How to start new project with atmega-hal with bare MCU (no arduino)

[T0maas]

How to start new project and what do I need to write to Cargo.toml? I've just downloaded cargo on my linux distro so I have fresh instalation of rust.
I want to use atmega-hal (not arduino-hal, because I need better control over MCU: timers, prescalers, PWM, ADC, ...), and I have those questions:

• Where to specify target MCU (for example atmega328p or attiny85 or atmega48 or atmega2560) ?
• Where to specify F_CPU (I want to use 8MHz internal oscilator)?
• I did not find atmega-hal or avr-hal in cargo search how to add them to Cargo.toml?
• Is running cargo build enough to produce avr compatible binary or do I need to specify some additional arguments?
• Do I need to manually download some rust toolchains?
• If I have avrdude (and I am used to work with it) do I need ravedude or is it optional?
• Is there some getting started documentation which describes above questions?

I've read some examples, but they are using relative paths like this:

[dependencies.atmega-hal]
path = "../../mcu/atmega-hal/"
features = ["atmega2560"]

And I cant use this in my project (where Cargo.toml is in project root directory). Do I need to download this repo somewhere and point path to this directory inside my project?

I have this setup:

Default host: x86_64-unknown-linux-gnu
rustup home:  /home/tom/.rustup

stable-x86_64-unknown-linux-gnu (default)
rustc 1.83.0 (90b35a623 2024-11-26)

I've found somewhere that I need to run rustup target add avr-atmega328p but it ended with error:

error: toolchain 'stable-x86_64-unknown-linux-gnu' does not support target 'avr-atmega328p'

I also tried this:
cargo doc --features atmega328p --open

but it wrote:

error: the package 'atmega328example' does not contain this feature: atmega328p

where atmega328example is name of my project directory. It's fresh directory just created using cargo init.

I'tried cargo generate --git https://github.com/Rahix/avr-hal-template.git but it has no option for bare atmega328p (only arduino UNO was closest) and it uses arduino-hal instead of atmega-hal.

[stappersg]

On Sun, Dec 29, 2024 at 06:19:07AM -0800, T0maas wrote: I'tried `cargo generate --git https://github.com/Rahix/avr-hal-template.git` but it has no option for bare atmega328p (only arduino UNO was closest) and it uses arduino-hal instead of atmega-hal.

``` cargo generate --git https://github.com/Rahix/avr-hal-template.git cd projectname cargo build ``` From that "known good" start making changes. Use `cargo build` to verify it still build. And at some point deploy to the actual hardware. Groeten Geert Stappers -- Silence is hard to parse

[T0maas]

From that "known good" start making changes.

But how? Which changes? What do I need to write to Cargo.toml to make correct configuration for baremetal atmega328p with 8MHz clock?

[Rahix]

The clock rate is defined like this, for example:

avr-hal/examples/atmega2560/src/bin/atmega2560-i2cdetect.rs

Lines 7 to 8 in 4bf713c

	// Define core clock in the root crate
	type CoreClock = atmega_hal::clock::MHz16;

[stappersg]

On Mon, Dec 30, 2024 at 12:16:46PM -0800, T0maas wrote: > From that "known good" start making changes. But how?

Yes, so true.

Which changes?

Your changes to a known good, your changes that bring you closer to your goal.

What do I need to write to Cargo.toml to make correct configuration for baremetal atmega328p with 8MHz clock?

https://github.com/Rahix/avr-hal/discussions?discussions_q=clock did yield #318 which has title "Target microcontroller directly instead of an arduino board" Please advice how to improve our documentation. (Karma bonus points for merge requests.) And please accept my apology. I'm sorry that I did not ignore the original posting. http://www.catb.org/~esr/faqs/smart-questions.html says I should have ignored it. Groeten Geert Stappers -- Silence is hard to parse

[T0maas]

Is there some complex documentation? I found only this: https://rahix.github.io/avr-hal/atmega_hal/index.html. I tried to run cargo doc --features atmega328p --open inside avr-hal-template and i've got error:

error: none of the selected packages contains these features: atmega328p

[Rahix]

You need to run this command from the atmega-hal or attiny-hal directories.

[Rahix]

Unfortunately the bare-metal workflow isn't documented well at the moment.

Check the Quickstart Guide and especially the avr-hal-template. I suggest setting up for an Arduino board similar to your target MCU.

Then check the "bare AVR" examples crate here: https://github.com/Rahix/avr-hal/tree/main/examples/atmega2560

You will have to adapt the template you just generated from avr-hal-template according to the stuff you find in that example directory. Most importantly, switch from depending on arduino-hal to depending on atmega-hal (or attiny-hal), using the same git dependency.