embassy/docs/pages/project_structure.adoc

= Project Structure

There are many ways to configure embassy and its components for your exact application. The link:https://github.com/embassy-rs/embassy/tree/main/examples[examples] directory for each chipset demonstrates how your project structure should look. Let's break it down:

The toplevel file structure of your project should look like this:
[source,plain]
----
{} = Maybe

my-project
|- .cargo
|  |- config.toml
|- src
|  |- main.rs
|- build.rs
|- Cargo.toml
|- {memory.x}
|- rust-toolchain.toml
----

[discrete]
== .cargo/config.toml

This directory/file describes what platform you're on, and configures link:https://github.com/probe-rs/probe-rs[probe-rs] to deploy to your device.

Here is a minimal example:

[source,toml]
----
[target.thumbv6m-none-eabi] # <-change for your platform
runner = 'probe-rs run --chip STM32F031K6Tx' # <- change for your chip

[build]
target = "thumbv6m-none-eabi" # <-change for your platform

[env]
DEFMT_LOG = "trace" # <- can change to info, warn, or error
----

[discrete]
== build.rs

This is the build script for your project. It links defmt (what is link:https://defmt.ferrous-systems.com[defmt]?) and the `memory.x` file if needed. This file is pretty specific for each chipset, just copy and paste from the corresponding link:https://github.com/embassy-rs/embassy/tree/main/examples[example].

[discrete]
== Cargo.toml

This is your manifest file, where you can configure all of the embassy components to use the features you need.

[discrete]
=== Features

[discrete]
==== Time
- tick-hz-x: Configures the tick rate of `embassy-time`. Higher tick rate means higher precision, and higher CPU wakes.
- defmt-timestamp-uptime: defmt log entries will display the uptime in seconds.

...more to come

[discrete]
== memory.x

This file outlines the flash/ram usage of your program. It is especially useful when using link:https://github.com/embassy-rs/nrf-softdevice[nrf-softdevice] on an nRF5x.

Here is an example for using S140 with an nRF52840:

[source,x]
----
MEMORY
{
  /* NOTE 1 K = 1 KiBi = 1024 bytes */
  /* These values correspond to the NRF52840 with Softdevices S140 7.0.1 */
  FLASH : ORIGIN = 0x00027000, LENGTH = 868K
  RAM : ORIGIN = 0x20020000, LENGTH = 128K
}
----

[discrete]
== rust-toolchain.toml

This file configures the rust version and configuration to use.

A minimal example:

[source,toml]
----
[toolchain]
channel = "nightly-2023-08-19" # <- as of writing, this is the exact rust version embassy uses
components = [ "rust-src", "rustfmt" ] # <- optionally add "llvm-tools-preview" for some extra features like "cargo size"
targets = [
    "thumbv6m-none-eabi" # <-change for your platform
]
----