Dreamcast Parallel Port Mods?

My goodness... It is 2:34 AM right now.
TL;DR: Asking around to see if anyone has any experience with modding the parallel port.

So I have been doing a lot of research lately (lately = past 5 hours straight) into all sorts of Dreamcast mods. The things that I am most interested in are ones having to do with hardcore homebrew hardware/software. i.e. a coder's cable for the serial port (which I am currently gathering parts to build) OR (and this is amazing imo) the work that jj1odm did with the Dreamcast's parallel/g2 port: http://jj1odm.sizious.com/g2bus.html

This is awesome and I am looking into building a couple mods using the port myself, but unfortunately I am completely new to the DC modding scene. I know basic software stuff like C and such. My hardware knowledge is okay. I just wanted to ask around and see if anyone has had any experience doing mods/homebrew using the parallel port and if they had any advice or resources that could be helpful.
Sorry if this post is awkward (it's my first time! )

Thanks,
~Mitch (ByteFreak)

 

I've had a play with it - the asynchronous mode (what jj1odm calls "simple bus mode") is very easy to get working - you can basically connect any chip that has an 8080 type bus interface to it with minimal glue logic - the main restriction is that it's slow and can only handle 8 bit transfers.

The synchronous mode is substantially more complicated - on a practical level you are going to have to use at least a CPLD to interface with it - the address is sent out in two phases timed by the system clock and your device has to generate the correct bus timing signals.

 

Ah, thanks. I think I'll focus on making my coder's cable (using a ft232rl-5v usb cable with a logic level converter to 3.3v) for now. I want to first get a hang of writing basic homebrew software before I start interfacing with actual devices.

 

Recent versions of RT232RL doesn't need a separate level converter circuit, it can operate with 3,3V directly.
You can use a pre-made board like this, it has a jumper set so that you can choose between 3,3 or 5 volts: