mirror of
https://github.com/embassy-rs/embassy.git
synced 2024-11-21 22:32:29 +00:00
51 lines
2.0 KiB
Markdown
51 lines
2.0 KiB
Markdown
# embassy-usb
|
|
|
|
Async USB device stack for embedded devices in Rust.
|
|
|
|
## Features
|
|
|
|
- Native async.
|
|
- Fully lock-free: endpoints are separate objects that can be used independently without needing a central mutex. If the driver supports it, they can even be used from different priority levels.
|
|
- Suspend/resume, remote wakeup.
|
|
- USB composite devices.
|
|
- Ergonomic descriptor builder.
|
|
- Ready-to-use implementations for a few USB classes (note you can still implement any class yourself outside the crate).
|
|
- Serial ports (CDC ACM)
|
|
- Ethernet (CDC NCM)
|
|
- Human Interface Devices (HID)
|
|
- MIDI
|
|
|
|
## Adding support for new hardware
|
|
|
|
To add `embassy-usb` support for new hardware (i.e. a new MCU chip), you have to write a driver that implements
|
|
the [`embassy-usb-driver`](https://crates.io/crates/embassy-usb-driver) traits.
|
|
|
|
Driver crates should depend only on `embassy-usb-driver`, not on the main `embassy-usb` crate.
|
|
This allows existing drivers to continue working for newer `embassy-usb` major versions, without needing an update, if the driver
|
|
trait has not had breaking changes.
|
|
|
|
## Configuration
|
|
|
|
`embassy-usb` has some configuration settings that are set at compile time, affecting sizes
|
|
and counts of buffers.
|
|
|
|
They can be set in two ways:
|
|
|
|
- Via Cargo features: enable a feature like `<name>-<value>`. `name` must be in lowercase and
|
|
use dashes instead of underscores. For example. `max-interface-count-3`. Only a selection of values
|
|
is available, check `Cargo.toml` for the list.
|
|
- Via environment variables at build time: set the variable named `EMBASSY_USB_<value>`. For example
|
|
`EMBASSY_USB_MAX_INTERFACE_COUNT=3 cargo build`. You can also set them in the `[env]` section of `.cargo/config.toml`.
|
|
Any value can be set, unlike with Cargo features.
|
|
|
|
Environment variables take precedence over Cargo features. If two Cargo features are enabled for the same setting
|
|
with different values, compilation fails.
|
|
|
|
### `MAX_INTERFACE_COUNT`
|
|
|
|
Max amount of interfaces that can be created in one device. Default: 4.
|
|
|
|
## Interoperability
|
|
|
|
This crate can run on any executor.
|