To help you get started, we've collected the most common ways that usb is being used within popular public projects.

USB Library for Node.JS

Node.JS library for communicating with USB devices.

This is a refactoring / rewrite of Christopher Klein's node-usb.

Prerequisites

Node.js >= v10.20.0, which includes npm.

Windows

On Windows, if you get LIBUSB_ERROR_NOT_SUPPORTED when attempting to open your device, it's possible your device doesn't have a WinUSB driver for libusb to use.

You can install one using Zadig or another approach is to use the UsbDK Backend of libusb by immediately calling usb.useUsbDkBackend().

Note that you cannot use multiple drivers on Windows as they get exclusive access to the device. So if you want to switch between drivers (e.g. using a printer with this software or the system), you will need to uninstall/install drivers as required.

For further info, check How to use libusb on Windows in the libusb's wiki.

Linux

On Linux, you'll need libudev to build libusb if a prebuild is not available. On Ubuntu/Debian:

sudo apt-get install build-essential libudev-dev

You may need to modify your udev and permission rules in order to access your desired device. Along the lines of:

SUBSYSTEM=="usb", ATTR{idVendor}=="USB-VENDOR-ID", ATTR{idProduct}=="USB-PRODUCT-ID", MODE="0660", GROUP="GROUP-YOUR-USER-IS-IN"

Troubleshooting

For libusb issues, please refer to the FAQ at https://github.com/libusb/libusb/wiki/FAQ

Installation

Native modules are bundled using prebuildify, so installation should be as simple as installing the package.

With npm:

npm install usb

With yarn:

yarn add usb

Note: the library is now written in TypeScript, so a separate types file is not longer required to be installed (e.g. don't install @types/usb).

License

MIT

Note that the compiled Node extension includes libusb, and is thus subject to the LGPL.

Limitations

Does not support:

• Configurations other than the default one
• Isochronous transfers

Getting Started

Use the following examples to kickstart your development. Once you have a desired device, use the APIs below to interact with it.

Migrating to v2.0.0

The legacy API exists on an object called usb on the main import and the convenience functions exist as top level objects.

To use v2.0.0 simply update your import statements and the function calls;

// import * as usb from 'usb';
// const devices: usb.Device[] = usb.getDeviceList();

import { usb, getDeviceList } from 'usb';
const devices: usb.Device[] = getDeviceList();

List all legacy devices

import { getDeviceList } from 'usb';

const devices = getDeviceList();

for (const device of devices) {
    console.log(device); // Legacy device
}

Find legacy device by vid/pid

import { findByIds } from 'usb';

const device = findByIds(0x59e3, 0x0a23);

if (device) {
    console.log(device); // Legacy device
}

Find legacy device by SerialNumber

import { findBySerialNumber } from 'usb';

(async () => {
    // Uses a blocking call, so is async
    const device = await findBySerialNumber('TEST_DEVICE');

    if (device) {
        console.log(device); // Legacy device
    }
})();

Turn legacy Device into WebUSB compatible device

import { findBySerialNumber, WebUSBDevice } from 'usb';

(async () => {
    // Uses a blocking call, so is async
    const device = await findBySerialNumber('TEST_DEVICE');

    // Uses blocking calls, so is async
    const webDevice = await WebUSBDevice.createInstance(device);

    if (webDevice) {
        console.log(webDevice); // WebUSB device
    }
})();

Use WebUSB approach to find a device

import { webusb } from 'usb';

(async () => {
    // Returns first matching device
    const device = await webusb.requestDevice({
        filters: [{}]
    })

    console.log(device); // WebUSB device
})();

Use WebUSB approach to find a device with custom selection method

import { WebUSB } from 'usb';

(async () => {
    const customWebUSB = new WebUSB({
        // This function can return a promise which allows a UI to be displayed if required
        devicesFound: devices => devices.find(device => device.serialNumber === 'TEST_DEVICE')
    });

    // Returns device based on injected 'devicesFound' function
    const device = await customWebUSB.requestDevice({
        filters: [{}]
    })

    console.log(device); // WebUSB device
})();

Use WebUSB approach to list authorised devices

import { webusb } from 'usb';

(async () => {
    // The default webusb instance follows the WebUSB spec and only returns authorised devices
    const devices = await webusb.getDevices();

    for (const device of devices) {
        console.log(device); // WebUSB device
    }
})();

Use WebUSB approach to list all devices

import { WebUSB } from 'usb';

(async () => {
    const customWebUSB = new WebUSB({
        // Bypass checking for authorised devices
        allowAllDevices: true
    });

    // Uses blocking calls, so is async
    const devices = await customWebUSB.getDevices();

    for (const device of devices) {
        console.log(device); // WebUSB device
    }
})();

Electron

Please refer to the maintained example for using node-usb in electron:

https://github.com/node-usb/node-usb-example-electron

If using a packaging system for electron, ensure the node-usb library does not get recompiled as the correct binaries are already shipped with the package. For example, for electron-builder, use these settings:

• buildDependenciesFromSource: true
• nodeGypRebuild: false
• npmRebuild: false

APIs

Since v2.0.0, the node-usb library supports two APIs:

• WebUSB which follows the WebUSB Specification (recommended)
• Legacy API which retains the previous 'non-blocking' API

Convenience methods also exist to easily list or find devices as well as convert between a legacy usb.Device device and WebUSB device.

Full auto-generated API documentation can be seen here:

https://node-usb.github.io/node-usb/

Convenience Functions

getDeviceList()

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

findByIds(vid, pid)

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

findBySerialNumber(serialNumber)

Convenience method to get a promise of the legacy device with the specified serial number, or undefined if no such device is present.

getWebUsb()

Return the navigator.usb instance if it exists, otherwise a webusb instance.

WebUSBDevice

WebUSB Device class for wrapping a legacy Device into a WebUSB device

WebUSBDevice.createInstance(device)

Convenience method to return a promise of a WebUSB device based on a legacy device

WebUSB

Please refer to the WebUSB specification which be found here:

https://wicg.github.io/webusb/

Implementation Status

USB

• [x] getDevices()
• [x] requestDevice()

USBDevice

• [x] usbVersionMajor
• [x] usbVersionMinor
• [x] usbVersionSubminor
• [x] deviceClass
• [x] deviceSubclass
• [x] deviceProtocol
• [x] vendorId
• [x] productId
• [x] deviceVersionMajor
• [x] deviceVersionMinor
• [x] deviceVersionSubminor
• [x] manufacturerName
• [x] productName
• [x] serialNumber
• [x] configuration
• [x] configurations
• [x] opened
• [x] open()
• [x] close()
• [x] selectConfiguration()
• [x] claimInterface()
• [x] releaseInterface()
• [x] selectAlternateInterface()
• [x] controlTransferIn()
• [x] controlTransferOut() - bytesWritten always equals the initial buffer length
• [x] transferIn()
• [x] transferOut() - bytesWritten always equals the initial buffer length
• [x] clearHalt()
• [x] reset()
• [ ] isochronousTransferIn()
• [ ] isochronousTransferOut()
• [ ] forget()

Events

• [x] connect
• [x] disconnect

Legacy API

usb

Legacy usb object.

usb.LIBUSB_*

Constant properties from libusb

usb.getDeviceList()

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

usb.pollHotplug

Force polling loop for hotplug events.

usb.setDebugLevel(level : int)

Set the libusb debug level (between 0 and 4)

usb.useUsbDkBackend()

On Windows, use the USBDK backend of libusb instead of WinUSB

Device

Represents a USB device.

.busNumber

Integer USB device number

.deviceAddress

Integer USB device address

.portNumbers

Array containing the USB device port numbers, or undefined if not supported on this platform.

.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)

.allConfigDescriptors

Contains all config descriptors of the device (same structure as .configDescriptor above)

.parent

Contains the parent of the device, such as a hub. If there is no parent this property is set to null.

.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.

A package is available to calculate bmRequestType if needed.

.setConfiguration(id, callback(error))

Set the device configuration to something other than the default (0). To use this, first call .open(false) (which tells it not to auto configure), then before claiming an interface, call this method.

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

Perform a control transfer to retrieve a string descriptor

.getBosDescriptor(callback(error, bosDescriptor))

Perform a control transfer to retrieve an object with properties for the fields of the Binary Object Store descriptor:

• bLength
• bDescriptorType
• wTotalLength
• bNumDeviceCaps

.getCapabilities(callback(error, capabilities))

Retrieve a list of Capability objects for the Binary Object Store capabilities of the device.

.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 control 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([closeEndpoints], callback(error))

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

It is an error to release an interface with pending transfers. If the optional closeEndpoints parameter is true, any active endpoint streams are stopped (see Endpoint.stopStream), and the interface is released after the stream transfers are cancelled. Transfers submitted individually with Endpoint.transfer are not affected by this parameter.

.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)

Capability

.type

Integer capability type.

.data

Buffer capability data.

.descriptor

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

• bLength
• bDescriptorType
• bDevCapabilityType

Endpoint

Common base for InEndpoint and OutEndpoint, see below.

.direction

Endpoint direction: "in" or "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)

.timeout

Sets the timeout in milliseconds for transfers on this endpoint. The default, 0, is infinite timeout.

.clearHalt(callback(error))

Clear the halt/stall condition for this endpoint.

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.

.startPoll(nTransfers=3, transferSize=maxPacketSize)

Start polling 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.

.stopPoll(cb)

Stop polling.

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

Event: data(data : Buffer)

Emitted with data received by the polling transfers

Event: error(error)

Emitted when polling encounters an error. All in flight transfers will be automatically canceled and no further polling will be done. You have to wait for the end event before you can start polling again.

Event: end

Emitted when polling 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.

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.

UsbDetection

usb.on('attach', function(device) { ... });

Attaches a callback to plugging in a device.

usb.on('detach', function(device) { ... });

Attaches a callback to unplugging a device.

usb.refHotplugEvents();

Restore (re-reference) the hotplug events unreferenced by unrefHotplugEvents()

usb.unrefHotplugEvents();

Listening to events will prevent the process to exit. By calling this function, hotplug events will be unreferenced by the event loop, allowing the process to exit even when listening for the attach and detach events.

Migrating from node-usb-detection

If you have been referred here by node-usb-detection, the following may be helpful for you to update your existing code.

usbDetect.startMonitoring() & usbDetect.stopMonitoring()

There is no direct equivalent to these methods. This is handled automatically for you when you add and remove event listeners.

You may find usb.unrefHotplugEvents() useful as it is intended to help with exit conditions.

usbDetect.find()

You can instead use usb.getDeviceList(). Be aware that this will do an enumeration to find all of the devices, and not look at a cache of the known devices. If you call it too often it may have a performance impact.

To find a specific device by vid and pid, call usb.findByIds. e.g. usb.findByIds(0x12, 0x34).

usbDetect.on('add', function(device) { ... })

These should be changed to usb.on('attach', function(device) { ... }).

There is no equivalent to filter based on the vid or pid, instead you should do a check inside the callback you provide.
The contents of the device object has also changed.

usbDetect.on('remove', function(device) { ... })

These should be changed to usb.on('detach', function(device) { ... }).

There is no equivalent to filter based on the vid or pid, instead you should do a check inside the callback you provide.
The contents of the device object has also changed.

usbDetect.on('change', function(device) { ... })

There is no direct equivalent to this. Instead you can listen to both attach and detach to get the same behaviour.

Development

The library is based on native bindings wrapping the libusb library.

Setup

Libusb is included as a submodule, clone this repository and then the submodule as follows:

git clone https://github.com/node-usb/node-usb
cd node-usb
git submodule update --init

Building

The package uses prebuildify to generate the native binaries using an install script and TypeScript for the binding code using the compile script. The package can be built as follows:

yarn
yarn compile

The native binaries can be rebuilt with:

yarn rebuild

Note: On Linux, you'll need libudev to build libusb. On Ubuntu/Debian:

sudo apt-get install build-essential libudev-dev

Testing

To execute the unit tests, Run:

yarn test

Some tests require an attached STM32F103 Microprocessor USB device with specific firmware.

yarn full-test
yarn valgrind

Releasing

Please refer to the Wiki for release instructions.