<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
DL4YHF@aol.com wrote:
<blockquote TYPE=CITE><font face="arial,helvetica"><font size=-1>Hi all,</font></font>
<p><font face="arial,helvetica"><font size=-1>During a nice QSO in Jason
mode today, and thinking about this and that, a crazy idea went through
my brain. Maybe it's only good for the waste bin but how about this:</font></font>
<p><font face="arial,helvetica"><font size=-1>Let the PC produce a digital
control word for a DDS VIA THE SOUNDCARD ?</font></font>
<p><font face="arial,helvetica"><font size=-1>A DDS like the AD9832 needs
a special serial control word, which is generated by a PIC processor in
most cases. Three digital lines are required. How about "producing" the
control word for the DDS via the SOUNDCARD ? We could either use a stereo
output for clock+data (producing digital signals) , a few clamping diodes,
two or three transistors and possibly a monoflop for the FSYNC signal (a
third control line from PC to PIC). An alternative would be using different
levels for the FSYNC, but proper level adjustment and clamping would be
required because most audio outputs are only "AC coupled".</font></font>
<p><font face="arial,helvetica"><font size=-1>Johan (SM6LKM) has written
a routine in "C" for PIC controllers which I have adapted to run under
DOS, using the parallel port. But it's complicated to do this under windoze,
especially if the DDS shall be controlled in a highly "synchronous" way
through the parallel port.</font></font>
<br>
<p><font face="arial,helvetica"><font size=-1>What would be the benefit
of using the soundcard to drive a DDS ?</font></font>
<br><font face="arial,helvetica"><font size=-1>- you wouldn't need a programmed
PIC processor acting as an interface between PC and DDS.</font></font>
<br><font face="arial,helvetica"><font size=-1>- you wouldn't need a LPT
interface which is tricky to access under Windoze NT + XP.</font></font>
<br><font face="arial,helvetica"><font size=-1>- you wouldn't need a serial
interface which does not exist on some cheap notebooks.</font></font>
<br><font face="arial,helvetica"><font size=-1>- no need to fool around
with USB programming</font></font>
<br><font face="arial,helvetica"><font size=-1>- The serial control word
for the DDS chip can be timed very precisely under windoze. A</font></font>
<br><font face="arial,helvetica"><font size=-1>continuous output (with
update the DDS every 100 ms or so) is possible.</font></font>
<br>
<p><font face="arial,helvetica"><font size=-1>Disadvantages:</font></font>
<br><font face="arial,helvetica"><font size=-1>- It's not a 'stand-alone'
solution. A PC (or at least one of these tiny PDA's) is always needed.
But which of the "modern modes" runs without a PC ?</font></font>
<br><font face="arial,helvetica"><font size=-1>- To implement this, basic
knowledge of Windoze API programming is required. But I know at least one
other reader of this reflector who has.. ;-)</font></font>
<br>
<p><font face="arial,helvetica"><font size=-1>If this sounds interesting,
let me know and I'll do some more "research". The result could be a routine
which produces raw 16-bit analogue samples to drive an AD9832 (which is
the only DDS I have at the moment).</font></font>
<p><font face="arial,helvetica"><font size=-1>73,</font></font>
<br><font face="arial,helvetica"><font size=-1> Wolf DL4YHF.</font></font></blockquote>
<br>
<br> </html>