Compiling for ATmega4809; "no register group defined for this port"

[timwalls]

Hiya,

First of all, thanks all for all the work on Rust/AVR, it's awesome :).

Secondly though, I'm trying to get Rust working with the Arduino Nano Every board (electrically (and cost-wise) it's perfect for my project), which uses the ATmega4809 chip...

It turns out this is quite tricky and I've been going round in a few loops, but right now I'm stuck at getting ruduino to build. avr-mcu seems to load the packfile OK, but ruduino doesn't like what it sees:

[Sasha:rust/rust-arduino-blink] timwa% cargo build
   Compiling rustc-std-workspace-core v1.99.0 (/Users/timwa/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/src/rust/library/rustc-std-workspace-core)
   Compiling ruduino v0.2.6
   Compiling compiler_builtins v0.1.35
error: failed to run custom build command for `ruduino v0.2.6`

Caused by:
  process didn't exit successfully: `/Volumes/Development/Arduino/rust/rust-arduino-blink/target/debug/build/ruduino-1f365ea4228ae98b/build-script-build` (exit code: 101)
  --- stdout
  loading pack '/Users/timwa/.cargo/registry/src/github.com-1ecc6299db9ec823/avr-mcu-0.3.4/packs/atmega/ATmega4809.atdf'

  --- stderr
  [warning]: cannot find target JSON file 'atmega4809.json' - due to limitations it needs to be in the crate root - is it?
  [warning]: assuming a target CPU name of 'atmega4809' from the file name of the target spec JSON file
  thread 'main' panicked at 'no register group defined for this port', /Users/timwa/.cargo/registry/src/github.com-1ecc6299db9ec823/ruduino-0.2.6/core_generator/gen.rs:65:22
  stack backtrace:
     0:        0x1044d20a4 - std::backtrace_rs::backtrace::libunwind::trace::hb4ff9014ec5817b3
                                 at /rustc/7bade6ef730cff83f3591479a98916920f66decd/library/std/src/../../backtrace/src/backtrace/libunwind.rs:100:5
     1:        0x1044d20a4 - std::backtrace_rs::backtrace::trace_unsynchronized::h0d03cf0f7c5d8d01
                                 at /rustc/7bade6ef730cff83f3591479a98916920f66decd/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
     2:        0x1044d20a4 - std::sys_common::backtrace::_print_fmt::h5b2bf2921eea85ae

Before I start digging too deep attempting to work out the problem myself, does this seem to have an obvious cause to anyone (and thus an obvious solution? :-D.)

Thanks in advance, Tim

[harpekar]

I'm getting a similar error trying to compile for the atmega32u4, did you figure out what's going on?

[timwalls]

Hey, hi.

To be honest, I gave up with ruduino - I was making no progress. I switched to @rahix's Rahix/avr-hal, which seems to be under more active development, at least for devices other than the standard '189.

In the case of the 4809, smarter people than I are already working on it, but even without that being ready yet I found it much easier to adapt the underlying Rahix/avr-device package to get something working.

If anyone comes to this wondering about the ATmega4809/Nano Every in particular - you can find a fork of avr-device/avr-hal which at least gives you basic working pin access at timwalls/avr-device:ATmega4809 and timwalls/avr-hal:arduino-nano-every respectively. I've not done anything about getting things like UARTs working yet because, as I say, other smarter people are working on that and eventually I expect to go back to the mainline once 4809 support is rolled in. But even if that doesn't happen, I'm confident this is a much easier place to start getting those things to work than ruduino.

For your specific needs @harpekar, it looks like avr-device/avr-hal already has ATmega32u4 support in there - so I'd definitely suggest taking a look there :).