usb

Library to access USB devices

npm install usb
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USB Library for Node.JS

POSIX: Build Status     Windows: Build status

Node.JS library for communicating with USB devices in JavaScript / CoffeeScript.

This is a refactoring / rewrite of Christopher Klein's node-usb. The API is not compatible (hopefully you find it an improvement).

It's based entirely on libusb's asynchronous API for better efficiency, and provides a stream API for continuously streaming data or events.

Tested with Node 0.10/Fedora and Node 0.10/WinXP.

Installation

Libusb is required. Older versions of libusb segfault when using bulk or interrupt endpoints. Use libusb or libusbx 1.0.9 or greater.

Ubuntu/Debian: sudo apt-get install build-essential pkg-config libusb-1.0-0-dev
Fedora: sudo yum install libusbx-devel

OSX: brew install libusb pkg-config

Windows: Download a Windows Binary package from http://libusbx.org/ and extract it at C:\Program Files\libusb. Use Zadig to install the WinUSB driver for your USB device. Otherwise you will get a LIBUSB_ERROR_NOT_SUPPORTED when attempting to open devices.

Then, just run

npm install usb

to install from npm. See the bottom of this page for instructions for building from a git checkout.

API

var usb = require('usb')

usb

Top-level object.

usb.getDeviceList()

Return a list of Device objects for the USB devices attached to the system.

usb.findByIds(vid, pid)

Convenience method to get the first device with the specified VID and PID, or undefined if no such device is present.

usb.LIBUSB_*

Constant properties from libusb

usb.setDebugLevel(level : int)

Set the libusb debug level (between 0 and 4)

Device

Represents a USB device.

.busNumber

Integer USB device number

.deviceAddress

Integer USB device address

.deviceDescriptor

Object with properties for the fields of the device descriptor:

  • bLength
  • bDescriptorType
  • bcdUSB
  • bDeviceClass
  • bDeviceSubClass
  • bDeviceProtocol
  • bMaxPacketSize0
  • idVendor
  • idProduct
  • bcdDevice
  • iManufacturer
  • iProduct
  • iSerialNumber
  • bNumConfigurations

.configDescriptor

Object with properties for the fields of the configuration descriptor:

  • bLength
  • bDescriptorType
  • wTotalLength
  • bNumInterfaces
  • bConfigurationValue
  • iConfiguration
  • bmAttributes
  • bMaxPower
  • extra (Buffer containing any extra data or additional descriptors)

.open()

Open the device. All methods below require the device to be open before use.

.close()

Close the device.

.controlTransfer(bmRequestType, bRequest, wValue, wIndex, data_or_length, callback(error, data))

Perform a control transfer with libusb_control_transfer.

Parameter data_or_length can be a integer length for an IN transfer, or a Buffer for an out transfer. The type must match the direction specified in the MSB of bmRequestType.

The data parameter of the callback is always undefined for OUT transfers, or will be passed a Buffer for IN transfers.

.getStringDescriptor(index, callback(error, data))

Perform a control transfer to retrieve a string descriptor

.interface(interface)

Return the interface with the specified interface number.

.interfaces

List of Interface objects for the interfaces of the default configuration of the device.

.timeout

Timeout in milliseconds to use for controlTransfer and endpoint transfers.

.reset(callback(error))

Performs a reset of the device. Callback is called when complete.

Interface

.endpoint(address)

Return the InEndpoint or OutEndpoint with the specified address.

.endpoints

List of endpoints on this interface: InEndpoint and OutEndpoint objects.

.interface

Integer interface number.

.altSetting

Integer alternate setting number.

.setAltSetting(altSetting, callback(error))

Sets the alternate setting. It updates the interface.endpoints array to reflect the endpoints found in the alternate setting.

.claim()

Claims the interface. This method must be called before using any endpoints of this interface.

.release(callback(error))

Releases the interface and resets the alternate setting. Calls callback when complete.

.isKernelDriverActive()

Returns false if a kernel driver is not active; true if active.

.detachKernelDriver()

Detaches the kernel driver from the interface.

.attachKernelDriver()

Re-attaches the kernel driver for the interface.

.descriptor

Object with fields from the interface descriptor -- see libusb documentation or USB spec.

  • bLength
  • bDescriptorType
  • bInterfaceNumber
  • bAlternateSetting
  • bNumEndpoints
  • bInterfaceClass
  • bInterfaceSubClass
  • bInterfaceProtocol
  • iInterface
  • extra (Buffer containing any extra data or additional descriptors)

Endpoint

Common base for InEndpoint and OutEndpoint, see below.

.direction

Endpoint direction: usb.LIBUSB_ENDPOINT_IN or usb.LIBUSB_ENDPOINT_OUT.

.transferType

Endpoint type: usb.LIBUSB_TRANSFER_TYPE_BULK, usb.LIBUSB_TRANSFER_TYPE_INTERRUPT, or usb.LIBUSB_TRANSFER_TYPE_ISOCHRONOUS.

.descriptor

Object with fields from the endpoint descriptor -- see libusb documentation or USB spec.

  • bLength
  • bDescriptorType
  • bEndpointAddress
  • bmAttributes
  • wMaxPacketSize
  • bInterval
  • bRefresh
  • bSynchAddress
  • extra (Buffer containing any extra data or additional descriptors)

InEndpoint

Endpoints in the IN direction (device->PC) have this type.

.transfer(length, callback(error, data))

Perform a transfer to read data from the endpoint.

If length is greater than maxPacketSize, libusb will automatically split the transfer in multiple packets, and you will receive one callback with all data once all packets are complete.

this in the callback is the InEndpoint object.

.startStream(nTransfers=3, transferSize=maxPacketSize)

Start a streaming transfer from the endpoint.

The library will keep nTransfers transfers of size transferSize pending in the kernel at all times to ensure continuous data flow. This is handled by the libusb event thread, so it continues even if the Node v8 thread is busy. The data and error events are emitted as transfers complete.

.stopStream()

Stop the streaming transfer.

Further data may still be received. The end event is emitted once all transfers have completed or canceled.

Event: data(data : Buffer)

Emitted with data received by the stream

Event: error(error)

Emitted when the stream encounters an error.

Event: end

Emitted when the stream has been canceled

OutEndpoint

Endpoints in the OUT direction (PC->device) have this type.

.transfer(data, callback(error))

Perform a transfer to write data to the endpoint.

If length is greater than maxPacketSize, libusb will automatically split the transfer in multiple packets, and you will receive one callback once all packets are complete.

this in the callback is the OutEndpoint object.

.startStream(nTransfers=3, transferSize=maxPacketSize)

Start a streaming transfer to the endpoint.

The library will help you maintain nTransfers transfers pending in the kernel to ensure continuous data flow. The drain event is emitted when another transfer is necessary. Your drain handler should use the .write() method to start another transfer.

.write(data)

Write data to the endpoint with the stream. data should be a buffer of length transferSize as passed to startStream.

Delegates to .transfer(), but differs in that it updates the stream state tracking the number of requests in flight.

.stopStream()

Stop the streaming transfer.

No further drain events will be emitted. When all transfers have been completed, the OutEndpoint emits the end event.

Event: drain

Emitted when the stream requests more data. Use the .write() method to start another transfer.

Event: error(error)

Emitted when the stream encounters an error.

Event: end

Emitted when the stream has been stopped and all pending requests have been completed.

Development and testing

To build from git:

git clone https://github.com/nonolith/node-usb.git
cd node-usb
npm install

To execute the unit tests, CoffeeScript is required. Run

npm test

Some tests require an attached USB device -- firmware to be released soon.

Limitations

Does not support:

  • Configurations other than the default one
  • Isochronous transfers
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