Digital I/O between EPrime and Biopac

[David McFarlane]

At 10/29/2008 06:50 PM Wednesday, Cate wrote:
>I have now gotten Writeport (888,x) to work but I am still unable to 
>read from port 889 (I get a value of 120 regardless of the TTL input 
>I'm sending).  This leads me to believe that I either need to 
>include some code to enable using the port for input, or that my 
>port is not correctly configured in the BIOS for input.  I checked 
>the BIOS and it is currently set to ECP mode.  Other options 
>available for selection are EPP and PS/2.  Would you recommend using 
>a different mode?

Would not hurt.  ECP and EPP are newer "bidirectional" parallel port 
modes, PS/2 is the original, standard, "legacy" parallel port 
mode.  I would try the PS/2 mode first.  After that fails I would try 
the EPP mode for good measure.  After that fails I would follow the 
link I sent earlier and try following those instructions.  Don't know 
what I would do after that fails.

Before all that I would put a volt meter or oscilloscope on the 
parallel port inputs to make sure they are what I think they are.  I 
might also disconnect the BioPac and use another known signal 
source.  I might also look at the output from the BioPac to make sure 
that that is what I think it is.  Finally, I might find some other 
more primitive software to inspect the state of the parallel port.  I 
used to do this with the "i" command from the old DOS "debug" 
utility, I don't know if that still works with modern Windows.  Short 
of that I would write a primitive E-Prime script to just continually 
display the state of the parallel port (and maybe a few neighboring 
ports for good measure), just to make my debugging a little easier.

-- David McFarlane, Professional Faultfinder


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