Datasheet

logfile.print(now.year(), DEC);

logfile.print("/");

logfile.print(now.month(), DEC);

logfile.print("/");

logfile.print(now.day(), DEC);

logfile.print(" ");

logfile.print(now.hour(), DEC);

logfile.print(":");

logfile.print(now.minute(), DEC);

logfile.print(":");

logfile.print(now.second(), DEC);

#if ECHO_TO_SERIAL

Serial.print(now.get()); // seconds since 2000

Serial.print(", ");

Serial.print(now.year(), DEC);

Serial.print("/");

Serial.print(now.month(), DEC);

Serial.print("/");

Serial.print(now.day(), DEC);

Serial.print(" ");

Serial.print(now.hour(), DEC);

Serial.print(":");

Serial.print(now.minute(), DEC);

Serial.print(":");

Serial.print(now.second(), DEC);

#endif //ECHO_TO_SERIAL

The first important thing is the delay() call, this is what makes the Arduino wait around until

its time to take another reading. If you recall we #defined the delay between readings to be

1000 millseconds (1 second). By having more delay between readings we can use less

power and not fill the card as fast. Its basically a tradeoff how often you want to read data

but for basic long term logging, taking data every second or so will result in plenty of data!

Then we turn the green LED on, this is useful to tell us that yes we're reading/writing data

now.

Next we call millis() to get the 'time since arduino turned on' and log that to the card. It can

be handy to have - especially if you end up not using the RTC.

Then the familiar RTC.now() call to get a snapshot of the time. Once we have that, we write

a timestamp (seconods since 2000) as well as the date in YY/MM/DD HH:MM:SS time

format which can easily be recognized by a spreadsheet. We have both because the nice

thing about a timestamp is that its going to montonically increase and the nice thing about

printed out date is its human readable

Log sensor data