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위 코드시 아두이노 설정

주파수 필터링

Blinks built in pin13 LED on a 16mhz Arduino when it detects a 700 hz tone
which is inside of 1, 2, and 3 buttons (but not the others) on your phone's keypad,
Othwerise google for a tone generator on the web or an app for your phone.
I like this one http://onlinetonegenerator.com/

Frequency sampling is .. squishy business. Be prepared to mess with the
numbers below until you get something you like.

This work is entirely based on the Kevin Banks code found at
http://www.embedded.com/design/embedded/4024443/The-Goertzel-Algorithm
so full credit to him for his generic implementation and breakdown. I've
simply massaged it into an Arduino library. I recommend reading his article
for a full description of whats going on behind the scenes.

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