In the process of updating the guide for this driver (at https://learn.adafruit.com/micropython-hardware-charlieplex-led-matrix/overview ) I saw it was slightly experimental and unfinished (fill only hit a 4x4 matrix and was randomly turning LEDs on/off). This release swaps back to the micropython-adafruit-is31fl3731 API that has been updated to work with the current CircuitPython release (2.0). This includes support for fill, pixel brightness and blinking, and frame swaps. The in-progress / experimental code from the previous version is now available in the 'experimental' branch of this repository.