Sounds like the best way since the PIC will be doing other things....to do it external. Who distributes Holtek? David Van Horn wrote:> Just looking for comments I've worked with a bunch of different implementations over the years, in telephony apps. It's all about the compromises. You can get a nice DTMF encoder from Holtek for $0.25 in relatively small quantities. That's a lot of codespace and processor time freed up, and the chip is easy to talk to. Decoders are a bit more, but I think you'd be hard pressed to get equal performance in all respects, from a software solution, especially if you are looking to do anything else in the same processor. Making something that sort of works is one thing. Making something that works with good dynamic range, twist tolerant, capable of detecting in 40mS, tolerant of noise.. That is likely to involve significant development time if it can be done at all. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist