If you've ever wondered about the best way to detect dial and DTMF tones from a phone line, [Debraj] is your man. [Debraj] built a DTMF detector using the Goertzel algorithm. Normally, when we think about detecting tones, we pull FFT out of our bag of tricks. The Goertzel algorithm isn't as computationally complex as FFT and can be implemented on even the smallest microcontrollers. For the … [Read more...]