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