Rust: build for atmega16

Question

I would like to write a simple program and compile it for atmega16. How do I add atmega16 as a compilation target? There are little to no docs about this...

Thanks

Answer 1

The only built-in AVR target is avr-unknown-gnu-atmega328. If you are using a different AVR microcontroller, you need a custom target.

The AVR-Rust Guidebook describes how to add custom targets for different AVR microcontrollers. The process boils down to:

1. Export the JSON specification for the built-in atmega328 target, to use as a template

   rustc --print target-spec-json -Z unstable-options --target avr-unknown-gnu-atmega328 > avr-unknown-gnu-atmega16.json
   

2. Edit this JSON file. I found that to get it to compile for atmega16, I had to change the following:

   "cpu": "atmega16",
   "is-builtin": false,
   "-mmcu=atmega16"
   

   Note:

   • The CPU is specified as "atmega16" not "atmega16p" as you had attempted to use
   • I don't have any atmega16 MCU to hand so I have not been able to test the resulting binary. You may need to tweak other elements of the file.
   • You will also need to install avr-gcc, as Rust uses it to link the resulting binary. You can get that here.

3. You should then be able to build your project like this:

   cargo build -Z build-std=core --target ./avr-unknown-gnu-atmega16.json --release
   

   Note that --target is specified as the path to the JSON file. If in the same directory, prefix with ./.