jh@mit-amt.MEDIA.MIT.EDU (John Underkoffler) (07/17/87)
Does anyone know who (if anybody) is making DTMF decoder chips? Neither the TI nor the Motorola "Communications Databooks" as recently as 1985 shows that any such chip exists (although there are plenty of DTMF encoder chips available). Ideally, I'd want a chip which accepts an analog input and produces either a digital hex output (in the range 0-15)or a "row and column" output indicating the position of the button on the imagined phone from which the signal came. The point of all this is that I'd like to selectively activate one of sixteen (or twelve, or whatever) devices by radio remote control, and it seemed to me that one of the easiest ways to realize this would be to follow the phone company's lead and transmit voice-frequency DTMF tones (via disemboweled walkie-talkie); each target unit could then be constantly receiving the same radio frequency transmission; simple logic stuff inside the unit would then read the output of the local DTMF decoder chip and decide if it should activate the associated mechanism. Comments? Ideas? Insults? John "Wombat Stomper" Underkoffler alias "jh@media-lab.media.mit.edu"
larry@kitty.UUCP (Larry Lippman) (07/18/87)
In article <1377@mit-amt.MEDIA.MIT.EDU>, jh@mit-amt.MEDIA.MIT.EDU (John Underkoffler) writes: > Does anyone know who (if anybody) is making DTMF decoder > chips? Neither the TI nor the Motorola "Communications Databooks" as > recently as 1985 shows that any such chip exists (although there are > plenty of DTMF encoder chips available). Ideally, I'd want a chip > which accepts an analog input and produces either a digital hex output > (in the range 0-15)or a "row and column" output indicating the > position of the button on the imagined phone from which the signal > came. Try using Silicon Systems Inc. products such as their SSI201, SSI202, SSI203 or SSI204. These products all take an analog input and provide a BCD digit output. They all use 3.58 color burst crystals for the reference frequency. I have had good luck with SSI products. Or you can try Mitel products such as their MT8862 and MT8865 (used together, the former is the decoder and the latter is a filter), or the integrated MT8870A. The Mitel devices are better quality, but also cost more money. In my opinion, you would be MUCH better off with the above devices rather than attempting to build a discrete DTMF decoder using, say 567 PLL tone detectors. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rocksanne|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
rpluth@pnet01.CTS.COM (Ron Pluth) (07/18/87)
You can pick up a simple DTMF decoder chip at Radio Shack for $10.95. It outputs in straight binary for either the normal 12 digits or for all 16. I think it might also output in some other format, like Gray code, or something. It takes, as has been mentioned, a cheap crystal, and I think it takes straigt audio inputs. Of course, you must be careful in interfacing it directly to a telephone line, as ring voltages run up to ~150 VAC. Ron Pluth UUCP: {akgua, hplabs!hp-sdd, sdcsvax, nosc} | "We are all in the gutter, !crash!pnet01!rpluth | but some of us are looking ARPA: crash!pnet01!rpluth@nosc.mil | at the stars." INET: rpluth@pnet01.CTS.COM | -Oscar Wilde USPS: 13704 Celestial Rd. Poway, CA 92064 |
ron@topaz.rutgers.edu (Ron Natalie) (07/20/87)
Silicon Systems SSI 201 Integrated DTMF Reciever. I bought mine for $5.00 including the crystal and a 22 pin socket. Outputs in binary (except that Zero is coded 10) Uses 12V supply and a Color Burst (3.579545 MHz) Crystal. The application notes even point out how to add pusle dial detection to the chip. -Ron
hanley@cmcl2.NYU.EDU (John Hanley) (07/22/87)
In-Reply-To: <1377@mit-amt.MEDIA.MIT.EDU> Using audio sounds good, especially since for debugging purposes you can just listen to a radio receiver. However, especially since you don't have them readily at hand, I'm not convinced that DTMF chips are the way to go. You can easily get VCO's to hum at any frequency you want by tweaking discrete resistors, and further you can build a frequency detector with a single 747 dual op amp: one side accepts audio input and acts as a bandpass filter, the other side acts as a comparator and just cleans up the analog so it's TTL on the output (or it could act as a Schmitt trigger, which still requires but a single op amp). This might be simpler than DTMF because now you've only got one frequency to worry about at a time instead of two. Of course, I'm blindly assuming that you've got enough bandwidth and steep enough filters for all these frequencies to give each other enough breathing room. If need be you can make the filters steeper by adding another stage or two, and the whole thing would still fit on a single (quad) chip. Of course, if some DTMF chips drop into your lap, by all means use them, but I tend to think in terms of what I can build _now_. What?!? You don't have a drawer full of 741's? Shame on you! If for some reason you're not real big on op amps, you can use a 567 tone decoder to do the same thing, but I'm guessing you don't have a whole lot of those lying around or you'd be using those instead of posting to the net. P.S.: I almost recommended the use of 555 timers to generate your tones but then caught myself because I think you want sinusoidal tones to transmit. I did this because I recall reading something on modems that mentioned that mod/demod is done because the phone system has low bandwidth and is optimized for the human voice, so sine waves make it through the phone system _much_ better than square waves. Why is this? I understand that the rapid hi-lo transitions count as high frequency transitions and thus will be attenuated, but it seems to me that the worst case should be that you put a square wave in and get the corners lopped off so the output looks kind of sinusoidalish. But since an X volt p-p square wave carries more power than an X volt p-p sine wave, you should get a better S/N ratio at the output using square simply because you applied more signal. Why doesn't this work? --John Hanley, / / ____ __ __ System Programmer, Manhattan College [ ..cmcl2!mc3b2!jh ] /__/ /__ / /-< /-/ Researcher, NYU Ultracomputer Labs [ Hanley@NYU.arpa ] "The Ultracomputer: to boldly go in log N time where no N processors have gone before." Addendum: Bandpass active filter (40 db/decade, I think -- it's 2nd order) R R +----/\/\/\/-----+-----/\/\/\/-----+ | | | ----- C ----- C ----- C ----- ----- ----- | | | +----------------+-----------------+ | | R/12 | Rin | |\ +--/\/\/\/--GND | audio in o-----/\/\/\/----+---| -\___________________________+------o Vout +-| +/ | |/ | GND where Rin is whatever input impedance you would like to present to your RF reciever circuitry, and RC determines the detection frequency: f = sqrt(3) / ( 2 pi R C )
rep@genrad.UUCP (Pete Peterson) (07/22/87)
In article <17966@cmcl2.NYU.EDU> hanley@nyu.arpa (John Hanley) writes: #> But since an X volt p-p square wave carries more #> power than an X volt p-p sine wave, you should get a better S/N ratio #> at the output using square simply because you applied more signal. #> Why doesn't this work? #> It does work, provided that the 3f, 5f, etc harmonics of the square-wave don't cause you any problems. The square wave has a fundamental frequency content which is about 1.27 times the sine wave giving about 1.6 times the power. Of course the square wave has twice the power of the sine wave, but the power in the harmonics doesn't help your S/N ratio. #> #>Addendum: Bandpass active filter #> #> R R #> +----/\/\/\/-----+-----/\/\/\/-----+ #> | | | #> ----- C ----- C ----- C #> ----- ----- ----- #> | | | #> +----------------+-----------------+ #> | | R/12 | #> Rin | |\ +--/\/\/\/--GND | #>audio in o-----/\/\/\/----+---| -\___________________________+------o Vout #> +-| +/ #> | |/ #> | #> GND #> Simpler circuit with roughly equivalent behavior and many fewer parts: Rin audio in o-----/\/\/\/------+------o Vout | | GND Unless you have a pile of op amps and R's and C's which are burning a hole in your junk box (or other parts storage facility) and you are extremely poverty stricken and take great delight in building and tuning multiple bandpass filters, the integrated DTMF encoders/decoders are definitely the way to go. pete peterson {decvax,linus,wjh12,mit-eddie,masscomp}!genrad!rep
larry@kitty.UUCP (Larry Lippman) (07/22/87)
In article <1319@genrad.UUCP>, rep@genrad.UUCP (Pete Peterson) writes: > Unless you have a pile of op amps and R's and C's which are burning a hole in > your junk box (or other parts storage facility) and you are extremely > poverty stricken and take great delight in building and tuning multiple > bandpass filters, the integrated DTMF encoders/decoders are definitely the way > to go. Right on! Besides, most of the integrated receivers have far superior selectivity (read spurious signal rejection) than any receivers built with discrete tone detectors. Not only can integrated receivers implement more filter poles than is convenient for discrete construction, but some of the newer integrated receivers use switched-capacitor filters. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rocksanne|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
phd@speech1.cs.cmu.edu (Paul Dietz) (07/22/87)
In article <17966@cmcl2.NYU.EDU> hanley@nyu.arpa (John Hanley) writes: >Addendum: Bandpass active filter (40 db/decade, I think -- it's 2nd order) > > R R > +----/\/\/\/-----+-----/\/\/\/-----+ > | | | > ----- C ----- C ----- C > ----- ----- ----- > | | | > +----------------+-----------------+ > | | R/12 | > Rin | |\ +--/\/\/\/--GND | >audio in o-----/\/\/\/----+---| -\___________________________+------o Vout > +-| +/ > | |/ > | > GND > >where Rin is whatever input impedance you would like to present to your >RF reciever circuitry, and RC determines the detection frequency: > f = sqrt(3) / ( 2 pi R C ) I don't think this is what you meant. None of the RC's (except Rin) are doing anything! Paul H. Dietz Carnegie Mellon University
asm@utcsri.UUCP (07/30/87)
In article <1867@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >In article <1319@genrad.UUCP>, rep@genrad.UUCP (Pete Peterson) writes: >> Unless you have a pile of op amps and R's and C's which are burning a hole in >> your junk box (or other parts storage facility) and you are extremely >> poverty stricken and take great delight in building and tuning multiple >> bandpass filters, the integrated DTMF encoders/decoders are definitely the way >> to go. > > Right on! Besides, most of the integrated receivers have far >superior selectivity (read spurious signal rejection) than any receivers >built with discrete tone detectors. Not only can integrated receivers >implement more filter poles than is convenient for discrete construction, >but some of the newer integrated receivers use switched-capacitor filters. You can get a DTMF receiver for less than it will take to put one together using op-amps etc. Just about everyone makes a dozen chips to do this these days. For the fun of hacking though, nothing beats putting the stuff together from scratch. It can be done using two bandpass filters and two phase-locked loops (better than doing 8 filters!) anees munshi
pff@thumper.bellcore.com (Peter Ferris) (01/26/89)
Greetings, Excuse me if this is something that's been asked 583 times already, but I'm attempting to build a DTMF (Touch-Tone) --> RS-232 converter. I've seen the units in the magazines for $90, but it seems to me that's about $75 too much! Does anybody have any experience in this area? My specific questions are: 1) I guess the choices seem to be the SSI-202 (Radio Shack = c.$13.00) or the SSI-204 IC's. Who makes these (Samsung?), and what is the difference between them? 2) How should I (or SHOULD I) control baud rate; eg; dipswitch and/or software? Or would it be simpler / cheaper / "better" to decide on a "fixed" baud rate (would 300 baud be fast enough for a very rapid burst?)? 3) I need to decode all <16> characters (0-9, A-D, # & *). 4) The circuit should be somewhat "forgiving" in that the DTMF will be decoded from a variety of audio sources, ie; scanner, handie-talkie, vcr, and other audio sources - but the audio could have static or other artifacts in it. Permit me to add that this project is what we call a "G-Job" - it's for my own personal pleasure / experimentation. If anyone has any suggestions, comments or schematics on this rainy day project I'd sure appreciate hearing from you. Best bet is Internet E-mail. Many Thanks in Advance, Pete Ferris, N5KBD pff@thumper.bellcore.com
byron@pyr.gatech.EDU (Byron A Jeff) (01/26/89)
-Greetings, -Excuse me if this is something that's been asked 583 times already, but I'm -attempting to build a DTMF (Touch-Tone) --> RS-232 converter. I've seen the -units in the magazines for $90, but it seems to me that's about $75 too much! -Does anybody have any experience in this area? I helped build a DTMF decoder for a school project last quarter. I also currently have a homebuilt 68010 computer with a rs232 port. Price should be between $20-$25 depending on what you use. - -My specific questions are: - -1) I guess the choices seem to be the SSI-202 (Radio Shack = c.$13.00) or the -SSI-204 IC's. Who makes these (Samsung?), and what is the difference between -them? Silicon Systems Incorporated. Tustin, Ca. (714) 731-7110. I happen to have their data book in my office. Let's see... Description... SSI-202 - The SSI 202 (and 203) are complete DTMF receivers detecting a selectable group of 12 or 16 standard digits. No front end prefiltering is needed. The only externally required components are an inexpensive 3.58-MHz telvision "colorburst" crystal (available from Radio Shack among others - Ed.) and a bias resistor... Both are CMOS, use 5V and packaged in a 18 pin DIP SSI-204 - 14 Bit version of the 202. Uses same external components. It's missing some of the more esoteric pins like Inhibit last row decoding, Binary coded 2 of 8, Clear Data available, early detection. Real big loss ;-) Both have 3 state outputs and a data available output for direct connection to a microcomputer. - -2) How should I (or SHOULD I) control baud rate; eg; dipswitch and/or software? -Or would it be simpler / cheaper / "better" to decide on a "fixed" baud rate -(would 300 baud be fast enough for a very rapid burst?)? Well... Let's see (300 b/s) * (1 char / 10 bits) = 30 char / s So 1 char every 33 ms. Ok. Now according to the data sheet both the time to detect the tone and then the following pause is 40 ms apiece. So with 80 ms to do 1 digit 300 bps should be plenty fast enough. - -3) I need to decode all <16> characters (0-9, A-D, # & *). No problem. Both decoders do the job. - -4) The circuit should be somewhat "forgiving" in that the DTMF will be decoded -from a variety of audio sources, ie; scanner, handie-talkie, vcr, and other -audio sources - but the audio could have static or other artifacts in it. The data sheet claims to be able to detect with S/N of 12db. That's really really noisy. They warn that if you have signal above 28kHz it can alias back into the audio range and that it needs to be filtered. - -Permit me to add that this project is what we call a "G-Job" - it's for my own -personal pleasure / experimentation. If anyone has any suggestions, comments -or schematics on this rainy day project I'd sure appreciate hearing from you. -Best bet is Internet E-mail. Two ideas immediatly spring to mind. No micro -------- ____------- ------ ----- |------|____| | | | |MAX| audio in ----| DTMF |____|EPROM|-8 data lines-|UART|--|232|--ascii serial out |------|____| | | | | | | ------- ------ ----- | | |-Data valid from DTMF to UART send Rather quick and dirty. Whenever the DTMF decoder receives a digit the EPROM changes it to ascii, the data available of the decoder does a write to the UART which sends the converted value out the serial port. By using a MAX 232 tranceiver you can do the whole circuit with 5V supply. Micro ----- Replace the EPROM and UART with a EPROM microcontroller like a 68701 or an 8051. Of course then you can program it on the fly with different baud rates and different conversions by sending data back out the serial port. Or put an encoder in the circuit for two way communication. Or any number of rather nifty things. Another part you may want to look at is the SSI 2090C. All the functionality of the 202 plus an encoder and a simplistic ring detection system. - -Many Thanks in Advance, Sure enough. Let me know if anything comes of it. - -Pete Ferris, N5KBD -pff@thumper.bellcore.com BAJ -- Another random extraction from the mental bit stream of... Byron A. Jeff Georgia Tech, Atlanta GA 30332 Internet: byron@pyr.gatech.edu uucp: ...!gatech!pyr!byron
scotts@bu-cs.BU.EDU (Scott Statton) (01/26/89)
Two points about the SSI 20x series of decoders. The DTMF detector works VERY nicely -- we put it through our "torture" test and it passed with flying colors. What, you may ask, is the torture test? Pick the ickiest Inter-Exchange Carrier [we chose one famous for telegrams, not so famous for phone service]. Call a RASU on the opposite coast [This was done in Boston, so RASU was in Mountain View, CA] and call back in to the decoder under test. Send DTMF at very high rate [12 digits per second] and count total number of errors in a 5 mintue test. As I recall, the chip weighed in at 7 mis-decodes. Other point: They also make a very nice MF decoder called the SSI-207. Unfortunately, they're about $70 in small quantities. It appears not everybody uses MF as much as DTMF. Great for those semi-secure application machines. Try & bust me for Blue-Boxing -- my computer uses it for remote control applications. [Or, I'll just use the test-frame at work] scotts@buit.bu.edu ... aka N1GAK ... "The full-time phone hacker who spends an unholy amount of time with his Dan-Ray CTSS-4000"
larry@kitty.UUCP (Larry Lippman) (01/26/89)
In article <1441@thumper.bellcore.com>, pff@thumper.bellcore.com (Peter Ferris) writes: > Excuse me if this is something that's been asked 583 times already, but I'm > attempting to build a DTMF (Touch-Tone) --> RS-232 converter. I've seen the > units in the magazines for $90, but it seems to me that's about $75 too much! > Does anybody have any experience in this area? You rang? :-) > 1) I guess the choices seem to be SSI-202 (Radio Shack = c.$13.00) or the > SSI-204 IC's. Who makes these (Samsung?), and what is the difference between > them? They are both made by Silicon Systems. Both of these IC's are almost identical, but the SSI-202 is a somewhat better quality device with a few more control lines (which may be unnecessary for your application, though). > 2) How should I (or SHOULD I) control baud rate; eg; dipswitch software? > Or would it be simpler / cheaper / "better" to decide on a "fixed" baud rate > (would 300 baud be fast enough for a very rapid burst?)? Well, if *I* were going to build this device, I would use an 8571 (or 8031 with external eprom) single-chip microprocessor with built-in uart; the programming is trivial and can be done in less that 50 lines of assembly language. The microprocessor could provide two-way serial communication to set options via software command. You won't have any convenient software method of setting options without some intelligence. However, you could probably get away with a simple uart with internal baud rate generator for hardware "programmed" operation. You can use the valid tone detect pair output (DV pin) to strobe the uart transmitter. For fixed baud rate, 300 baud is fine. No DTMF system will EVER dial that fast; typical autodialing speed is 10 digits/sec. > 3) I need to decode all <16> characters (0-9, A-D, # & *). No problem. > 4) The circuit should be somewhat "forgiving" in that the DTMF will be decoded > from a variety of audio sources, ie; scanner, handie-talkie, vcr, and other > audio sources - but the audio could have static or other artifacts in it. That's a tough call. One basically gets what one pays for, and these ciruits are not THAT forgiving - but they may be fine for your application. If you want forgiving circuits, you will have to spent more $$$ and go to a quality device like those made by Tel-Tone or Mitel. Tel-Tone is on the Net, so maybe someone will give you more specific advice about their products. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {att|hplabs|mtune|utzoo|uunet}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
sl@van-bc.UUCP (pri=-10 Stuart Lynne) (01/26/89)
In article <7139@pyr.gatech.EDU> byron@pyr.UUCP (Byron A Jeff) writes: >-attempting to build a DTMF (Touch-Tone) --> RS-232 converter. I've seen the >I helped build a DTMF decoder for a school project last quarter. I also >-SSI-204 IC's. Who makes these (Samsung?), and what is the difference between Now that we can decode DTMF, how hard would it be to add some functionality to product a dial tone. For example the device should go offhook when "DTR" is raised. A dial tone is produced when RTS goes high and DTMF recogition starts. Dial tone should disappear after first digit typed, or when RTS is dropped (whichever comes first). It would also be nice to be able to plug this in between a modem and phone line, so the ability to make modem think the phone is ringing after you have gathered data from person would be nice. (It could also be between modem and computer serially so you wouldn't need a second serial port for it). -- Stuart.Lynne@wimsey.bc.ca {ubc-cs,uunet}!van-bc!sl Vancouver,BC,604-937-7532
jpd@usl-pc.usl.edu (DugalJP) (01/27/89)
Pete, I recently purchased the Radio Shack DTMF decoder chip. Looks very easy to interface. Although you asked about RS-232 interfacing, I think it would be easy to interface it to a PC's parallel port. Phil Karn posted some time back on rec.ham-radio about how to modify a parallel IO card for 8-bit input. I'm not sure a stock card would have enough input lines .... I think you'd need 5 (4 data plus strobe). -- James -- -- James Dugal, N5KNX USENET: ...!{dalsqnt,killer}!usl!jpd Associate Director Internet: jpd@usl.edu Computing Center US Mail: PO Box 42770 Lafayette, LA 70504 University of Southwestern LA. Tel. 318-231-6417 U.S.A.
gbell@pnet12.cts.com (Greg Bell) (01/27/89)
I've built DTMF decoding circuits for a variety of applications. The SSI-202 chip seems to work well. In fact, I've got one hooked up to a microcontroller project right now! By the way, SSI stands for Silicon Systems Inc. You might also want to look into Teletone's DTMF decoders. For Teletone's number, call 1-800-555-1212 (800 information). As for interfacing the output of one of these to RS-232, you need a UART. This is a chip that will take the 4 bit output of the decoder and convert it into serial information. There are several of these available. General Instruments makes one called the AY-3-1015. Both of these chips are extremely easy to use. However, you might have a problem with the noise levels of the signals you are trying to feed in. Seems to me like the success or failure of your project might lie in how good the input amplifier circuit is. The app. engineers at Teletone might be able to help you out with this... Greg Bell_________________________________________________________ Hardware hacker | Electronics hobbyist | UUCP: uunet!serene!pnet12!gbell EE major at UC San Diego |
gilley@goofy.apple.com (Tom Gilley) (01/27/89)
In article <1441@thumper.bellcore.com> pff@thumper.bellcore.com (Peter Ferris) writes: > I'm attempting to build a DTMF (Touch-Tone) --> RS-232 converter. Hints: The Radio Shack (on sale today) DTMF decoder will give you four parallel bits which you can connect to the parallel input side of a simple UART. The AY-3-1015D UART for TTL or the IM6402 UART for CMOS are easy to use. Tom Gilley
keith@m5.UUCP (Keith J. McQueen) (01/28/89)
Myself along with a group from our local Ham Radio ARES group has designed a DTMF decoder circuit that we use for DTMF signalling, remote control and paging. One of the many features it incorporates is a CMOS level ASCII serial output (RS-232 but 5v levels) of all tones recieved. The project uses a microprocessor for control, and draws about 12 microamps when no audio is present. Costs about $50 to build. This could be what you are looking for.