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Dual-tone multi-frequency signal generator and detector

Posted on Wednesday, July 4th, 2012 in code by DP

Robots wrote a open source Dual-Tone Multi-Frequency signal generator and detector for his STM32 based development board. The code is available via github.

DTMF generator is based on AVR314 appnote, and the detector is my practice in signal processing using “Goertzel algorithm”. Everything is written for integer/fixedpoint arithmetics. (no floats at all)…

Generator generates signal using PWM, by changing the duty cycle each period. Two sine signals (low and high) are generated using LUT and mixed before feeding into the PWM.

Detection is done by using 8 simultaneous signal detectors. One for each frequency in dtmf. After 205samples energie of each frequency is calculated and peak detected.

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