Post by thread:Frequency counter

I wrote a "guitar tuner" application that detects which guitar string is being played, then tells you if it's sharp of flat. I have yet to come up with the analog interface, but if you feed in nice clean square waves, it works. I'll send it to anyone who's into it. My basic approach to counting frequency is to have a nice fast xtal clock, then have the RTCC prescaled by about 32, 16 at least. During execution you poll the input pin once every RTCC tick, and count how long from one low-to-high transition to the next. That's your period. I used a lookup table to determine the frequency, but you could also do the math, if you were truly adventurous. David -- Their address sums up their attitude: One Microsoft Way http://www.rt66.com/dthomas/

> I wrote a "guitar tuner" application that detects which guitar string is > being played, then tells you if it's sharp of flat. I have yet to come > up with the analog interface, but if you feed in nice clean square waves, > it works. I'll send it to anyone who's into it. That's sounds pretty cool. I wouldn't mind a copy of it. I was thinking about something very similar. An interface from guitar to midi. I could use this as the front end! I'm not sure what the interface would sound like? I guess your circuit just picks up the fundamental note. What happens when you play a chord? It's probably quite hard to pick more than one note. Hmmm, I guess a fourier transform would have to be involved and that would probably blow the PIC capacity. Just a thought. Paul.

[...] > An interface from guitar to midi. I could > use this as the front end! I'm not sure what the interface would sound > like? > > I guess your circuit just picks up the fundamental note. What happens > when you play a chord? It's probably quite hard to pick more than one > note. Hmmm, I guess a fourier transform would have to be involved and > that would probably blow the PIC capacity. Just a thought. Well, how do the existing MIDI guitars work? Do they have 6 channel pickups or do they just have regular pickups and some heavy-duty DSP? For all I know, both techniques are in use. Quite possibly others that I haven't thought of, too. I wouldn't mind having a box to plug my guitar into that picks apart the analog signal and produces MIDI. That would probably render the volume and tone controls useless, though. The square wave approach described in the posting that started this thread wouldn't work very well for serious music, even if it can be made to handle chords. There are other parameters such as the envelope which are lost in the 1 bit digitization. But then again, the original application was a tuner, not MIDI.

The goal of my guitar tuner project was not to be able to detect notes in a chord or even to be particularly good at following a single melody line. It was just to be able to identify a nice loud, steady pitch and tell you if the string is sharp or flat. So far I've never gotten it to work in practice, but I have a plan for how to make it work. I tried using an amplifier and schmidt trigger to eliminate harmonics and give a squared output. This works, but only for the first second or so after the string is struck. If you look on a scope when you hit a guitar string, you'll see that the fundamental is reasonably strong initially, but it is soon eclipsed by harmonics. I think it's the second harmonic that was the real killer but I can't remember for sure right now. Anyway my plan is to detect the frequency the same way I do now, but if I start seeing that the pitch appears to increase suddenly, I'll just ignore any transitions that don't arrive near the expected times. This should have the effect of discarding the harmonics and yielding a longer useful tuning time. It would be interesting to also pursue the generation of MIDI from a guitar signal, though I think many serious applications would require DSP horsepower. My detector is reasonably fast at identifying the pitch. I have some code that sends MIDI (a nice little subroutine) if anyone is interested. Hmm that's two programs I've volunteered to pass around. What's the best way to do this? I can put them up on my web page, in an ftp directory, post them to the list, or email them to individuals. How is this best handled? David -- Their address sums up their attitude: One Microsoft Way http://www.rt66.com/dthomas/

In message <m0sTjoW-0000mjCKILLspamdc.cis.okstate.edu>, Paul Nolan writes: >I guess your circuit just picks up the fundamental note. What happens >when you play a chord? It's probably quite hard to pick more than one >note. Hmmm, I guess a fourier transform would have to be involved and >that would probably blow the PIC capacity. Just a thought. There is a more fundamental problem, here. Whether the frequency counter is made from a PIC, vacuum-tubes, or mechanical relays salvaged from old soda machines, it will probably work on the same principle in that there will be a counting device that is stepped through its count by the incoming signal until the time base times out and the count on the counting device is needed. The time base will reset the counter and put the last count on the display and the count starts all over again until the next reset. The whole system is based on the idea that the signal is composed of a single periodic wave form. A chord would produce a more complex series of patterns that would definitely make the counter count, but the result would be worthless because the pulses did not arrive in a steady procession. Imagine an extreme case in which a counter with a 1-second time base is connected to a signal that consists of 5 pulses of a 1Mhz carrier every 10 seconds. For 9 of 10 seconds, the counter will read 0 because it saw nothing. During that tenth second, it will see the five pulses and show 5 Hertz because that's what the counter had in it when reset. The output can't even tell you if those 5 pulses were really 1us apart or 20us. Maybe the time base caught the counter just as it got a couple of the pulses such that the display reads two and then three during the next sample. It might be a bit confusing. I am sorry to have taken so much band-width, but this has been a very good discussion that has touched on some fundamental issues which come up when we want to digitally read signals and try to make sense of them. Martin McCormick WB5AGZ Stillwater, OK 36.7N97.4W in Tornado Ally OSU Center for Computing and Information Services Data Communications Group

try Terry Weeder http://www.infinet.com/~dhoehnen/weeder/wtcnt-k.htm, He has a kit that has all the parts and a really nice pcb board. at $46us it would be hard to trace down the parts for this project let alone figure out the neat preamp etc. Mine works great! Regards Wil Reeder Vancouver Canada ---------- > From: wayne galaugher <.....waynegKILLspam.....ICAN.NET> > To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU > Subject: frequency counter > Date: Wednesday, April 08, 1998 8:52 PM > > Need some code to create a low frquency counter with 4 digit display > using 16F84. Have 4x2 LCD.

I have just finished a 7 digit auto ranging frequency counter that uses an lcd display I have use a design from the net published 1994 in popular electronics by Terry J. Weeder an sold as a kit by him at http://www.weedteck.com for a very good price. I did not get the kit (postage to Greece, forget it) Anyway I have fixed the typo's and ommisions and ported it to a 16f84 It looks good and works well If anyone wants the code let me know PS: anyone in the US it would be better to get the kit, the kit price looks cheaper than the sum of all the parts. -- Peter Cousens email: cousensspam_OUTher.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)

Paul B. Webster VK2BZC wrote: SNIP > I tried making a URL out of that and it was nonsense. Were you > perhaps thinking of: http://www.weedtech.com/ ? Yes sorry my mistake -- Peter Cousens email: @spam@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)

> Hi Peter, > > > If anyone wants the code let me know > > I'm interested! Could you please send me the code? > Thank you very much. > > Greetings from Italy, I have had 16 replies like this so far Does anyone have a web page they wan't to put it on The zip file is 76K (circuit.gif, .asm and .hex files) -- Peter Cousens email: KILLspamcousensKILLspamher.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)

Darren, I use the parallax assembly language and I want something thats in that language thank you for all your help. Does ant one out there have such routine written i parallax assemblers language? //Ross ---------- > From: Darren Logan <RemoveMEDAZLOGANTakeThisOuTAOL.COM> > To: spamBeGonePICLISTspamBeGoneMITVMA.MIT.EDU > Subject: Re: frequency counter > Date: Sunday, December 13, 1998 4:00 PM > > Use the PIC BASIC Pro compiler. > It has a 16-bit COUNT function built in !!!. > > Here's an example of how easy it is to count the number of pulses on a pin > over a 100mS period: > > COUNT Pinnumber, Period, IntoVariable > > Or COUNT 0,100,Word > > Easy or what ?? > > Darren

H. Ross wrote: > > Hi, Guys: > > I'm looking for some code that written in parallax language for a freqency > couter using a > PIC16F84. I was told the scott edwards has such code on how to count pulse > in 10us > increments using parallax asm. Help! > > //Ross Scott Edwards on-line version PIC Source book at http://www.dontronics.com/see.html may help you Don McKenzie TakeThisOuTdonEraseMEspam_OUTdontronics.com http://www.dontronics.com Don's Download Dungeon: http://www.dontronics.com/download.html Australian Electronics Ring http://www.dontronics.com/aering.html

About a year ago I offered the code (ported from 16c54) for a seven digit auto_ranging lcd display frequency counter I lost the code in a hard disk crash, could somone please send the file back to me Please reply privately as I'm unsubscribing I think it's time to move on Goodby and good luck -- Peter Cousens email: RemoveMEp.cousensTakeThisOuTcwcom.net or p.cousensEraseME.....virgin.net smail: 48, Yarmouth Cresent, London, N179PQ, England.

Dear Mitchel Monteiro! A (16F84) frequency counter designed by Peter Halicky is for examle on the: http://www.ubasics.com/adam/pic/archive.shtml Best regards Pavel {Quote hidden}> -----Pùvodní zpráva----- > Od: Mitchel - task [SMTP:EraseMEmitchelTASK.COM.BR] > Odesláno: 2. listopadu 1999 14:19 > Komu: RemoveMEPICLISTEraseMEEraseMEMITVMA.MIT.EDU > Pøedmìt: Frequency Counter > > Please, I need a project Frequency Counter with PIC and low coast. > Does anybory know where I can find it ? > > > Mitchel Monteiro

There's a good project, uses a 16F84, that I grabbed a while ago - does up to 50MHz using the prescaler on the 'F84 (don't see the URL in my bookmarks here - Folks? Might use a 'C84 also.) I can just e-mail it to you, if you want, off-list, once I find it; I found another that uses a 16C54, here in a small file. (I'll have to drop to DOS to find it, Windows just gets in the way / crashes. Need to run mail stuff, will be back in 2-3 hours.) Mark Mitchel - task wrote: > > Please, I need a project Frequency Counter with PIC and low coast. > Does anybory know where I can find it ? > > Mitchel Monteiro -- I do small package shipping for small businesses, world-wide.