Sending ttl code to ASL eyetracker data file

[sadler]

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

[sadler]

It turns out that not only is the ttl code not recognized by the receiving computer from the file that I wrote but it will also not be recognized from the sendTTL sample file included in DirectRT. However, the receiving computer will recognize and encode a ttl code if it is send from the I/O test. Thus, this seems to be a DirectRT problem. Any advice would be greatly appreciated as it is critical that I am able to send ttl codes.

Thanks,
Scott

[sadler]

It turns out that the ASL software for encoding the ttl code received from DirectRT in the eye data file requires that the ttl code be sent out as a pulse. Leaving the ttl code on the port for any period of time, even 10 msec, results in it not being recorded by the ASL software. This is why the I/O TTL test worked (it sends a pulse), but my input file and the sample sendTTL input file did not work (both had time values for the ttl code set to 10 msec). I do not know why this is the case but it is. So, when the time value is set 0, there are no problems and the ttl code is recorded in the ASL eye data file.

Scott

[jarvis24]

That is very useful info to have Scott, thank you for the update. I'm sure other eye-tracker researchers will find this useful if they run into the same issue.

[JEC]

Thanks for posting!