synchronize event markers with refresh rate

Thu Apr 14 20:34:36 UTC 2011

Hank,

(Hmm, I see OnsetDelay, OnsetSignalData, OnsetSignalEnabled, and 
OnsetSignalPort, but no OnsetSignalDelay, so not sure what you are 
referring to there.  But no matter...)

Yes, both OnsetSignal... and WritePort can handle all 8 bits of any 
digital I/O port.  For more background information on how to 
generally handle multiple digitital I/O bits, please read "Parallel 
Port Complete" by Jan Axelson 
(http://www.amazon.com/Parallel-Port-Complete-Programming-Interfacing/dp/0965081915/ref=sr_1_1?ie=UTF8&s=books&qid=1302813230&sr=1-1 
), or just Google around.

-- David McFarlane, Professional Faultfinder

At 4/13/2011 03:27 PM Wednesday, you wrote:
>Thanks Paul. I did incorporate your recommendation into my program.
>However, there are still some issues unresolved. So I use the
>OnsetSignalDelay command for the event markers associated with the
>appearance of stimuli on the screen and I still use the writeport
>command to send event markers associated with the timing of touch
>screen responses. Can the OnsetSignalDelay command address multiple
>"pins" (OnsetSignalData) in its output ?
>The signal that E-prime sends to the other PC is actually an "8-bit
>strobe" which requires a "strobe signal" to be sent immediately after
>the 8-bit strobe. Currently it seems that the strobed event marker is
>not received until the end of the actual stimulus because the strobe
>signal is not received until an inline immediately after the stimulus.
>Is there a way to set OnsetSignalData to address  two pins (one
>included in the strobe (parallel port output pins 2-9 (= D0-D7 = &H378
>1-255) and one on parallel port pin 1 (=C0, &H378+2) ? This may sound
>complicated but we have used this approach successfully as a way to
>communicate between systems where the timing was not as critical.
>Hank
>
>On Mar 30, 12:40 pm, Paul Groot <pfc.gr... at gmail.com> wrote:
> > Hi Hank,
> >
> > When using event markers for visual stimuli, you never should use the
> > writeport function. This is because (in most cases) you would like to
> > present the visual stimulus during the short refresh fase of the
> > display. This is the default case when onset sync is set to vertical
> > blank. (As David already explained!) If the stimulus is not synced
> > this way, you will end up with an incomplete first frame (flickering).
> > So, in most cases this causes unpredictable onset delays. Therfore,
> > any writeport call will be executed to early, because eprime will hold
> > the image presentation until the next refresh occurs (=OnsetDelay).
> > So, just use the Onset/Offset properties described in the previous
> > emails. The OnsetSignal will automatically generate a trigger as soon
> > as the image is presented. (I.e. EPrime will automatically sync the
> > implicit writeport command properly)
> >
> > Also: Preparation of  the image (loading, uncompressing, scaling, ...)
> > could be performed during a so called pre-release period. This period
> > can be defined in the object just before the stimulus. This is advised
> > for accurate onset times because image preparation time is NOT fixed
> > in general. However, be carefull if you put any inline script between
> > this object and the stimulus. (It will be executed at the start of the
> > pre-release period!)
> >
> > best
> > paul
> >
> > 2011/3/30 Hank Jedema <Jed... at pitt.edu>:
> >
> >
> >
> >
> >
> >
> >
> > > Thanks to Davis, Baris, and Paul for your quick responses.
> > > I used a writeport command in my code to send my event markers to my
> > > recording system. I will have to look up what the exact loading time
> > > of an image on my Elo Carroll touch screen is, because I did not
> > > adjust for that (fixed) delay yet.
> > > I based my question on the timing of the event markers on the
> > > following: I collect multiple event markers for both the stimulus
> > > appearance as well as the response timing using a electrophysiology
> > > rig with sub-millisecond (<0.15 msec) timing accuracy. When I compare
> > > the time difference between 2 event markers from touch screen
> > > responses it seems that Eprime and my Plexon rig correspond nicely
> > > (<1msec difference). When I compare the time difference between an
> > > event marker from a stimulus appearance and a touch screen response,
> > > there is a much greater difference (10-18msec). On a trial by trial
> > > basis the difference between the two event markers seems to match the
> > > stimulus.onset delay listed in the Eprime output. Based on this, I
> > > believe that the event marker sent out by my E-prime code precedes the
> > > appearance of the stimulus on the screen. I will try the suggestion to
> > > use an inline as soon as the stimulus is on the screen next week. I
> > > will also check on the thread that David provided and post my results.
> >
> > > Best,
> > > Hank
> >
> > > On Mar 30, 2:39 am, Paul Groot <pfc.gr... at gmail.com> wrote:
> > >> 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 <Jed... 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

-- 
You received this message because you are subscribed to the Google Groups "E-Prime" group.
To post to this group, send email to e-prime at googlegroups.com.
To unsubscribe from this group, send email to e-prime+unsubscribe at googlegroups.com.
For more options, visit this group at http://groups.google.com/group/e-prime?hl=en.