Alan, DTMF decoding on a PIC is not a pain. It is, however, rather time consuming for the PIC. If you don't need to meet the latency requirements for the DTMF specification, there is a really nifty implementation in the September issue of Circuit Cellar magazine. The design is based on the Goertzel algorithm, however, by carefully choosing the sampling frequency for each tone, the design doesn't need to do any multiplies (the cosine term always evaluates to zero). The calculation becomes a simple subtraction that can easily be done with very little runtime use. Ken klumia@adelphia.net ----- Original Message ----- From: "alan smith" To: "Microcontroller discussion list - Public." Sent: Friday, September 23, 2005 10:30 AM Subject: [PIC] DTMF encoding/decoding > Well...after doing a bunch of searching around I've seen in some cases > where a PIC has been employed in both DTMF applications, but then even > some of the more seasoned designers have used an external chip to do that. > > So is DTMF just a real pain to do in a PIC? Of course its easier to do > externally but if you are short on space and cost is a concern...embedding > it into the PIC is the obvious choice I think > > Just looking for comments > > > --------------------------------- > Yahoo! for Good > Click here to donate to the Hurricane Katrina relief effort. > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist