Hi guys if you look closely you'll find that the schematics for M5Atom Matrix and M5Atom Lite are not completely the same. Apart from the RGB LEDs (25 vs 1) only the M5Atom Matrix has an MPU6886 internally which is controlled via I2C using GPIO21 and GPIO22. However with the ATOM Stepper Motor Driver GPIO21 and GPIO22 are used for RST (Reset) and EN (Enable). Therefore only M5Atom Lite can be used to control the ATOM Stepper Motor Driver. Thanks Felix