USB Library for Node.JS

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 0.6.12/Linux and 0.8.14/Linux.

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

Installation

Make sure you have installed libusb-1.0-0-dev (Ubuntu: sudo apt-get install libusb-1.0-0-dev).

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.

.devices

List of Device objects for the USB devices attached to the system.

.LIBUSB_*

Constant properties from libusb

.setDebugLevel(level : int)

Set the libusb debug level (between 0 and 4)

Device

Represents a USB device.

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

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.

.interface(interface=0, altsetting=0)

Return the interface with the specified index and alternate setting.

.interfaces

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

.timeout

(property getter/setter) Timeout in milliseconds to use for controlTransfer and endpoint transfers.

.deviceAddress

Integer USB device address

.busNumber

Integer USB device number

.reset(callback)

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

.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 config descriptor:

bLength
bDescriptorType
wTotalLength
bNumInterfaces
bConfigurationValue
iConfiguration
bmAttributes
MaxPower
extra: Buffer containing additional data

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.

.claim()

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

.release(callback)

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

.detachKernelDriver()

Detaches the kernel driver from interface.

.attachKernelDriver() : undefined

Re-attaches the kernel driver to interface.

.isKernelDriverActive()

Returns 0 if not active; 1 if active.

Descriptor attributes

Fields from the interface descriptor, see libusb documentation or USB spec.

bLength
bDescriptorType
bInterfaceNumber
bAlternateSetting
bNumEndpoints
bInterfaceClass
bInterfaceSubClass
bInterfaceProtocol
iInterface
extraData : Buffer

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_BULK, usb.LIBUSB_TRANSFER_INTERRUPT, or usb.LIBUSB_TRANSFER_ISOCHRONOUS.

.maxPacketSize

The max packet size.

.maxIsoPacketSize

The max isochronous packet size if transfer type is isochronous.

Descriptor attributes

Fields from the interface descriptor, see libusb documentation or USB spec.

bLength
bDescriptorType
bEndpointAddress
bmAttributes
wMaxPacketSize
bInterval
bRefresh
bSynchAddress
extra_length
extraData : Buffer

InEndpoint

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

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

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(data, 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.

Callback first parameter is data, just like InEndpoint, but will always be undefined as no data is returned.

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

License

sysrun/node-usb

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