I want to start a trial when subject is fixating on the fixation cross. I want to combine the signal of fixation given by the eye-tracker to use in the e-prime program.
Here is the most simple code to send an “on-off” signal from an ASL eye tracker from eye prime. I assume you are using the parallel ports on the two machines (the e-prime presentation computer and the ASL computer) to communicate
1. put an inline object in E-prime at the beginning of the session procedure. The script in the inline object should read: WritePort &H378,0
this simply tells the ASL machine to set the port to 0. This code is not necessary on all systems.
2. Just before you want the ASL machine to record eye-dat data, insert an inline object with the script: WritePort &H378, 64 + 128 + c.getAttrib("SendXdat")
This simply tells ASL to set the data collection to ‘on’ You will need to put an Attribute in the list form which e-prime is drawing stimuli call SendXdat. (you can use any name you want for the attribute. I use SendXdat so I know exactly what it is). I often then use the SendXdat attribute as a stimulus type/condition identifier.
3. When you want the eye-dat data to stop collection, insert an inline object with the script: WritePort &H378, 0
telling the ASL system to stop collecting data.
with some systems the stop script should read" WritePort &H378, 64 + c.getAttrib("SendXdat")
but the 0 code usually does the trick.
Please let me know if this is useful or if you have questions. I have more complex code that I can share.