So I hooked up Sandwichlizard's plotter with my computer and wrote a program that plots a 32x32 particle time-space diagram of a Rule 90 (or any other) simulation with an initial state of 0x00000200. The program is easily configurable and can be compiled with rasm/rasmui.

The rule is embedded into the program as a constant (literally as "dw 90"), so it can be changed anytime.

Do check out the links embedded in the text above.

It doesn't really adhere to a protocol. As it is right now, I think you send the position as a 16-bit tuple (8 bits of X, 8 bits of Y) on port 1 and a 16-bit map on port 0 (each bit is plotted either as yellow (0) or blue (1) particle, that means 16 particles next to one another).

The old version would actually send single particle codes on port 0 and positions on port 1, but that was back then. Check the history.