Let's Make Robots!

Parallel port control for a Mac

Anyone have experience with controlling a parallel (8 or more lines) output on a Mac (OS X)? I want to control my CNC machine with a parallel interface but Macs don't have parallel ports anymore. I need to find a suitable replacement, but a serial port/MCU would drastically complicate things. Please help! What hardware should I get?

RS232 Communication with MCU

So I am making my own CNC - PCB Miller. It is communicating with the computer using RS232 (UART), but in my testing, I find that I don't always get the correct characters, even at 1200baud. Does anyone have a method to suggest for error-checking an incoming data string over serial? I was thinking of doing something like this:

CPU sends data to MCU 4 times.

MCU checks to make sure the data is repeated exactly 4 times.

--If yes->send "OK" 4 times

--If no->send "NOT OK" 4 times

If CPU receives OK, queue up the next data to send