[TRLog] sbdvp II

Kenneth Earl Harker kharker@cs.utexas.edu
Mon, 20 Apr 1998 23:39:35 -0500 (CDT)

     OK, I'm getting frustrated with the SBDVP cabling job I'm trying.

     I have a 486 running DOS 6.2, 16MB RAM, SoundBlaster 16, and IDE CD-ROM 
drive - nothing fancy, nothing exotic.  The sbdvp 1.0.1 TSR seems to load and 
unload fine business.  I'm using the command line 'sbdvp -p1 -o5p1'.  My 
LOGCFG.DAT file includes DVP ENABLE = TRUE and PTT ENABLE = TRUE.  This is 
where we start getting into my limited experience.

     When I hit ctrl-F1, there's a line that shows up in the middle of the 
screen that says something to the effect of "Now recording CQF1.DVP.  Hit
ESC or RETURN to stop."  Should anything else happen at this point?  If 
I press PTT and speak into the mic, release PTT and hit ESC (at which 
point the the aforementioned line of text goes away,) is that all there is
to it, or should I be seeing some other visual cue on the screen as it records?
When I unload the sbdvp TSR, a non-zero-length file CQF1.DVP is written to
disk; is there some way I can play this file in another application to see if
I recorded succesfully?

     My main problem, of course, is playback.  As far as I can tell, hitting
F1 after having recorded via ctrl-F1 as above isn't doing anything on my 
system.  There's no change to pins 1 or 16 on the first printer port (both
seem to always be +5VDC.)  There is no visual indication on screen that 
anything is happening either, and there's no audio going to the line out, 
unless it's static that sounds indistinguishable from no audio. I've wired up 
the PTT line as per the TR Log 6.16 manual, using a genuine 2N2222A.   I've 
checked and rechecked and double rechecked against accidentally crossed wires. 
Can anyone think of something seemingly obvious that I might not be doing?  It 
seems like the PTT circuit at least ought to work right, even if the rest of 
my cabling is jumbled.  Is anyone else using sbdvp with the parallel port PTT?

     Once I get PTT to work, I still need to make sure the microphone mic
element is taken out of line as the soundblaster audio is sent on its merry
way to the radio.  I've wired up something based on a 2N2222A using pin 5
of the parallel port that is supposed to be raised during transmit, but I'm
not sure if I've got it right.  Does anyone have a handy online reference 
for this or could quickly describe the circuit I need?  Let me describe this

     There are two long cables, one of which terminates in a male mic connector
that plugs into the radio and the other terminates in a female mic connector
that the microphone plugs into.  My thought is: connect the mic audio and mic 
ground lines of both cables to each other and the left channel channel of the 
soudblaster line out.  This way, the microphone behaves as you expect, and 
the soundblaster output can go to the radio as well.  Problem - when the 
Soundblaster does this, the microphone element will modulate the room noise,
whatever it may be, and this also gets fed into radio along with the .dvp
audio.  Goal: use a raised signal on pin 5 of the parallel port to a transistor
circuit to cause the mic audio line going to the microphone (which is normally
a closed path) to open, leaving the mic audio and mic ground lines from the 
soundblaster line out to the radio unaffected.  

     If I can get this working, I'll document my cabling job so others
need not struggle with this as much as I have.

     Unfortunately, it doesn't look like I'll get this working in time for
the 222MHz Sprint tomorrow night.

Kenneth E. Harker      "Vox Clamantis in Deserto"      kharker@cs.utexas.edu
University of Texas at Austin                  Amateur Radio Callsign: KM5FA
Department of the Computer Sciences         President, UT Amateur Radio Club
Taylor Hall TAY 2.124               Maintainer of the Linux Laptop Home Page
Austin, TX 78712-1188 USA            http://www.cs.utexas.edu/users/kharker/

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