Alternative Arduino firmware to act as a TCBM<->Serial<->USB bridge

[ytmytm]

Idea from: https://plus4world.powweb.com/forum/50827

Instead of simulating 1551 over SD card the Arduino could simply act as a bridge between TCBM bus and Serial/USB connected to a RPi (or a PC) through Arduino's programming header.

The simulation part would happen on that end.

This is not yet a Pi1541 / Pi1551 level due to Serial port lag and jitter. Also TCBM activity would be encapsulated in some kind of protocol, there is no connection to TCBM header.

Pros:

• much faster development cycle for testing on real hardware: moving software faster than copying to SD card and moving SD card around

Cons:

• Arduino Mini's maximum speed is 57600 baud, not even 115200 - this is slower than fastload protocol
• New software has to be written for PC side