[Back to Home Page]   Black DTMF Decoding Algorithm Decoding
DTMF tones on the minimum PIC hardware - a new algorithm. Roman
Black - 5th March 2011.  Note!! This page is about decoding
DTMF. If instead you want to generate DTMF I have a nice
sinewave DTMF generator algorithm in C code you can see here.
DTMF is Dual Tone Multi Frequency, (or "Touchtone") these are
the sounds made by telephones to dial a number. Each DTMF sound
is made by two frequencies which are mixed together.  Standard
DTMF encoding  DTMF decoding normally uses a specialty IC that
receives the DTMF waveform and "decodes" it to one of the 16
possible outputs, usually as a 4bit binary output. These IC's
are hard to get for hobby and project use, and can be expensive
in small quantities, and require extra components including a
3.79MHz xtal.  DTMF decoding can be done in software on a high
power microcontroller or DSP micro using FFT (Fast Fourier
Transform).  DTMF decoding can be done reasonably well in
software using mid power micros using