synchronize event markers with refresh rate

[Paul Groot]

Hi Hank,

The event markers should be in sync when you prepare the markers using
the following functions:

Stim.OffsetSignalEnabled = True
Stim.OnsetSignalEnabled = True
Stim.OffsetSignalPort = &H378
Stim.OnsetSignalPort = &H378
Stim.OffsetSignalData = &H00
Stim.OnsetSignalData = &HFF  ' < this is your onset code in hexadedimal notation

Where Stim is your display object.

Most flatscreens have an onset delay of a few milliseconds, so this
would be a fixed delay caused by the properties of the display.

Best,
Paul

2011/3/29 Hank Jedema <Jedema at pitt.edu>:
> Hi All,
>
> I am trying to run a stop signal response task while recording
> electrophysiological activity on another setup. In order to get
> synchronization of behavior with the timing of my recordings, I have E-
> prime sent out event markers via the parallel port to an input of my
> recording device. It seems that this works well responses, but it
> seems that E-prime sends out the event markers for the display of
> stimuli before the stimulus actually appears on the screen: the
> eventmarker/timestamp is sent when the code issues the request for the
> stimulus to appear, rather than when the stimulus actually appears on
> the screen (i.e at the vertical blank/screen refresh after the
> stimulus.onset delay). Is there a way to get the event marker signal
> to synchronize with the actual appearance of the stimulus or is this
> something that can only be corrected offline by correcting the
> timestamps for stimulus appearance with their onset delay ?
>
> Thanks very much for your help.
>
> Hank
>
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