The 486 that [someyob] is restoring had the Turbo button, but sadly there was just a simple LED to show whether or not it was engaged.

Chapter 1, page 11 This code is basic but allows the reader to gain insight into key elements for several other projects in this book. It combines two pieces of code that are listed in the examples ...

Using a USB-C phone with Power Delivery is ideal here, as it allows the phone to be powered while also communicating with the Arduino over USB. The RemoteXY app is built specifically for this purpose.