I am trying to send a unique stimulus code via ttl from DirectRT to the computer running ASL eyetracker software to be included in the eye data file so that I can synchronize eye movements to stimulus onset. I have run the I/O tool and it can sent the appropriate byte information to the eyetracker computer and this code is recorded in the eye data file. However, when I make the call from the input file, nothing is recorded in the eye data file. What might be going wrong? Does the stim, loc, and time columns for the ttl code need to come before the stim, loc, time columns specifying the actual stimulus?

Scott