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PICList Thread
'Telephone modem PIC source code wanted...'
1997\09\28@071756 by Glenn Johansson

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>I've seen a California-designed house alarm with a built-in
>modem/communicator. On closer inspection (opening the damn thing) it
>turned out to be a 16MHz 16C74 doing to whole lot. Quite impressive.

But did it emulate an actual modem or just a DTMF-sender? An alarm just needs to send the touch-tone frequencies as far as I can understand, plus perhaps a digit or two to inform about the alarm type. Unless it's going to broadcast live via an onboard  camera and microphone.

The day someone writes PIC code to emulate a 300 bps or even an 1200 bps bidirectonal modem, and distribute the code public domain, THEN I will be impressed. ;-)

1997\09\28@105356 by Tom Mariner

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> But did it emulate an actual modem or just a DTMF-sender? An alarm just =
> needs to send the touch-tone frequencies as far as I can understand, =
> plus perhaps a digit or two to inform about the alarm type. Unless it's =
> going to broadcast live via an onboard  camera and microphone.
>
> The day someone writes PIC code to emulate a 300 bps or even an 1200 bps =
> bidirectonal modem, and distribute the code public domain, THEN I will =
> be impressed. ;-)

Be impressed - did it 8 years ago on an 8048 at 300 bps for a major alarm
panel manufacturer. One needs bi-directional so the alarm company can modify
parameters from their office.

Tom

1997\09\28@160825 by Eric van Es

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Tom Mariner wrote:

> > But did it emulate an actual modem or just a DTMF-sender? An alarm just =
> > needs to send the touch-tone frequencies as far as I can understand, =
> > plus perhaps a digit or two to inform about the alarm type. Unless it's =
> > going to broadcast live via an onboard  camera and microphone.
> >
> > The day someone writes PIC code to emulate a 300 bps or even an 1200 bps =
> > bidirectonal modem, and distribute the code public domain, THEN I will =
> > be impressed. ;-)
>
> Be impressed - did it 8 years ago on an 8048 at 300 bps for a major alarm
> panel manufacturer. One needs bi-directional so the alarm company can modify
> parameters from their office.
>
> Tom

Same thing with faxmachines - also remotely adjustable. But that won't impress
him - its not public domain! <G>

--
Eric van Es               | Cape Town, South Africa
spam_OUTvanesTakeThisOuTspamilink.nis.za | http://www.nis.za/~vanes
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1997\09\29@011135 by tjaart

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Glenn Johansson wrote:
>
> >I've seen a California-designed house alarm with a built-in
> >modem/communicator. On closer inspection (opening the damn thing) it
> >turned out to be a 16MHz 16C74 doing to whole lot. Quite impressive.
>
> But did it emulate an actual modem or just a DTMF-sender? An alarm just needs
to send the touch-tone frequencies as far as I can understand, plus perhaps a
digit or two to inform about the alarm type. Unless it's going to broadcast
live via an onboard  camera and microphone.
>

I'm not sure. I didn't have it long enough to test all the goodies. :(

> The day someone writes PIC code to emulate a 300 bps or even an 1200 bps
bidirectonal modem, and distribute the code public domain, THEN I will be
impressed. ;-)

Wait for that 50 MIPS Scenix chip. You'd be able to stir you a Martini
and communicate at a few thousand baud...

--
Friendly Regards

Tjaart van der Walt
.....tjaartKILLspamspam@spam@wasp.co.za
_____________________________________________________________
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1997\09\29@040957 by Andrew Warren

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Glenn Johansson <PICLISTspamKILLspamMITVMA.MIT.EDU> wrote:

> > I've seen a California-designed house alarm with a built-in
> > modem/communicator. On closer inspection (opening the damn thing)
> > it turned out to be a 16MHz 16C74 doing to whole lot. Quite
> > impressive.
>
> But did it emulate an actual modem or just a DTMF-sender? An alarm
> just needs to send the touch-tone frequencies as far as I can
> understand, plus perhaps a digit or two to inform about the alarm
> type.

   Glenn:

   Only the very cheapest alarm panels communicate via DTMF
   tones... All the "real" ones use various (incompatible) FSK
   schemes to communicate with the central station.

   Most central stations don't use Bell 103 (the 300 baud modem
   standard), so very few panels perform the communication using
   off-the-shelf modem chips... In nearly all cases, the
   (bidirectional) communication is handled in software, usually
   using a resistor ladder to do the outgoing D/A conversion.  FSK
   reception is generally handled completely in software by timing
   zero-crossings of the incoming signal.

> The day someone writes PIC code to emulate a 300 bps or even an 1200
> bps bidirectonal modem, and distribute the code public domain, THEN
> I will be impressed. ;-)

   It's not that hard... In a previous life, I was employed by an
   alarm company that did a VERY comprehensive communicator using a
   6805 running at 4 MHz.  I think it was first released in, like,
   1982.

   Of course, that communicator was half-duplex and didn't need to
   understand the Hayes "AT" modem command set... Adding "AT"
   compatibility and making it full-duplex might be a little
   difficult, especially if you wanted to use one of the smaller
   PICs like the 16C54.

   -Andy

=== Meet other PICLIST members at the Embedded Systems Conference:
=== 6:30 pm on Wednesday, 1 October, at Bytecraft Limited's booth.
===
=== For more information on the Embedded Systems Conference,
=== see: http://www.embedsyscon.com/

=== Andrew Warren - .....fastfwdKILLspamspam.....ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499

1997\09\29@111218 by Martin R. Green

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Nor was it done with a PIC!

CIAO - Martin R. Green
EraseMEelimarspam_OUTspamTakeThisOuTbigfoot.com

----------
From:   Eric van Es[SMTP:vanesspamspam_OUTILINK.NIS.ZA]
Sent:   Sunday, September 28, 1997 3:55 PM
To:     @spam@PICLISTKILLspamspammitvma.mit.edu
Subject:        Re: Telephone modem PIC source code wanted...

Tom Mariner wrote:

{Quote hidden}

Same thing with faxmachines - also remotely adjustable. But that won't impress
him - its not public domain! <G>

--
Eric van Es               | Cape Town, South Africa
KILLspamvanesKILLspamspamilink.nis.za | http://www.nis.za/~vanes
LOOKING FOR TEMPORARY / HOLIDAY ACCOMODATION?
http://www.nis.za/~vanes/accom.htm

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