A weblog focused on interesting circuits, ideas, schematics and other information about microelectronics and microcontrollers.
Software DTMF decoder
DTMF (the phone dialing tones) is often decoded with a special IC. Here is a pure SW implementation in the PIC18F877 chip.
Cite: The software DTMF Decoder is based on a modified Goertzel algorithm. A good source of explanation for the this algorithm and how to implement it using a DSP can be found in "Modified Goertzel Algorithm in DTMF Detection Using the TMS320C80" – Application Report from Texas Instruments.
In order to implement this algorithm on a such small processor like a 16 series PIC it was necessary to switch to integers, an finally to work with bits. A good source of inspiration wasby Scott Datallo