Quickly set up a probe-rs + defmt + flip-link embedded project running on the RTIC scheduler

Based on https://github.com/knurling-rs/app-template

$ cargo install flip-link

$ cargo install probe-rs --features cli

$ git clone https://github.com/rtic-rs/app-template test-app

If you look into your new test-app folder, you'll find that there are a few TODOs in the files marking the properties you need to set. The todo's are formatted as TODO(n), where n is the number of the step in which the TODO is explained.

Let's walk through them together now.

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.

# .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"

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

 # .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.

$ rustup +nightly target add thumbv7em-none-eabihf

In Cargo.toml, activate the correct rtic backend for your target by replacing $RTIC_BACKEND with one of thumbv6-backend, thumbv7-backend, thumbv8base-backend, or thumbv8main-backend, depending on the target you are compiling for.

# Cargo.toml
-rtic = { version = "2.0.0", features = [ "$RTIC_BACKEND" ] }
+rtic = { version = "2.0.0", features = [ "thumbv7-backend" ] }

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.

# Cargo.toml
 [dependencies]
-some-hal = "1.2.3"
+nrf52840-hal = "0.16.0"

⚠️ 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.

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

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

In src/bin/minimal.rs, edit the rtic::app macro into a valid form.

# my-app/src/bin/minimal.rs
\#[rtic::app(
-    // TODO: Replace `some_hal::pac` with the path to the PAC
-    device = some_hal::pac,
-    // TODO: Replace the `FreeInterrupt1, ...` with free interrupt vectors if software tasks are used
-    // You can usually find the names of the interrupt vectors in the some_hal::pac::interrupt enum.
-    dispatchers = [FreeInterrupt1, ...]
+    device = nrf52840_hal::pac,
+    dispatchers = [SWI0_EGU0]
)]

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.

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/minimal.rs:

$ # `rb` is an alias for `run --bin`
$ DEFMT_LOG=trace cargo rb minimal
    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_BRTT_BUFFER_SIZE environment variable. The default value is 1024 bytes, and powers of two should be used for optimal performance:

$ DEFMT_BRTT_BUFFER_SIZE=64 cargo rb minimal

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.

Licensed under either of

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

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

at your option.

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.