After going through all the install steps for your OS, run these checks as simple tests to make sure everything is installed correctly. See the rest of the page for some potential hiccups you may run into.

Go ahead and plug in your MCP2221 to a USB port on your PC.

Most of these tests are done via the Python REPL, at the >>> prompt. To get there, simply launch Python:

$ python3
Python 3.6.9 (default, Nov  7 2019, 10:44:02) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

Check that hidapi is installed correctly

At the Python REPL, type:

import hid

You should get a dump of everything attached to your USB ports.

Check that MCP2221 can be found

At the Python REPL, type:

import hid
device = hid.device(), 0x00DD)

it should run without any errors:

If for some reason the MCP2221 can not be found, you might see something like this:

Check your USB cable connection.

Check environment variable within Python

At the Python REPL, type:

import os

If you get a KeyError it means you did not set the environment variable right:

If you have set it correctly, you'll get a value back:

This guide was first published on Dec 22, 2019. It was last updated on Nov 27, 2023.

This page (Post Install Checks) was last updated on Dec 17, 2019.

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