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Yes please, I would like the PIC code. I did
something similar in the past using a 16C71 PIC with 8 bit A/D. This
sampled at 4kHz and formed I/Q samples at 1kHz output rate as follows for every
4 input samples :
I = S1 + S2 - S3 - S4
Q = S1 - S2 - S3 + S4
This is valid PROVIDED the audio is prefiltered to
the range 750 - 1250 Hz only which is the case for most CW filters in
rigs. It worked OK, but Soundcards do a better job, provided someone else
writes teh software for them ;-)
Andy G4JNT
----- Original Message -----
Sent: Wednesday, October 30, 2002 5:23
PM
Subject: Re: LF: sound cards...well amybe
if.....
Hello Group,
If
someone knows an easy way to get started in USB programming, I'd like to try
interfacing one of those PIC's with fast ADC and USB interface to a PC.
(For a dummy like me, who does not really love windoze programming)
What I have done recently is writing a firmware for a PIC12F675 which
sends I/Q samples to the PC through the serial port. The sampling rate is
*exactly* 2500 samples/second, if the PIC is clocked with *exactly* 10.000
MHz. Not really suited for a software defined radio, but good for narrow-band
work, and you can clock it with your high-precision GPS-sync'd source !
If
someone wants to have the assembly sourcecode, or like to connect this simple
converter on his DOS/Windoze/Linux program, please ask. The serial data format
is very simple (4-byte-frames, 115.2kBit/second, 1 start+ 8 data + 1 stopbit,
so data can be received through "COM1" or "COM2" using standard routines. The
PIC12F675 is very cheap (~1.5 Euros), and is available in DIL-8 case. It can
be programmed with one of those "simple PIC programmers" ;-)
Regards,
Wolf DL4YHF.
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