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VISA USB Troubleshooting

VISA (Virtual Instrument Software Architecture) is a standardized interface for communcating with test and measurement instruments, such as oscilloscopes and multimeters. Many possible connection types are possible including: GPIB, TCP/IP (ethernet), and USB. For USB connections, some changes may be required on your computer in order for Flojoy (and Python in general) to connect to the instrument. This guide will cover those changes. Other guides are in progress for other connection types.

Only proceed if you are sure your device does not appear with the following Python script (requires pyvisa and pyvisa-py packages):

import pyvisa
rm = pyvisa.ResourceManager('@py')


For Unix systems, it may be required to allow non-root access to USB ports. You can do this for all device with the terminal command:

sudo echo 'SUBSYSTEM=="usb", MODE="0666", GROUP="usbusers"' >> /etc/udev/rules.d/99-com.rules

Or, you can allow root access on a per-device basis by following this tutorial:


For Windows, the only change that should be required is to install a generic USB driver for the instrument. Note that if a specific driver is already installed (e.g. TekVISA), it must be overwritten. There are two ways to accomplish this:

  1. Download Zadig and replace/install the driver (mostly) automatically.
  2. Manually download the driver and install it in Device Manager.

In both methods ensure your device is plugged in and showing up in Device Manager.

1. Zadig Method

Detailed Instructions


  • Install Zadig (v2.8 as of Sept-22-2023)
  • Run zadig-2.8.exe
  • Find your device in the top dropdown menu.
  • If a driver is already installed, you may need to press Options -> List All Devices.
  • Choose WinUSB (> v6.1) to the right of the green arrow.
  • Press Install Driver.
  • You may need to restart your system for the changes to work.

You may also have to place the libusb-1.0.dll file in C:/Windows/System32 as described below.

2. Manual Method

You must first download the file libusb-1.0.dll:

  •, go to Downloads, Latest Windows Binaries
  • This should download libusb-1.0.26-binaries.7z. Extract or open this file.
  • In /libusb-1.0.26-binaries/VS2015-x64/dll copy libusb-1.0.dll.
  • Place this in C:/Windows/System32.

You must then chose the driver to install for the device.

  • First go to Device Manager (e.g. by using the start menu search bar)
  • Find the device. If no driver is install it will likely appear under Other devices.


  • Right click on the device and select Update Driver.
  • In the new window press Browse my computer for drivers,
  • and then Let me pick ... at the bottom.

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  • Press Universal Serial Bus devices.
  • In the left box click WinUSB Device,
  • and in the right box click WinUSB Device.
  • Click Next and install the driver.

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You likely will have to allow USB non-root access such as in the Linux section above. There may be other changes necessary as well.