PC-based MIDI-CV Converter - Part 2

johns at oei.com johns at oei.com
Mon Mar 25 18:58:02 CET 1996

     Several years ago I used a PC printer port to control a speech chip in 
     much the same way Gene did.  I would like to warn you all of a problem 
     that I had to fix in my project...
     It seems that my old 286 that I got in 1986 used one of those old XT 
     "Multifunction" cards (2 parallel, 2 serial, one timer, and room for 
     384K memory).  This card had .01 uF damping caps on all the data lines 
     and some of the control lines that I had to cut out.  I don't know if 
     these caps are standard equipment on parallel port cards but it caused 
     a problem because they got in the way of the setup time needed by the 
     latch when I quickly multiplexed 4 bits of data to 8 bits.  I think a 
     normal Centronics printer port has a handshake bit that ensures this 
     is not a problem.  So my using the port without a handshake made it a 
     problem for me.
     Since this MIDI-CV project uses old stuff, please be aware of the 
     problems I had with my old stuff.
     John Speth - johns at oei.com

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