usb-cdc-acm

Userspace javascript implementation of a USB CDC ACM driver, on top of libusb.

This is part of Nordic Semiconductor's javascript tools to interface with nRF SoCs and development kits. Although USB CDC ACM is part of the USB specifications and a de facto standard when it comes to emulating a serial port connection on an embedded device, Nordic Semiconductor cannot offer support for other hardware platforms. This software is provided "as is".

Motivation

Sometimes you want to fetch info from the USB descriptors via the NodeJS usb module, and at the same time use the CDC ACM interface to send and receive data. But this is not possible with some host configurations (notably, win32/win64 platforms and their need to manually switch the driver via Zadig or the like).

API

usb-cdc-acm provides a duplex Stream interface. Please refer to NodeJS's documentation about Streams for a full API spec.

Other than that, usb-cdc-acm provides two entry points. Either of those need you to use usb to fetch a reference to the Device or to a CDC Interface.

Use the factory method when your USB device only has one CDC ACM interface:

var usb = require('usb');
const UsbCdcAcm = require('usb-cdc-acm');

var device = usb.findByIds( 0x1915, 0x520f ); // VID/PID for Nordic Semi / USB CDC demo

// The device MUST be open before instantiating the UsbCdcAcm stream!
device.open();

// An options object with the baud rate is optional.
let stream = UsbCdcAcm.fromUsbDevice(device, { baudRate: 1000000});

// Then, use it as any other Stream
stream.on('data', function(data) { console.log('recv: ', data); });
stream.write('Hello world!');

// Remember to destroy the stream and close the device when finished!
// Failure to do so might leave the USB device in an ususable state for other applications.
setTimeout(function(){ 
    stream.destroy();
    device.close();
}, 5000);

If the device has several CDC ACM interfaces and finer control is needed,

// An options object with the baud rate is optional.
let stream = new UsbCdcAcm(device.interfaces[0], { baudRate: 1000000});

For a more complete example, check the test/test.js file.

Legal

Distributed under a BSD-3 license. See the LICENSE file for details.