OF course there is always the MAXIM chip that does it. Take a look at the app note http://www.maxim-ic.com/appnotes.cfm/appnote_number/287/ln/en But I agree....do it in software. So mucn easier to control and maintain. I did mine in a simple macro. >From: Olin Lathrop >Reply-To: pic microcontroller discussion list >To: PICLIST@MITVMA.MIT.EDU >Subject: Re: [PIC]: Debounce Circuit >Date: Wed, 26 Feb 2003 09:59:58 -0500 > > > Vdd > > | > > .-. > > | | > > R1| | > > '-' > > | R2_ _R3 > > +--|___|----+--|___|-o PIC Schmidt trigger input pin > > | | > > \ o | > > \ --- > > \. ---104 Ceramic > > o | > > | > > | | > > === === > > GND GND > > > > > > R1 24K > > R2 100K > > R3 1K > >The main time constant should be between R1 and C. R2 is only there to >avoid welding the contacts, and can be eliminated for small enough values >of C. The purpose is to have a very small time constant going down and a >much larger one going up. R2 of 200ohms would be fine, with R1 at least >100x higher. The R1-C time constant should be a few 10s of milliseconds. > > >***************************************************************** >Embed Inc, embedded system specialists in Littleton Massachusetts >(978) 742-9014, http://www.embedinc.com > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads _________________________________________________________________ Add photos to your e-mail with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads