This library is for decoding the DCF77 time signal broadcasted by the german PTB (Physikalisch-Technische Bundesanstalt) in Mainflingen.
I used the sample code written by Matthias Dalheimer (md@gonium.net) and adapted it so that it can be used as a library in other Arduino projects.
Modified by Maciej Baur (mbaur@wp.pl) to fix synced() function behavior.
To be able to use this code you have to hook up a special DCF77 receiver to your Arduino. I used the one sold be german electronics retailer Reichelt.
Unfortunately the Reichelt module has a very weak push-pull output which provides only around +/- 5uA.
To get usable readings out of it I used the following circuit:
+---|____|---+
| R3 |
____ |/c-------+------------|---o PIN2| SIG o--- | ____ | ---b | R1 | \e->-----+ | ____ | VDD o---+-------+-------+--- | --- | ____ | ---+---o +5V _ | _ | R2 D1 /_\ C1 C2 |
|---|
GND o---+-------+-------+---+----------------o GND
D1: 3.9 Z-Diode C1: 100n Ceramic Capacitor C2: 100u Electrolytic Capacitor R1: 120k Resistor R2: 2.2k Resistor R3: 10k Resistor
To amplify the signal there is a 2N2222 Transistor between R1 and PIN2.
For a tutorial on how to install new libraries for use with the Arduino development environment please refer to the following website: http://www.arduino.cc/en/Reference/Libraries
This library assumes that you have SIG hooked up to Arduino's PIN2. The reason for this is that most Arduino boards have two external interrupts: numbers 0 (on digital pin 2) and 1 (on digital pin 3). If you want to use PIN3 you would have to change the constant at the top of Funkuhr.cpp and change the interrupt number in attachInterrupt() from 0 to 1.