webusbtmc

WebUSBTMC is a USBTMC driver utilizing the WebUSB API.

What is USBTMC?

USBTMC is a device class specification for remotely controlling test and measurement instruments.
It is also used in VISA (Virtual Instrument Software Architecture) to communicate with instruments over USB.

A code example

You can read identifying information from an instrument using the following code:

async function funcAsync() {
  const tmc = new Webusbtmc();
  const filters = [
    { 'classCode': 0xFE, 'subclassCode': 0x03, 'protocolCode': 0x01 },
  ];
  const device = await navigator.usb.requestDevice({ 'filters': filters });
  await tmc.open(device);
  await tmc.write('*IDN?');
  await tmc.delay(0.1); // just in case
  const result = await tmc.read();
  console.log(result);
  await tmc.close();
}

Practical examples

This repository contains practical examples using WebUSBTMC.

WebUSBTMC Test Panel

WebUSBTMC Test Panel is inspired by the "NI-VISA Interactive Control App".
It allows you to quickly check connectivity with your instruments.

WebUSBTMC with Blockly

WebUSBTMC with Blockly provides the simplest and easiest way to control your instruments.
You can write automation programs with Blockly and run them in a browser sandbox using the JS-Interpreter.

Take a Screenshot

Take a Screenshot is the easiest way to capture screenshots from your instruments.
You don't need additional flash drives. You can view the screenshots immediately and save them.

WebUSBTMC with SpeechRecognition

WebUSBTMC with SpeechRecognition is a voice control app using the SpeechRecognition API.

Unlock USB Modular Devices

Unlock USB Modular Devices is a supplemental tool.
Some Keysight (or Agilent) USB modular instruments remain in "firmware update" mode at power-on. This app can switch them from "firmware update" mode to USBTMC mode.

Setup

Windows

You need to install the WinUSB driver for your instrument using Zadig.
If you have already installed NI-VISA, Keysight IO Libraries Suite, or similar tools, replace the USBTMC driver with the WinUSB driver using Zadig.
You can uninstall the WinUSB driver if you want to restore the original USBTMC driver.
Don't forget to tick the "Delete the driver software for this device" checkbox.
Do not uninstall "USB Test and Measurement Devices".

Linux and Raspberry Pi

You may need to create a udev rule to grant access permission to the instrument.
There are many tutorials about udev rules for USB devices; please follow those instructions.

"/etc/udev/rules.d/99-usbtmc.rules" example

SUBSYSTEM=="usb", ACTION=="add", ATTRS{idVendor}=="xxxx", ATTRS{idProduct}=="yyyy", GROUP="zzzz", MODE="0660"

If you encounter the error "NetworkError: Unable to claim interface", you must unbind your device:

user@host:~$ ls /sys/bus/usb/drivers/usbtmc/
2-3:1.0  bind  module  new_id  remove_id  uevent  unbind
user@host:~$ sudo sh -c "echo -n 2-3:1.0 > /sys/bus/usb/drivers/usbtmc/unbind"
user@host:~$ ls /sys/bus/usb/drivers/usbtmc/
bind  module  new_id  remove_id  uevent  unbind

To avoid unbinding your device every time you connect it, consider blacklisting the USBTMC module.

"/etc/modprobe.d/blacklist.conf" example

# for webusbtmc
blacklist usbtmc

macOS

No special setup is necessary.

Android

You only need an OTG cable.

Run on Your Computer

I recommend using VS Code with the Live Server extension.
Download this repository, open the unzipped folder in VS Code, and run Live Server.