but it turns out it's not as straight-forward as I hoped it would be. As a middle ground, what do you think about hosting our own minimalist 'portduino' framework in the meshcore-dev organization (meshduino?)? Would give us a bit more control and we can iterate faster without needing to add too much code to the firmware itself.

[Littleaton]

I would be happy to help you test any of this I have many pi/nebra setups i could use. @l5yth

[l5yth]

@liamcottle this is ready for review. I removed platform native, framework portduino, and all monkey-patched meshtastic modules. Instead, I created a clean-slate platform for linux support of arduino API with only upstream dependencies (no copy-paste, no drive-by-patching).

Benefit is, that this allowed me to make meshcored on linux a proper cli daemon.

❯ meshcored --help 
meshcored linux-1.15.1-6c50a196
a meshcore daemon for linux

Usage: meshcored [OPTION...] 

  -d, --fsdir=DIR            The directory to use as the virtual filesystem
  -e, --erase                Erase virtual filesystem before use
      --usage                Give a short usage message
  -?, --help                 Give this help list
  -V, --version              Print program version

Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.

Report bugs to https://github.com/meshcore-dev/MeshCore.

@Littleaton please do. I just finished the work on this. working branch is linux - and instructions are in the linux variant README. all you need to do is double check pin mapping on your hardware. let me know.

[Littleaton]

@liamcottle this is ready for review. I removed platform native, framework portduino, and all monkey-patched meshtastic modules. Instead, I created a clean-slate platform for linux support of arduino API with only upstream dependencies (no copy-paste, no drive-by-patching).

Benefit is, that this allowed me to make meshcored on linux a proper cli daemon.

❯ meshcored --help 
meshcored linux-1.15.1-6c50a196
a meshcore daemon for linux

Usage: meshcored [OPTION...] 

  -d, --fsdir=DIR            The directory to use as the virtual filesystem
  -e, --erase                Erase virtual filesystem before use
      --usage                Give a short usage message
  -?, --help                 Give this help list
  -V, --version              Print program version

Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.

Report bugs to https://github.com/meshcore-dev/MeshCore.

@Littleaton please do. I just finished the work on this. working branch is linux - and instructions are in the linux variant README. all you need to do is double check pin mapping on your hardware. let me know.

very cool id be happy to contrib all the diff radio yaml/config files that are used, do you have this type of thing setup?

[Littleaton]

Also are you on discord so i can discuss/talk faster? :P @l5yth

[l5yth]

I don't have Discord, sorry. Feel free to suggest new configs directly in my downstream repo, wdyt?

[Littleaton]

ok can do.

[Littleaton]

OK i would suggest some sort of radio config file per radio like MT or PyMC does. so the system itself can have its own then a config.d or w/e folder with all the individual radios in that.

but ill get up what i can and go from there.