As an example, let’s create a new embassy project from scratch for a STM32G474. The same instructions are applicable for any supported chip with some minor changes.
Looking in link:https://github.com/embassy-rs/embassy/tree/main/examples[the Embassy examples], we can see there’s a `stm32g4` folder. Find `src/blinky.rs` and copy its contents into our `src/main.rs`.
Currently, we’d need to provide cargo with a target triple every time we run `cargo build` or `cargo run`. Let’s spare ourselves that work by copying `.cargo/config.toml` from `examples/stm32g4` into our project.
In addition to a target triple, `.cargo/config.toml` contains a `runner` key which allows us to conveniently run our project on hardware with `cargo run` via probe-rs. In order for this to work, we need to provide the correct chip ID. We can do this by checking `probe-rs chip list`:
[source,bash]
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$ probe-rs chip list | grep -i stm32g474re
STM32G474RETx
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and copying `STM32G474RETx` into `.cargo/config.toml` as so:
Now that cargo knows what target to compile for (and probe-rs knows what chip to run it on), we’re ready to add some dependencies.
Looking in `examples/stm32g4/Cargo.toml`, we can see that the examples require a number of embassy crates. For blinky, we’ll only need three of them: `embassy-stm32`, `embassy-executor` and `embassy-time`.
Prior, embassy needed to be installed straight from the git repository. Installing from git is still useful, if you want to checkout a specic revision of an embassy crate which is not yet published.
* Copy the required `embassy-*` lines from the example `Cargo.toml`
* Make any necessary changes to `features`, e.g. requiring the `stm32g474re` feature of `embassy-stm32`
* Remove the `path = ""` keys in the `embassy-*` entries
* Create a `[patch.crates-io]` section, with entries for each embassy crate we need. These should all contain identical values: a link to the git repository, and a reference to the commit we’re checking out. Assuming you want the latest commit, you can find it by running `git ls-remote https://github.com/embassy-rs/embassy.git HEAD`
NOTE: When using this method, it’s necessary that the `version` keys in `[dependencies]` match up with the versions defined in each crate’s `Cargo.toml` in the specificed `rev` under `[patch.crates.io]`. This means that when updating, you have to a pick a new revision, change everything in `[patch.crates.io]` to match it, and then correct any versions under `[dependencies]` which have changed.
There are a few other dependencies we need to build the project, but fortunately they’re much simpler to install. Copy their lines from the example `Cargo.toml` to the the `[dependencies]` section in the new `Cargo.toml`:
[source,toml]
----
defmt = "0.3.5"
defmt-rtt = "0.4.0"
cortex-m = {version = "0.7.7", features = ["critical-section-single-core"]}
cortex-m-rt = "0.7.3"
panic-probe = "0.3.1"
----
These are the bare minimum dependencies required to run `blinky.rs`, but it’s worth taking a look at the other dependencies specified in the example `Cargo.toml`, and noting what features are required for use with embassy – for example `futures = { version = "0.3.17", default-features = false, features = ["async-await"] }`.
Finally, copy the `[profile.release]` section from the example `Cargo.toml` into ours.
Before we can build our project, we need to add an additional file to tell cargo to use the nightly toolchain. Copy the `rust-toolchain.toml` from the embassy repo to ours, and trim the list of targets down to only the target triple relevent for our project — in this case, `thumbv7em-none-eabi`:
