Roland MC-300 / 500 / Mk2 Drive Upgrade (Part 2)

Follow-up to Roland upgrade tutorial highlighting issues with Gotek drive emulator and offering solutions. Used to have all the info in annotations, but since youtube got rid of them, now all the labels are missing.

Mod 1: Switch to disable USB drive without ejecting it.
Mod 2: Switch or push-button, emulating floppy eject signal.
Mod 3: Auto-increment function.
Each step is optional depending on what new function you want to get.

Augmented schematics (additions in red):
http://www.enilenis.com/projects/mc30...

PCB layout:
http://www.enilenis.com/projects/mc30...

ATtiny85/45, Digispark or Adafruit Trinket sketch:
http://www.enilenis.com/projects/mc30...

Gotek IMG archive for Roland devices:
http://www.enilenis.com/projects/mc30...

Tiny AVR Programmer used in this video:
https://www.sparkfun.com/products/11801

ATtiny85 microprocessor:
https://www.sparkfun.com/products/9378

Parts needed for all 3 mods:
1x toggle switch with or without a LED indicator.
1x 220k resistor, if the LED is present.
1x ATtiny85, or ATtiny45, or Digispark, or Adafruit Trinket microcontroller.

Note: there is a 1k through-hole resistor that I used to link +5v USB line to the output pad of RN6. I wanted to use the original surface mount part by lifting it and soldering onto the pad vertically, but I accidentally broke it. Any resistor 1k-10k will work fine should you run into a similar problem.