Also could I get a sample of using SERIN?
I have tried this and it outputs the hello world and then waits there and never loops. So I can only assume that its not getting the "A" char when I try and send it.

InputSig var GPIO.0

loop:
SerOut Inputsig,N2400,["Hello World",13,10]
Serin InputSig,N2400,["A"]
Pause 200
GoTo loop