# `app-template`

> Quickly set up a [`probe-rs`] + [`defmt`] + [`flip-link`] embedded project

[`probe-rs`]: https://crates.io/crates/probe-rs
[`defmt`]: https://github.com/knurling-rs/defmt
[`flip-link`]: https://github.com/knurling-rs/flip-link

## Dependencies

#### 1. `flip-link`:

```console
$ cargo install flip-link
```

#### 2. `probe-rs`:

``` console
$ # make sure to install v0.2.0 or later
$ cargo install probe-rs --features cli
```

#### 3. [`cargo-generate`]:

``` console
$ cargo install cargo-generate
```

[`cargo-generate`]: https://crates.io/crates/cargo-generate

> *Note:* You can also just clone this repository instead of using `cargo-generate`, but this involves additional manual adjustments.

## Setup

#### 1. Initialize the project template

``` console
$ cargo generate \
    --git https://github.com/knurling-rs/app-template \
    --branch main \
    --name my-app
```

If you look into your new `my-app` folder, you'll find that there are a few `TODO`s in the files marking the properties you need to set.

Let's walk through them together now.

#### 2. Set `probe-rs` chip

Pick a chip from ` probe-rs chip list` and enter it into `.cargo/config.toml`.

If, for example, you have a nRF52840 Development Kit from one of [our workshops], replace `{{chip}}` with `nRF52840_xxAA`.

[our workshops]: https://github.com/ferrous-systems/embedded-trainings-2020

``` diff
 # .cargo/config.toml
 [target.'cfg(all(target_arch = "arm", target_os = "none"))']
-runner = "probe-rs run --chip {{chip}}"
+runner = "probe-rs run --chip nRF52840_xxAA"
```

#### 2.1 Pass custom log format

You need to use an array of strings instead of a single string for the `runner` if you use a custom log format.

```toml
runner = ["probe-rs", "run", "--chip", "$CHIP", "--log-format", "{L} {s}"]
```

#### 3. Adjust the compilation target

In `.cargo/config.toml`, pick the right compilation target for your board.

``` diff
 # .cargo/config.toml
 [build]
-target = "thumbv6m-none-eabi"    # Cortex-M0 and Cortex-M0+
-# target = "thumbv7m-none-eabi"    # Cortex-M3
-# target = "thumbv7em-none-eabi"   # Cortex-M4 and Cortex-M7 (no FPU)
-# target = "thumbv7em-none-eabihf" # Cortex-M4F and Cortex-M7F (with FPU)
+target = "thumbv7em-none-eabihf" # Cortex-M4F (with FPU)
```

Add the target with `rustup`.

``` console
$ rustup target add thumbv7em-none-eabihf
```

#### 4. Add a HAL as a dependency

In `Cargo.toml`, list the Hardware Abstraction Layer (HAL) for your board as a dependency.

For the nRF52840 you'll want to use the [`nrf52840-hal`].

[`nrf52840-hal`]: https://crates.io/crates/nrf52840-hal

``` diff
 # Cargo.toml
 [dependencies]
-# some-hal = "1.2.3"
+nrf52840-hal = "0.14.0"
```

⚠️ Note for RP2040 users ⚠️

You will need to not just specify the `rp-hal` HAL, but a BSP (board support crate) which includes a second stage bootloader. Please find a list of available BSPs [here](https://github.com/rp-rs/rp-hal-boards#packages).

#### 5. Import your HAL

Now that you have selected a HAL, fix the HAL import in `src/lib.rs`

``` diff
 // my-app/src/lib.rs
-// use some_hal as _; // memory layout
+use nrf52840_hal as _; // memory layout
```

#### (6. Get a linker script)

Some HAL crates require that you manually copy over a file called `memory.x` from the HAL to the root of your project. For nrf52840-hal, this is done automatically so no action is needed. For other HAL crates, you can get it from your local Cargo folder, the default location is under:

```
~/.cargo/registry/src/
```

Not all HALs provide a `memory.x` file, you may need to write it yourself. Check the documentation for the HAL you are using.


#### 7. Run!

You are now all set to `cargo-run` your first `defmt`-powered application!
There are some examples in the `src/bin` directory.

Start by `cargo run`-ning `my-app/src/bin/hello.rs`:

``` console
$ # `rb` is an alias for `run --bin`
$ cargo rb hello
    Finished dev [optimized + debuginfo] target(s) in 0.03s
flashing program ..
DONE
resetting device
0.000000 INFO Hello, world!
(..)

$ echo $?
0
```

If you're running out of memory (`flip-link` bails with an overflow error), you can decrease the size of the device memory buffer by setting the `DEFMT_RTT_BUFFER_SIZE` environment variable. The default value is 1024 bytes, and powers of two should be used for optimal performance:

``` console
$ DEFMT_RTT_BUFFER_SIZE=64 cargo rb hello
```

#### (8. Set `rust-analyzer.linkedProjects`)

If you are using [rust-analyzer] with VS Code for IDE-like features you can add following configuration to your `.vscode/settings.json` to make it work transparently across workspaces. Find the details of this option in the [RA docs].

```json
{
    "rust-analyzer.linkedProjects": [
        "Cargo.toml",
        "firmware/Cargo.toml",
    ]
}
```

[RA docs]: https://rust-analyzer.github.io/manual.html#configuration
[rust-analyzer]: https://rust-analyzer.github.io/

## Running tests

The template comes configured for running unit tests and integration tests on the target.

Unit tests reside in the library crate and can test private API; the initial set of unit tests are in `src/lib.rs`.
`cargo test --lib` will run those unit tests.

``` console
$ cargo test --lib
(1/1) running `it_works`...
└─ app::unit_tests::__defmt_test_entry @ src/lib.rs:33
all tests passed!
└─ app::unit_tests::__defmt_test_entry @ src/lib.rs:28
```

Integration tests reside in the `tests` directory; the initial set of integration tests are in `tests/integration.rs`.
`cargo test --test integration` will run those integration tests.
Note that the argument of the `--test` flag must match the name of the test file in the `tests` directory.

``` console
$ cargo test --test integration
(1/1) running `it_works`...
└─ integration::tests::__defmt_test_entry @ tests/integration.rs:13
all tests passed!
└─ integration::tests::__defmt_test_entry @ tests/integration.rs:8
```

Note that to add a new test file to the `tests` directory you also need to add a new `[[test]]` section to `Cargo.toml`.

## Support

`app-template` is part of the [Knurling] project, [Ferrous Systems]' effort at
improving tooling used to develop for embedded systems.

If you think that our work is useful, consider sponsoring it via [GitHub
Sponsors].

## License

Licensed under either of

- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
  http://www.apache.org/licenses/LICENSE-2.0)

- MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)

at your option.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
licensed as above, without any additional terms or conditions.

[Knurling]: https://knurling.ferrous-systems.com
[Ferrous Systems]: https://ferrous-systems.com/
[GitHub Sponsors]: https://github.com/sponsors/knurling-rs