parallel port communication: event markers

[David McFarlane]

Sofia,

> I changed the content of the Inline and now I only have one Inline
> after the Proposal with the following:
> 
> If Proposal.RESP = "a" then WritePort &H378, Asc(Proposal.Resp) else
> if Proposal.RESP = "r" then WritePort &H378, Asc(Proposal.Resp) else
> WritePort &H378, 255
> 
> Sleep 20
> WritePort &H378, 0
> 
> Is this what you're suggesting?

Good job!  If you have this working then you do not need to change a 
thing.  But I will add a short programming lesson.

Your script above has a bit of redundancy.  Here is a way to write it 
without the redundancy (and using constants to get rid of the "magic 
numbers", which I believe improves readability, and adding a few 
comments for clarity):

Const LptDataPort as Integer = &H378  ' or 888 decimal
Const NoResponseEvent as Integer = &HFF  ' or 255 decimal
Const EventPulseDuration_ms as Integer = 20

' Send appropriate event pulse to PsychLab equipment...
If Proposal.RESP <> "" Then  ' got a response
     WritePort LptDataPort, Asc(Proposal.Resp)
Else  ' no response
     WritePort LptDataPort, NoResponseEvent
End If
Sleep EventPulseDuration_ms
WritePort LptDataPort, 0


BTW, you can also test for a response by using

If Proposal.RT <> 0

as well as other tests that I have documented elsewhere.  It is largely 
a matter of personal taste (I like the test against 0, since it seems 
more efficient to test the value of an integer rather than a full string).

-- David McFarlane, Professional Faultfinder


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