Post by thread:DTMF signal generation with PIC, how ?

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}> 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}

>>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"

> 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. :)

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

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

> 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)

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}

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

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 \_ / \___________ .....eriveraKILLspam@spam@umemphis.campus.mci.net

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

> "*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,

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: cousensKILLspamher.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)

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

So does JRC. Craig -----Original Message----- From: Dennis Plunkett <.....dennisKILLspam.....RDD.NECA.NEC.COM.AU> To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU <PICLISTspam_OUTMITVMA.MIT.EDU> Date: Sunday, November 01, 1998 1:06 PM Subject: Re: DTMF signal generation with PIC, how ? {Quote hidden}>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

> 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.