Losing ERP triggers with E-Prime

[Don.Rojas at UCHSC.edu]

Yes, it might be viable.  If you are using a Writeport command, you need
to leave whatever parallel port bits you are toggling on for a while
before writing zeros to the port to turn off the trigger.  How long the
trigger needs to be depends on your specific acquisition, but 30 to 50
ms is usually ok with our Neuroscan EEG acquisitions.  Try using an
in-line trigger sequence like this:

TimerDuration = .03
StartTime = Timer

do
	WritePort &H0378, 1
Loop Until Timer > StartTime + TimerDuration

WritePort &H0378, 0


-----Original Message-----
From: eprime at mail.talkbank.org [mailto:eprime at mail.talkbank.org] On
Behalf Of Richard P. Heitz
Sent: Friday, November 14, 2003 3:12 PM
To: E-Prime Listserv
Subject: Losing ERP triggers with E-Prime

That makes sense, but unfortunately, I am not using pre-release, nor is
the
response period any where near the display stimuli (temporally, that
is).
To further explore the problem, I wrote a simple program in E-Prime
using
the writeport command and an identical program in Presentation.
Presentation lost no triggers whereas E-Prime lost 7%, again randomly.
So,
I figure it has to be something about the way E-Prime is writing to the
parallel port.  Is my earlier speculation about a "pulse width" even
viable?