The usb
package is a cross platform, fully self-contained library for accessing and communicating with USB devices either via HID or low level interrupts. The goal of the library was to create a simple way to find-, attach to- and read/write form USB devices.
There are multiple already existing USB libraries:
- The original
gousb
package created by @kylelemons and nowadays maintained by @google is a CGO wrapper aroundlibusb
. It is the most advanced USB library for Go out there.- Unfortunately,
gousb
requires thelibusb
C library to be installed both during build as well as during runtime on the host operating system. This breaks binary portability and also adds unnecessary hurdles on Windows. - Furthermore, whilst HID devices are supported by
libusb
, the OS on Macos and Windows explicitly takes over these devices, so only native system calls can be used on recent versions (i.e. you cannot uselibusb
for HID).
- Unfortunately,
- There is a fork of
gousb
created by @karalabe that statically linkedlibusb
during build, but with the lack of HID access, that work was abandoned. - For HID-only devices, a previous self-contained package was created at
github.com/karalabe/hid
, which worked well for hardware wallet uses cases ingo-ethereum
. It's a simple package that does it's thing well.- Unfortunately,
hid
is not capable of talking to generic USB devices. When multiple different devices are needed, eventually some will not support the HID spec (e.g. WebUSB). Pulling in bothhid
andgousb
will break down due to both depending internally on different versions oflibusb
on Linux.
- Unfortunately,
This usb
package is a proper integration of hidapi
and libusb
so that communication with HID devices is done via system calls, whereas communication with lower level USB devices is done via interrupts. All this detail is hidden away behind a tiny interface.
The package supports Linux, macOS, Windows and FreeBSD. Exclude constraints are also specified for Android and iOS to allow smoother vendoring into cross platform projects.
Using go get
, the embedded C library is compiled into the binary format of your host OS. Cross compiling to a different platform or architecture entails disabling CGO by default in Go, causing device enumeration hid.Enumerate()
to yield no results.
To cross compile a functional version of this library, you'll need to enable CGO during cross compilation via CGO_ENABLED=1
and you'll need to install and set a cross compilation enabled C toolkit via CC=your-cross-gcc
.
Although the usb
package is an implementation from scratch, HID support was heavily inspired by the existing go.hid
library, which seems abandoned since 2015; is incompatible with Go 1.6+; and has various external dependencies.
Wide character support in the HID support is done via the gowchar
library, unmaintained since 2013; non buildable with a modern Go release and failing go vet
checks. As such, gowchar
was also vendored in inline.
Error handling for the libusb
integration originates from the gousb
library.
This USB library is licensed under the GNU Lesser General Public License v3.0 (dictated by libusb).
If you are only interested in Human Interface devices, a less restrictive package can be found at github.com/karalabe/hid