How to fix PyVISA not finding any ASRL (serial port) instruments


You are trying to connect to a USB instrument using PyVISA & pyvisa-py, but the PyVISA resource manager doesn’t find any instruments:

#!/usr/bin/env python3
import visa
rm = visa.ResourceManager()
print(rm.list_resources()) # Prints "()" => No instruments found!


Install PySerial 3.0+:

First you need to remove the system package python3-serial if installed. Example for Ubuntu/Debian:

sudo apt remove python3-serial

and also remove the pip serial package if installed (we need to install pyserial, not serial!)

sudo pip3 uninstall serial

Then install pyserial:

sudo pip3 install pyserial

You can check if PySerial is installed properly using

python3 -m visa info

It should show you

ASRL INSTR: Available via PySerial (3.4)

if pyserial is installed correctly!

Note: The commands above are for Python 3.x. In case you are still using Python 2.x use pip2 or pip instead of pip3 and use python-serial instead of python3-serial as APT package name.