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'DTMF - Telephone Related'
1997\06\11@161822 by jolyal

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Hello,

       I live in Canada and I'm looking for some information on how
I can detect DTMF tones on my telephone line using a PIC. Also, I would
like to know how I can detect the telephone ringing on the tel. line.

       The thing I want to do is when somebody calls, after x number of
ring, the devices takes-up the phone and sends a message. (ex: Hello,
you have reached 777-7777, for the english version, press 1 - To make
blablaba, press 2.....) After, the caller will press number 1 or number
2 (etc) depending on the option he wants to make... Could that be done
easly? Oh yeah, Im using a special analog voice recording IC for the
message....

       Any information, help, links, source code - or should I say, anything
that could help me is greatly appreciated!

       FAX: (819) 775-3661                     Thank you very much!
       EMAIL: spam_OUTjolyalTakeThisOuTspamcapitalnet.com            Jean-Francois Joly

1997\06\11@201718 by Harold Hallikainen

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On Sun, 11 May 1997 16:14:04 -0400 Jean-Francois Joly
<.....jolyalKILLspamspam@spam@capitalnet.com> writes:
>Hello,
>
>        I live in Canada and I'm looking for some information on how
>I can detect DTMF tones on my telephone line using a PIC. Also, I
>would
>like to know how I can detect the telephone ringing on the tel. line.
>
>        The thing I want to do is when somebody calls, after x number
>of
>ring, the devices takes-up the phone and sends a message. (ex: Hello,
>you have reached 777-7777, for the english version, press 1 - To make
>blablaba, press 2.....) After, the caller will press number 1 or
>number
>2 (etc) depending on the option he wants to make... Could that be done
>easly? Oh yeah, Im using a special analog voice recording IC for the
>message....


       I'd be tempted to just use a standard fax/data/voice modem.
These are available for aobut $50 US or less.  It handles interface to
phone line, DTMF generation and detection, and voice transmission and
reception (you send or receive a datastream representing the voice).  I
think this price is kinda hard to beat.  Also, these normally come with
software that will run on a PC.  I'm using SuperVoice Pro and am quite
impressed with it.

Harold

1997\06\12@053224 by Flavio Rizzardi

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Hello there.

>         I live in Canada and I'm looking for some information on how
> I can detect DTMF tones on my telephone line using a PIC. Also, I would
> like to know how I can detect the telephone ringing on the tel. line.

I've just completed a similar project. I used an 8870 from Mitel to decode
the incoming DTMF tones (they have the datasheet online at, I believe,
http://www.mitel.com). It sends out a 4 digit hex code plus strobe to indicate
the last tone detected.
To detect the ring, I simply used an optocoupler (SFH620 or similar)
placed after a 470 nF 250V capacitor, a 10 KOhm resistor and two
back-to-back 24V zener diodes to block everything but the ring.
By the way, if somebody has better ideas, please tell me.

bye,
  Flavio

1997\06\12@082427 by Stephen R. Synakowski

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Harold Hallikainen wrote:
{Quote hidden}

Can I ask how you're detecting the DTMF tones? I'm in the middle of the
same type of project. Are you using a script, or other language, and is
this DTMF reception non-standard for different modems?
Thanks, Steve.

1997\06\12@094344 by Byron A Jeff

face picon face
>
> Hello there.
>
> >         I live in Canada and I'm looking for some information on how
> > I can detect DTMF tones on my telephone line using a PIC. Also, I would
> > like to know how I can detect the telephone ringing on the tel. line.
>
> I've just completed a similar project. I used an 8870 from Mitel to decode
> the incoming DTMF tones (they have the datasheet online at, I believe,
> http://www.mitel.com). It sends out a 4 digit hex code plus strobe to indicate
> the last tone detected.

I presume from your description of the ring detector below that you didn't
use a Data Access Arrangement? Also how did you interface the 8870 to the
phone line?

BAJ
> To detect the ring, I simply used an optocoupler (SFH620 or similar)
> placed after a 470 nF 250V capacitor, a 10 KOhm resistor and two
> back-to-back 24V zener diodes to block everything but the ring.
> By the way, if somebody has better ideas, please tell me.
>
> bye,
>    Flavio
>

1997\06\12@121118 by Harold Hallikainen

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On Thu, 12 Jun 1997 08:23:40 +0000 "Stephen R. Synakowski"
<.....srs1KILLspamspam.....IX.NETCOM.COM> writes:

>> Harold
>Can I ask how you're detecting the DTMF tones? I'm in the middle of
>the
>same type of project. Are you using a script, or other language, and
>is
>this DTMF reception non-standard for different modems?
>Thanks, Steve.
>


       The DTMF tone detection is part of the extended AT command set.
I haven't actually written any code for it, but when I last looked at the
manual on the modem, it looked pretty straightforward.  I've got a couple
using the Cirrus Logic chipset.  There is also a Rockwell chipset that is
common.  Unfortunately, they do not use the same codes.
       Years ago I developed a product that included our own modems for
use on leased lines (using Bell 202 half duplex at 1200 bps).  The modems
were based on the XR2206 and 2211.  They worked well, but if there was
ever ANYTHING a customer could not get to work, it was the modems not
talking to each other due to line impairments.  Since then I've decided
that there are lots of people specializing in modem design, and I didn't
have to do it.  I think that the existence of voice/data/fax modems that
are already FCC approved (and approved for direct connection in outher
countries as well) should be taken advantage of.  Sure we can build our
own DAA, use an opto for ring detection, use a few more chips for DTMF
generation and detection, a few more chips for voice generation.  With a
standard modem card, however, we get the whole thing already done.  If we
want to send fixed voice messages, they could be handled by an EPROM (or
EEPROM or battery backed RAM) sitting outside a PIC.  For simplicity, I'd
probably just set it up as general storage (instead of trying to send the
data directly to the modem card).  The PIC can then pull voice data from
the EPROM and send it to the modem.
       Speaking of RAM expansion...  THANKS to whomever suggested the
Dallas RamPort chips.  I've now got them designed into two products and
will soon start on the third.
       Speaking further of expansion...  What about this stuff of using
a single chip micro, then piling so many other chips around it that we
might as well have just used a standard microprocessor instead of a
microcontroller?  It seems to me that microcontrollers are ideal for
small designs where the vast majority of the functionality is on the
controller.  However, if we have to start using the chip in an "expanded
mode" where most of the I/O that we're paying for ends up being processor
bus, aren't there less expensive ways of getting processor bus?  Also,
asuming size constraints can be met, once we go beyond a certain size,
how about just turning our design into an I/O board for the PC bus and
using low cost motherboards that are already out there?  I did a project
a while back where one of our I/O boards included EPROM sockets so BIOS
would find and load our code instead of trying to boot from disk.  Lotta
power for not much money!


Harold


Harold

1997\06\12@201200 by Ross McKenzie

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At 10:30 AM 6/12/97 +0200, you wrote:
>Hello there.
>
>>         I live in Canada and I'm looking for some information on how
>> I can detect DTMF tones on my telephone line using a PIC. Also, I would
>> like to know how I can detect the telephone ringing on the tel. line.
>
>I've just completed a similar project. I used an 8870 from Mitel to decode
>the incoming DTMF tones (they have the datasheet online at, I believe,
>http://www.mitel.com). It sends out a 4 digit hex code plus strobe to indicate
>the last tone detected.
>To detect the ring, I simply used an optocoupler (SFH620 or similar)
>placed after a 470 nF 250V capacitor, a 10 KOhm resistor and two
>back-to-back 24V zener diodes to block everything but the ring.
>By the way, if somebody has better ideas, please tell me.
>
>bye,
>   Flavio
>

Flavio,

That is certainly a technically acceptable solution. However, here in
Australia, such connections to the telephone network are illegal. Something
to do with possibly killing a telephone worker outside working on the lines
trying to understand why his levels and impedances are out of whack. <g>

Could be worth investigating first.

Regards,

Ross McKenzie
Melbourne Australia

1997\06\12@204112 by John Payson

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>         Speaking further of expansion...  What about this stuff of using
> a single chip micro, then piling so many other chips around it that we
> might as well have just used a standard microprocessor instead of a
> microcontroller?  It seems to me that microcontrollers are ideal for
> small designs where the vast majority of the functionality is on the
> controller.  However, if we have to start using the chip in an "expanded
> mode" where most of the I/O that we're paying for ends up being processor
> bus, aren't there less expensive ways of getting processor bus?

I agree that in many cases where a micro is used to run code out of
external memory, a microprocessor would be just about as effective (esp.
since many UART chips can be set up for periodic timer interrupts, provide
some spare I/O, etc.)  On the other hand, there can be a number of
advantages to running code out of internal memory:

[1] The code can be protected reasonably well from prying eyes.  By
contrast, it's not possible to protect the code in an external EPROM
without rendering it useless.

[2] If the CPU is running code from internal memory and only accessing the
bus occasionally, the bus will radiate less than if the CPU were running
code from it.  In addition, glitches on the bus (or dropped screwdrivers)
are less likely to cause errant behavior.

[3] If there are any problems with a microprocessor's bus (e.g. shorted
lines, open-circuits, etc..) the CPU itself will be running random code
and will not be able to aid in any diagnostics.  By contrast, a program in
the CPU's internal memory may test external memory and indicate faults; it
may also provide other troubleshooting aids (such as outputting a known
continuous sequence of memory accesses).  From my experience, this can be
a great aid to trouble-shooting (since it's possible to simply look at
different spots on the board to see if the proper waveforms appear).

[4] Many systems may normally run code out of RAM or Flash, but need some
way to get it there (or replace it if it gets corrupted).  While
boot-block flash is good for this, it's also possible to use a micro with
a small bootstrap program in ROM.  This may eliminate the need to have an
external EPROM.

There are probably more reasons, but those are a few to start with...

1997\06\12@225759 by Mike Smith

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----------
{Quote hidden}

You forgot to mention when using PC's for embedded apps the fact that
you've got really cheap development environments and C compilers...

MikeS
<@spam@mikesmith_ozKILLspamspamrelaymail.net>

1997\06\13@001308 by Harold Hallikainen

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On Thu, 12 Jun 1997 19:33:38 +0000 John Payson <KILLspamsupercatKILLspamspamMCS.COM> writes:

>[3] If there are any problems with a microprocessor's bus (e.g.
>shorted
>lines, open-circuits, etc..) the CPU itself will be running random
>code
>and will not be able to aid in any diagnostics.  By contrast, a
>program in
>the CPU's internal memory may test external memory and indicate
>faults; it
>may also provide other troubleshooting aids (such as outputting a
>known
>continuous sequence of memory accesses).  From my experience, this can
>be
>a great aid to trouble-shooting (since it's possible to simply look at
>different spots on the board to see if the proper waveforms appear).



       This is ESPECIALLY useful!  Some of the products here do use an
external EPROM with the processor bus brought out to it.  Troubleshooting
a wild processor is a pain!

Harold

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