As the first of the prototype PCB's started rolling in, it became clear that some minor tweaks were needed to help keep things super-simple. The prototype boards are very encouraging! More on that soon! The proposed changes optimize the most commonly used connectors in the specification to reduce the need for numerous voltage regulators & further refine clean signal support.
* Adds dedicated common bus for digital signals on many connectors.
* Revises main connectors to support 6 & 40 volts max contacts.
* Adds support for balanced audio on main 25 contact connectors.
That last item is super-important. More & more dev boards feature analog audio playback capabilities, but the audio is typically rather noisy. Even analog audio from a higher-quality source is often negatively affected by nearby digital signals. Ideally a broadcast-quality digital audio protocol should be used, such as AES (or a board-to-board protocol like I2S). Unfortunately, the flat modular topology of Retro Modules does not support those signals (two boards emitting I2S on a shared bus is a big problem). A suitable work-around is to use balanced line-level analog audio signal, which is used by audio professionals worldwide. Balanced audio DAC boards (and amps supporting balanced audio) are readily available & inexpensive.