From time to time, an error occurs when working with CircuitPython. Here are a variety of errors that can happen, what they mean and how to fix them.

File system issues

If your host computer starts complaining that your CIRCUITPY drive is corrupted or files cannot be overwritten or deleted, then you will have to erase it completely. When CircuitPython restarts it will create a fresh empty CIRCUITPY filesystem.

Corruption often happens on Windows when the CIRCUITPY disk is not safely ejected before being reset by the button or being disconnected from USB. This can also happen on Linux and Mac OSX but it’s less likely.


To erase and re-create CIRCUITPY (for example, to correct a corrupted filesystem), follow one of the procedures below. It’s important to note that any files stored on the CIRCUITPY drive will be erased. Back up your code if possible before continuing!

REPL Erase Method

This is the recommended method of erasing your board. If you are having trouble accessing the CIRCUITPY drive or the REPL, consider first putting your board into safe mode.

To erase any board if you have access to the REPL:

  1. Connect to the CircuitPython REPL using a terminal program.

  2. Type import storage into the REPL.

  3. Then, type storage.erase_filesystem() into the REPL.

  4. The CIRCUITPY drive will be erased and the board will restart with an empty CIRCUITPY drive.

Erase File Method

If you do not have access to the REPL, you may still have options to erase your board.

The Erase CIRCUITPY Without Access to the REPL section of the Troubleshooting page in the Welcome to CircuitPython guide covers the non-REPL erase process for various boards. Visit the guide, find the process that applies to your board, and follow the instructions to erase your board.

ValueError: Incompatible .mpy file.

This error occurs when importing a module that is stored as a mpy binary file (rather than a py text file) that was generated by a different version of CircuitPython than the one it’s being loaded into. Most versions are compatible but, rarely they aren’t. In particular, the mpy binary format changed between CircuitPython versions 1.x and 2.x, 2.x and 3.x, and will change again between 6.x and 7.x.

So, for instance, if you just upgraded to CircuitPython 7.x from 6.x you’ll need to download a newer version of the library that triggered the error on import. They are all available in the Adafruit bundle and the Community bundle. Make sure to download a version with 7.0.0 or higher in the filename.