Access USB devices from Ruby
LIBUSB is a Ruby binding that gives Ruby programmers access to arbitrary USB devices.
- libusb is a library that gives full access to devices connected via the USB bus. No special kernel driver is thus necessary for accessing USB devices.
- This Ruby binding supports the API version 1.0 of libusb. Note that the old "legacy" version 0.1.x of libusb uses a completely different API that is covered by the ruby extension ruby-usb .
LIBUSB for Ruby is covered by the GNU Lesser General Public License version 3.
- Access to descriptors of devices, configurations, interfaces, settings and endpoints
- Synchronous and asynchronous communication for bulk, control, interrupt and isochronous transfers
- Support for USB-3.0 descriptors and bulk streams
- Compatibility layer for ruby-usb (API based on libusb-0.1). See for description.
require "libusb" usb = LIBUSB::Context.new device = usb.devices(idVendor: 0x04b4, idProduct: 0x8613).first device.open_interface(0) do |handle| handle.control_transfer(bmRequestType: 0x40, bRequest: 0xa0, wValue: 0xe600, wIndex: 0x0000, dataOut: 1.chr) end
is used to get all or only particular devices. After the the resulting can be used to communicate with the connected USB device by , , or by using the classes.
Acan also be used to retrieve information about it, by using the device descriptor attributes. A could have several configurations. You can then decide of which configuration to enable. You can only enable one configuration at a time.
Eachhas one or more interfaces. These can be seen as functional group performing a single feature of the device.
Eachhas at least one . The first setting is always default. An alternate setting can be used independent on each interface.
Eachspecifies it's own set of communication endpoints. Each specifies the type of transfer, direction, polling interval and maximum packet size.
See the documentation for a full API description.
- Linux, MacOS or Windows system with Ruby MRI 1.9/2.x, JRuby or recent version of Rubinius
Optionally: libusb C-library version 1.0.8 or any newer version. The system libusb library can be installed like so:
- Debian or Ubuntu:
$ sudo apt-get install libusb-1.0-0
- MacOS: install with homebrew:
$ brew install libusb
$ port install libusb
- Windows: libusb.gem already comes with a precompiled
libusb.dll, but you need to install a device driver (see below)
$ gem install libusb
gem install the system is checked for a usable libusb library installation.
If none could be found, a bundled libusb version is built and used, instead.
Latest code can be used in this way:
$ git clone git://github.com/larskanis/libusb.git $ bundle $ rake install_gem
In order to implement a driver for a USB device, it's essential to have a look at the packets that are send to and received back from the USB device. Wireshark has builtin capabilities to sniff USB traffic. On Linux you possibly need to load the usbmon kernel module before start:
sudo modprobe usbmon
On Windows it's possible to sniff USB, if the USB kernel driver was installed by the Wireshark setup.
Device hotplug support
Support for device hotplugging can be used, if
This requires libusb-1.0.16 or newer on Linux or MacOS. Windows support is still on the way.
A hotplug event handler can be registered with. You then need to call in order to receive any events. This can be done as blocking calls (possibly in it's own thread) or by using to detect any events to handle.
Usage on Windows
In contrast to Linux, any access to an USB device by LIBUSB on Windows requires a proper driver installed in the system. Fortunately creating such a driver is quite easy with Zadig. Select the interesting USB device, choose WinUSB driver and press "Install Driver". That's it. You may take the generated output directory with it's INI-file and use it for driver installations on other 32 or 64 bit Windows systems.
Cross compiling for Windows
Libusb-gem can be cross built for Windows and Linux operating systems, using the rake-compiler-dock . Just run:
$ rake gem:native
If everything works, there are several platform specific gem files (like
libusb-VERSION-x64-mingw32.gem) in the pkg
Libusb for Ruby comes with an experimental integration to EventMachine. That API is currently proof of concept - see . If you're experienced with EventMachine, please leave a comment.
- Project's home page: http://github.com/larskanis/libusb
- API documentation: http://rubydoc.info/gems/libusb/frames
- Mailinglist: http://rubyforge.org/mailman/listinfo/libusb-hackers
- Overall introduction to USB: http://www.usbmadesimple.co.uk
- stabilize EventMachine interface