Mike, The problem here is you are not simply dipping a grid, you are interfacing a 200+ Mhz tiny RF signal to a digital chip. That is why I mentioned the real crux of this project is in "RF design/layout/matching/amplification/sensing/etc" - taking that tiny signal and converting successfully to 0-5v. Once you have picked up and amplified the "sine", then you can use an analog prescaler and/or schmitt trigger to square up for presentation to the PIC. The PIC can probably accept a sinewave ok, as long as it is large enough [about +/-2v], shifted into the range 0-5v, and slews fast enough so that noise doesn't cause false counts. AN592 talks about using Timer0 of the '84 for counting. I mentioned it mainly for reference. The '628 is probably too new to find much specifically about using it. However, the Timer1 module is the same as on the '74/'76/'77/'874/'876/'877, so you can look at those chips. Also, I don't know anything about the el cheapo programmer and the '628. Again, the '628 is so new, not everything out there supports it. - dan =============== At 10:43 PM 8/9/01 -0000, you wrote: >Dan, > On the oscillator part of the circuit, it is too easy actually. The >user of the Grid Dip Oscillator adjusts a knob to vary the frequency of the >circuit. As the frequency is adjusted the current going through the meter >will change if it matches the resonant circuit by dipping. These hand held >pieces of test equipment have been around for over 60years to my knowledge >and are beautiful in their simplicity. They origionally consisted of a >single vacuum tube that had the plug in coils. The tricky part of the >origional design was that the coils had to be wound so that the readout on >the printed dial matched the actual frequency within reason. In this >application, that is totally unimportant as the digital frequency counter >does the job. Therefore, I can use handwound coils that vary considerably >from each unit produced just as long as the frequency readout is correct, >everything is A OK. > A 180mhz digital readout would really be perfect for me. > >1st question-do you think I'll be able to use the sine wave into the >counter, or would I need to "shape it" for the PIC?? > >2nd question-from what you described origionally, the 74AC74 would be great. >I'm not looking for 1hz resolution or anything. As a matter of fact 10khz >or 1Khz resolution would be great! Do you agree, or do you still feel that a >prescaler is better? > >3rd question-is the AN592 related to the 16F84, or PIC16F628? > >4th question-do you think the "el cheapo" programmer from Myke Predko's book >will work with the PIC16F628 if I go that route? > >Thanks again/regards, >Mike >----- Original Message ----- >From: "Dan Michaels" >To: "Mike Kendall" >Sent: Friday, August 10, 2001 3:15 AM >Subject: Re: [PIC]: Building a "counter" w/PIC16F628 > > >> Mike Kendall wrote: >> >Dan, >> > Yes, I will be counting analog signals out of an oscillator circuit. >> >These will/should be a clean sine wave. I will describe my project. I >was >> >disgusted with the high price of simple analog grid dip oscillators. The >3 >> >and 4 decade old units were going quite high and the new units were >around >> >100 bucks for an analog meter face type unit with little accuracy. >> ........... >> Ideally, the circuit >> >will work up to 250mhz, but up to 180mhz would be outstanding as it would >> >cover the marine band, 2meter ham band and down to hopefully 1.8 mhz >(even >> >lower would be better). >> .......... >> >> >> Mike, from what you describe, the PIC part of this should be fairly >> easy. Check the appnote, AN592, that I mentioned for prelim info. >> Other Mchp appnotes discuss interfacing LEDs/LCDs - AN590, AN529, >> AN563. >> >> The harder part looks like the analog front end to 250 Mhz. Does >> sound like a prescaler chip is in order - plus of course correct >> RF design/layout/matching/amplification/sensing/etc. This part >> requires a lot more savvy, I think, than writing a few lines of >> PIC code. A 16:1 or 32:1 prescaler should put you into the correct >> range for the PIC. >> >> good luck, >> - dan >> ============= >> > > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads