parallel port communications

[Mary K. Colvin]

Hello,

I am wondering if anyone has any tips on using the port device to
receive input from an external device via the parallel port.  My goal is
to record subjects' reaction times to a SoundOut stimulus using two
external buttons/switches (unfortunately I can't use a button box for
this design).  Currently, I've got a button/switch with an external 5V
supply going across a resistor that has a ground line into the parallel
port and an input line into the parallel port.  My first question is to
what pin should I connect the input line?  From the instructions on
E-Prime's website, I assume that the input needs to come in on the
status register pins (10, 11, 12, 13, 15).  I have tried connecting to
each of these pins and none of them works from within E-Prime.  I'm
pretty sure I've got the right port address and that it works - I've
written an InLine object that uses the WritePort command to send TTL
pulses to the data register pins on the same port (address is 278) and
measured the TTL pulses using a voltmeter.  I'm also pretty
sure that the switch works because I've used a monitoring program
outside of E-Prime to observe that when I press the button and the input
line is on pin 15, pin 15's status goes from high to low.  I have set the port input
device address to the status register address (279).  So I can't figure out why E-Prime isn't recording a response when I run the same set-up from within E-Prime.  Help?

My second question is whether I can differentially receive input from
two external devices through the same parallel port.  In other words, if
I can get E-Prime to recognize one external switch through the parallel
port, will it be able to differentially recognize a second switch
through the same parallel port, or will I need another parallel port?
My goal here is to be able to tell not only how fast the subjects were,
but which button/switch they pressed.  Is the port device is capable of
reading individual input pins?  If so, how do I specify it?  Would I
change the bit number?

Thanks in advance for any comments, help, and advice.
Molly Colvin

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Molly Colvin 
Department of Psychological and Brain Sciences
Dartmouth College
6207 Moore Hall
Hanover NH 03755