Sending responses via TTL (case 5907)

[AaronNewman]

Hi

I am using DirectRT to present stimuli in an event-related potential (ERP) experiment. Codes for each stimulus and response have to be sent via TTL to the ERP recording computer so that we can both time-lock ERP responses to stimuli and (importantly) sort ERP responses bsed on whether the subject's response was correct or not. While I've figured out how to send a code via TTL after a response, thus telling the ERP equipment WHEN a response occurred, I can't see any way to send a TTL pulse that codes WHAT key was pressed. It seems that you have to specify the TTL code in advance. Ideally what I would like is something similar to the "feedback" code that you can put in the Stim column to show the last keypress to the subject, but sending that code to the TTL rather than the screen. I tried "ttl:feedback" and "ttl:=" but these didn't work.

Is it currently possible to do this? Or, could you implement it? It's absolutely essential for using DirectRT in ERP experiments in which we're collecting subject responses.

thanks
Aaron