Expand description
A new library for cross-platform low-level access to USB devices.
nusb is comparable to the C library libusb and its Rust bindings rusb,
but written in pure Rust. It’s built on and exposes async APIs by default,
but can be made blocking using futures_lite::future::block_on
or similar.
Use nusb to write user-space drivers in Rust for non-standard USB devices
or those without kernel support. For devices implementing a standard USB
class such as Mass Storage, CDC (Serial), HID, Audio, or Video, this is
probably not the library you’re looking for – use something built on the
existing kernel driver instead. (On some platforms you could detach or
replace the kernel driver and program the device from user-space using this
library, but you’d have to re-implement the class functionality yourself.)
§USB and usage overview
When a USB device connects, the OS queries the device descriptor containing
basic device information such as the vendor and product ID (VID / PID) and
string descriptors like the manufacturer, product, and serial number
strings. list_devices returns an iterator listing connected USB devices,
which can be filtered by these fields to identify and select the desired
device.
Call device_info.open() to open a selected device.
Additional information about the device can be queried with
device.active_configuration().
USB devices consist of one or more interfaces exposing a group of
functionality. A device with multiple interfaces is known as a composite
device. To open an interface, call Device::claim_interface. Only one
program (or kernel driver) may claim an interface at a time.
Use the resulting Interface to transfer data on the device’s control,
bulk or interrupt endpoints. Transfers are async by default, and can be
awaited as individual Futures, or use a
Queue to manage streams of data.
For more details on how USB works, USB in a Nutshell is a good overview.
§Logging
nusb uses the log crate to log debug and error
information.
When submitting a bug report, please include the logs: use a
log backend like env_logger and configure
it to enable log output for this crate (for env_logger set environment
variable RUST_LOG=nusb=debug.)
§Platform support
§Linux
nusb is built on the kernel’s usbfs API.
A user must have write access on the /dev/bus/usb/XXX/YYY nodes to
successfully open a device. Use udev rules to configure these permissions.
For a single-user system used for development, it may be desirable to give
your user account access to all USB devices by placing the following in
/etc/udev/rules.d/70-plugdev-usb.rules:
SUBSYSTEM=="usb", MODE="0660", GROUP="plugdev"
This grants access on all USB devices to the plugdev group, which your
user may be a member of by default on Debian/Ubuntu-based distros. If you
are developing an app for others to install, you should scope the
permissions more narrowly using the ATTRS{idVendor}=="ZZZZ", ATTRS{idProduct}=="ZZZZ" filters to only apply to your device.
§Windows
nusb uses WinUSB on Windows.
On Windows, devices are associated with a particular driver, which persists across connections and reboots. Composite devices appear as multiple devices in the Windows device model, and each interface can be associated with a separate driver.
To use nusb, your device or interface must be associated with the WinUSB
driver. If you control the device firmware, the recommended way is to use a
WCID descriptor to tell Windows to install the WinUSB driver automatically
when the device is first connected. Alternatively Zadig (GUI) or libwdi
(CLI / C library) can be used to manually install the WinUSB driver for a
device.
§macOS
nusb uses IOKit on macOS.
Users have access to USB devices by default, with no permission configuration needed. Devices with a kernel driver are not accessible.
Modules§
- Utilities for parsing USB descriptors.
- Transfer-related types.
Structs§
- An opened USB device.
- Information about a device that can be obtained without opening it.
- An opened interface of a USB device.
- Summary information about a device’s interface, available before opening a device.
Enums§
- USB connection speed
Functions§
- Get an iterator listing the connected devices.
Type Aliases§
- OS error returned from operations other than transfers.