Rather than write a bunch of stepper motor code himself, he installed and ran a four-axis fork of grbl on the Arduino, turning it into a stepper motor controller.

[Part 1 begins a look at how to interface with some common robotics-type sensors and actuators, and how these can be tied into an example system (in this case, the author's E-2 Autonomous Submarine ...

An Arduino Mega 2560 clone is used to control four TB6600 stepper motor drivers, with a common OLED display module installed where the original display went.