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'DTMF signal generation with PIC, how ?'
1998\10\30@034726 by Bart Stofferis

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Hi there,

I am wondering who has already experiences with DTMF generation on a
PIC.

Thanks in advance !

good weekend ...

Bart

1998\10\30@064657 by Robert M. Piper

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Bart,

I am getting ready to start a project using a M-8888 DTMF telephone
interface chip. I am using a PIC16C54 to interface with it

Bart Stofferis wrote:

{Quote hidden}

1998\10\30@064910 by Bart Stofferis

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Really ??

I am wondering how you do that !!!

Do you use discrete waveform generation or lookup tables ??

How easier how better !

PS: thanks for your answer !

Bart

> {Original Message removed}

1998\10\30@065735 by Robert M. Piper

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I have not gotten into it that deep yet. I have a book "Microcontroller
Handbook for beginners" that I am taking the project from. I believe that it
uses a table lookup. I found the book at BARNES & NOBLE it was only $10 or
$15. I should be pretty heavy into this project by the end of next week. I
can tell you more then

Bart Stofferis wrote:

{Quote hidden}

> > {Original Message removed}

1998\10\30@070604 by Bart Stofferis

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OK Robert,

good luck this week and send me a mail when you are finished !

In the mean time i try something with discrete sine generation on the
16C73A

have a nice weekend,

Bart (Belgium)

1998\10\30@071853 by Bob Carter

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Check out Teltone. They have several low cost DTMF transmitter, receiver,
and transceiver chips that interface to the PIC very nicely.

Thank You,

Bob Carter, design engineer

Wildlife Materials, Inc.
1031 Autumn Ridge Road
Carbondale, IL 62901, USA

voice (618) 549-6330 (ext. 225)
fax   (618) 457-3340
email spam_OUTwolftechTakeThisOuTspammidwest.net
www   http://www.wildlifematerials.com

1998\10\30@072059 by Bart Stofferis

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       thanks Bob

1998\10\30@121725 by Eduardo R.

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>>Really ??
>>I am wondering how you do that !!!
>>Do you use discrete waveform generation or lookup tables ??
>>How easier how better !
>

BSI and BSII Stamps from parallax are PIC based chips (16c56-16c57). They
generate DTFM signals using a simlpe instruction (PBasic) without additional
ICs or special telephone chips associated to the hardware.

DTMFOUT 3,300,200,[6,5,4,2,0,3,0]

First number = pin,next two numbers are milliseconds for each digit and
quiet time between digits. In this case the number to be dialed is 654 20 30.
Is a matter of software I guess.

BTW ,in order to generate DTMF ,is  easy to get the program or is better to
interface special telephone chips to the PIC?

Any idea,please let us know

Eduardo R.

"Happy of those who fears the Lord"

1998\10\30@150045 by Dave VanHorn

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>  BSI and BSII Stamps from parallax are PIC based chips (16c56-16c57). They
> generate DTFM signals using a simlpe instruction (PBasic) without additional
> ICs or special telephone chips associated to the hardware.
>
>  DTMFOUT 3,300,200,[6,5,4,2,0,3,0]


That's nice, but do they give you a reccomended filter to achieve the
spectral purity required by the FCC??

DTMF chips still require filtering, but are a lot easier to get there
with.

If your app dosen't involve connection to phone lines, then all you need
to worry about is if the detector will respond properly to your sqawk.
:)

1998\10\30@151123 by Peter L. Peres

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On Fri, 30 Oct 1998, Eduardo R. wrote:

>  BTW ,in order to generate DTMF ,is  easy to get the program or is better to
> interface special telephone chips to the PIC?

There is no 'better'. If you need it yesterday, use a M58?? DTMF generator
which interfaces to the PIC on a 4 bit + strobe bus. If you like to write
your own code (and make more money ;) look into sinus generation using
quarter sinus stored tables for a resolution of 6 bits or so. You need to
generate two waves of different frequencies at the same time, add the
results and output them to an A/D with less than 5% distorsion, or
thereabouts. This is a pretty hectic activity for a PIC and it can do
nothing else meanwhile so consider this too when choosing.

I think that there is a Microchip AN dealing with this and Scott Dattalo
has some information on his home page.

Peter

1998\10\30@152346 by Peter L. Peres

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On Fri, 30 Oct 1998, Dave VanHorn wrote:

> >  BSI and BSII Stamps from parallax are PIC based chips (16c56-16c57). They
> > generate DTFM signals using a simlpe instruction (PBasic) without additional
> > ICs or special telephone chips associated to the hardware.
> >
> >  DTMFOUT 3,300,200,[6,5,4,2,0,3,0]
>
>
> That's nice, but do they give you a reccomended filter to achieve the
> spectral purity required by the FCC??
>
> DTMF chips still require filtering, but are a lot easier to get there
> with.
>
> If your app dosen't involve connection to phone lines, then all you need
> to worry about is if the detector will respond properly to your sqawk.
> :)

Even if it does go over phone lines, the spectral problem can be blamed on
the poor line quality ;) Of course not for a production project !

I don't remember any kind of filtering used on MSM DTMF generators. It
just supplies audio into the voice circuit through a RC ?!

Peter

1998\10\30@154230 by Dave VanHorn

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> I don't remember any kind of filtering used on MSM DTMF generators. It
> just supplies audio into the voice circuit through a RC ?!
>
> Peter


I don't remember the numbers, but there is a min attenuation for the
harmonics.
The synth chips shine here, because they usually run 16 "steps" or more
on the output, so the first harmonics with any energy are way out there.
I know we had to at least add an RC to them to get it in spec, and that
was measured on the line. (including transformer and the effects of the
rest of the DAA)

1998\10\30@162014 by David Blain

picon face
If you are looking for a software solution, you can get the complete code
from Scenix. http://www.scenix.com/virtual/vp/index.html

They have a "DTMF Generation" Virtual Peripheral for there SX line (Pic
compatible).  It may take a little time to convert from the parallax syntax
and to adjust the timing to run on a slower device, ( it was written for
50Mhz with interrupts), but at least it wouldn't be from scratch.

They also include a app note .PDF file with a simple RC Filter circuit
needed for the device.

Just something I ran across and thought it might be helpful.

David.


{Original Message removed}

1998\10\30@164449 by Scott Dattalo

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Peter L. Peres wrote:
>
> On Fri, 30 Oct 1998, Eduardo R. wrote:
>
> >  BTW ,in order to generate DTMF ,is  easy to get the program or is better to
> > interface special telephone chips to the PIC?
>
> There is no 'better'. If you need it yesterday, use a M58?? DTMF generator
> which interfaces to the PIC on a 4 bit + strobe bus. If you like to write
> your own code (and make more money ;) look into sinus generation using
> quarter sinus stored tables for a resolution of 6 bits or so. You need to
> generate two waves of different frequencies at the same time, add the
> results and output them to an A/D with less than 5% distorsion, or
> thereabouts. This is a pretty hectic activity for a PIC and it can do
> nothing else meanwhile so consider this too when choosing.
>
> I think that there is a Microchip AN dealing with this and Scott Dattalo
> has some information on his home page.


I've got the building blocks, but Eric Smith has the solution:

http://www.brouhaha.com/~eric/pic/dtmf.html


Scott

1998\10\30@165739 by Eduardo R.

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At 02:58 PM 10/30/98 -0500, you wrote:
>>  BSI and BSII Stamps from parallax are PIC based chips (16c56-16c57). They
>> generate DTFM signals using a simlpe instruction (PBasic) without additional
>> ICs or special telephone chips associated to the hardware.
>>
>>  DTMFOUT 3,300,200,[6,5,4,2,0,3,0]
>
>
>>That's nice, but do they give you a reccomended filter to achieve the
>>spectral purity required by the FCC??
>
I think so,...
"*Commercial* designs that interface electronic devices to the phone line
normally require the approval of the  Federal Communications
Commission(FCC)to ensure the quality and reliability of telephone service.
Manufacteres of phone accesories often take the shorcut of using an
offf-the-shelf interface,known a a Data Access Arrangement (DAA).
Since the DAA has already been checked out by the FCC ,it's generally much
easier to get a DAA-based design approved than a from-scratch circuit.
Unfortunately,DAA tend to be somewhat expensive in small
quantities($25+each),and are sold primarily through high-volume
distributors geared toward serving manufacturers."
Following that ,they present a circuit for *experimenters*,*hobbyists*.
It's not full DAA suitable for *production* designs,but good for
*prototyping* DTFM apps.
It is based on a circuit presented in Encyclopedia of Electronic
Circuits,Volume 5,by Graf and Sheets(Mc.GrawHill,1995;ISBN
0-07-011077-8).They give the specific component values and sources and has
been tested.
Application Notes page 359 BSII

>
>>If your app dosen't involve connection to phone lines, then all you need
>>to worry about is if the detector will respond properly to your sqawk.
>:)

Of course I'm connecting to the phone line and all the hardware is easy to
find even at any garage sale (answering machines and phones for about 5
bucks). My worry is not the hardware but the software for the PIC because
each Basic StampII costs $49 or $25 the single PIC 16c57 programmed(ready
for PBasic instructions).

Hope this give you an answer.

"The LORD is my rock, my shield."
" Happy of those who fears The Lord "
                    Humbleness is the clue.
         ________  ________  ________
        /         /       / /       /
       /_____    /_______/ /_______/
      /         /  \      / \
     /________ /    \    /   \
     ICQ# 10909825   \_ /     \___________
     .....eriveraKILLspamspam@spam@umemphis.campus.mci.net

1998\10\30@190702 by Regulus Berdin

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Hello,

Try this:

;**********************************************************************
;DTMF GENERATION
; by Regulus Berdin
; W holds the key to send
; 10-A  11-B  12-C  13-D  14-*  15-#
; uses 18 cycles per count optimized for 4MHz crystal
;
;DTMF                           ERROR
;TONE   DELAY   TONE GENERATED  (Hx)    %
;697    40      694.4444444     2.56    0.37
;770    36      771.6049383     1.60    0.21
;852    33      841.7508418     10.25   1.20
;941    30      925.9259259     15.07   1.60
;1209   23      1207.729469     1.27    0.11
;1336   21      1322.751323     13.25   0.99
;1477   19      1461.988304     15.01   1.02
;1633   17      1633.986928     0.99    0.06

       cblock  LASTVAR
               lowcnt
               highcnt
               slowcnt
               shighcnt
               hdcnt
               ldcnt
       endc

tlowcnt
       addwf   PCL,f
       dt      30, 40, 40, 40
       dt      36, 36, 36, 33
       dt      33, 33, 40, 36
       dt      33, 30, 30, 30

thighcnt
       addwf   PCL,f
       dt      21, 23, 21, 19
       dt      23, 21, 19, 23
       dt      21, 19, 17, 17
       dt      17, 17, 23, 19

dtmfsend:
       andlw   0x0f
       movwf   tmp
       call    tlowcnt
       movwf   slowcnt
       movwf   lowcnt

       movf    tmp,w
       call    thighcnt
       movwf   shighcnt
       movwf   highcnt

       clrf    ldcnt
;       movlw   .22                     ;adjust here for delay
       movlw   MTXLENGTH
       call    EE_read
       addlw   1
       movwf   hdcnt                   ;approx. 100 ms

dloop0  clrwdt                          ;2
       nop                             ;
dloop   movlw   (DHI_PIN + DLOW_PIN)
       decfsz  lowcnt,f
        andlw  DHI_PIN
       decfsz  highcnt,f
        andlw  DLOW_PIN
       movwf   tmp
       xorwf   PORTB,f

       movf    slowcnt,w
       btfsc   tmp,0
        movwf  lowcnt

       movf    shighcnt,w
       btfsc   tmp,1
        movwf  highcnt                 ;13

       IF      DTMFTESTING
       nop
       goto    dloop0
       ENDIF

       decfsz  ldcnt,f                 ;2/1
        goto   dloop0                  ;2
       decfsz  hdcnt,f                 ;2/1
        goto   dloop                   ;2      ;5

       return

This routine uses 2 pic pins for high and low tones.  Just add 2 stage
low pass filters the each of the pins and combine both.  This works well
and has a low error less than dtmf receiver specs.

Reggie

1998\10\30@201140 by Dave VanHorn

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>  "*Commercial* designs that interface electronic devices to the phone line
> normally require the approval of the  Federal Communications
> Commission(FCC)to ensure the quality and reliability of telephone service.

You're preaching to the choir on that one, I designed modems into US and
other countries for several years.

>  Following that ,they present a circuit for *experimenters*,*hobbyists*.
> It's not full DAA suitable for *production* designs,but good for
> *prototyping* DTFM apps.

Halfway.. Those "experimenter" circuits shouldn't really be connected to
the PSTN. Half of it is technical, in that joe experimenter could cause
problems for the central office, his neighbors, or who knows what. The
other half is safety, in that the DAA protects the experimenter from
line faults that can take the phone line to 120VAC or more, and it also
protects the phone system from the same thing in the other direction.

You can make a telco line simulator that's fairly good without spending
a lot of money.. When I was doing it, I never connected anything to real
lines until we had passed part 68 with it. We specifically bought Analog
Mitel PBX systems because their inside lines were almost exactly
identical to POTS lines.

>  Of course I'm connecting to the phone line and all the hardware is easy to
> find even at any garage sale (answering machines and phones for about 5
> bucks). My worry is not the hardware but the software for the PIC because
> each Basic StampII costs $49 or $25 the single PIC 16c57 programmed(ready
> for PBasic instructions).

I've done it (DTMF generation) in a Z8, with a pair of 4 bit R/2R D/A
converters, made with resistors off the chip pins. It chews a lot of
pins though, and you'll need 1% resistors to get any purity at all.  1/4
of a sine wave in a table, up, down, backwards and forwards, at two
different rates, marching to the beat of a single timer int.
(Simultaneously decoding EAN-13 barcodes on the fly from a hand-scanned
lightpen) It took a 12.288 Mhz clock to get there. The pic should do
better, since it's got more instrs per clock. OTOH, the Z8 had 192
registers, any one can be used for anything.

It's workable,

1998\10\31@090848 by cousens

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Eduardo R. wrote:

SNIP

>  My worry is not the hardware but the software for the PIC because
> each Basic StampII costs $49 or $25 the single PIC 16c57 programmed(ready
> for PBasic instructions).

Is Parallax still hiding the fact they sell basic stamp2 chips for
$25 in quantitys of ones, and $20 in quantitys of 5

Peter Cousens
email: cousensspamKILLspamher.forthnet.gr  phone: + 3081 380534
snailmail:  Folia, Agia Fotini, Karteros, Heraklion  Crete, Greece.

Is it true that they have, on the new version of windows
managed to increase the MTBF from 95 to 98 minutes ?
(That's why they called it 95)


'DTMF signal generation with PIC, how ?'
1998\11\01@160412 by Dennis Plunkett
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At 13:04 30/10/98 +0100, you wrote:
>OK Robert,
>
>good luck this week and send me a mail when you are finished !
>
>In the mean time i try something with discrete sine generation on the
>16C73A
>
>have a nice weekend,
>
>Bart (Belgium)
>
>



Due to the level, and THD limits required for DTMF (0.5% in Australia), yet
alone the inter-digit timing requirements (75mS) etc. I would recommend that
you use a chip to do it, Mitel (TM) make some that most people are used to.
Others like Samsung, Toshiba and NEC (All TM) are also made and exist,
however I think that only Mitel make a Transceiver.

Dennis

1998\11\01@181547 by Craig Lee

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So does JRC.

Craig

-----Original Message-----
From: Dennis Plunkett <.....dennisKILLspamspam.....RDD.NECA.NEC.COM.AU>
To: EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU <PICLISTspamspam_OUTMITVMA.MIT.EDU>
Date: Sunday, November 01, 1998 1:06 PM
Subject: Re: DTMF signal generation with PIC, how ?


{Quote hidden}

that
>you use a chip to do it, Mitel (TM) make some that most people are used to.
>Others like Samsung, Toshiba and NEC (All TM) are also made and exist,
>however I think that only Mitel make a Transceiver.
>
>Dennis

1998\11\01@232028 by Dave VanHorn

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> Due to the level, and THD limits required for DTMF (0.5% in Australia), yet
> alone the inter-digit timing requirements (75mS) etc. I would recommend that
> you use a chip to do it, Mitel (TM) make some that most people are used to.
> Others like Samsung, Toshiba and NEC (All TM) are also made and exist,
> however I think that only Mitel make a Transceiver.
>
> Dennis


75T2091 from TCS? The number's right, but I forget the Mfgr. They have
four slightly different transcievers.

1998\11\02@155135 by paulb

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Craig Lee wrote:

> So does JRC.

 Pity they don't have a website with PDF specs.
--
 Cheers,
       Paul B.

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