Embedded FSK MODEM

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I am interested in embedding a 1200 baud modem into a product, using
software.  Something similar to the TDK 73M2901, but rolling my own.  This
thing dials in once a night and does about 3-4 50-byte transactions then
hangs up.  The client wants to do it without a proprietary chip because he's
afraid it'll go EOL.

I'm looking at feasibility.  I have an 8-bit CODEC and a telco POTS line
interface, and an H8S microprocessor.

Has this been done before, and if so, is there software reference source
code out there?



Re: Embedded FSK MODEM
On Sun, 07 Sep 2003 14:52:47 GMT, "Ian McBride"

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Then what are you going to do when the H8S or the CODEC is EOL'd? No
matter what you do, there will be chips that disappear, so why make it
more difficult (and expensive) than necessary. There are several tone
generators around that can send FSK, and PLL's that can receive it. We
used to use the NE555 and 567, or a pair of EXAR chips. Last time I
looked, there were also a couple of off the shelf modem chips that
could do Bell 212 and/or 202.

Bob McConnell
N2SPP


Re: Embedded FSK MODEM
Check out
http://www.cypressmicro.com/Reference%20Designs/ModemDesignIP.pdf
at
http://www.cypressmicro.com/Reference%20Designs/psocreferencedesigns.htm

R.R.
www.orlin.com


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he's



Re: Embedded FSK MODEM
There is a TI application note on implementing an FSK modem on
an MSP430 series processor. You'll have to look carefully to find it.
Another possibility is to do your own modulator for Bell 202 and
use a caller-id chip for the demod. Look at Analog Devices for
some app notes as well.

There is lots of reference material out there.

In terms of MIPS, an ordinary 8051 won't hack it. A small
PIC just manages to do a modulator. AFAIR, 1-2 MIPS is
needed for mod and another 3-4 MIPS is needed for demod.

regards,
Darcy ROberts

Ian McBride wrote:
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