Datasheet

Now the code starts to talk to the SD card, it tries to initialize the card and find a

FAT16/FAT32 partition.

Next it will try to make a logfile. We do a little tricky thing here, we basically want the files to

be called something like LOGGERnn.csv where nn is a number. By starting out trying to

create LOGGER00.CSV and incrementing every time when the file already exists, until we

get to LOGGER99.csv, we basically make a new file every time the Arduino starts up

To create a file, we use some Unix style command flags which you can see in the

logfile.open() procedure. FILE_WRITE means to create the file and write data to it.

Assuming we managed to create a file successfully, we print out the name to the Serial port.

OK we're wrapping up here. Now we kick off the RTC by initializing the Wire library and

poking the RTC to see if its alive.

Then we print the header. The header is the first line of the file and helps your spreadsheet

or math program identify whats coming up next. The data is in CSV (comma separated

value) format so the header is too: "millis,time,light,temp" the first item millis is

milliseconds since the Arduino started, time is the time and date from the RTC, light is the

Wire.begin();

if (!RTC.begin()) {

logfile.println("RTC failed");

#if ECHO_TO_SERIAL

Serial.println("RTC failed");

#endif //ECHO_TO_SERIAL

}

logfile.println("millis,time,light,temp");

#if ECHO_TO_SERIAL

Serial.println("millis,time,light,temp");

#if ECHO_TO_SERIAL// attempt to write out the header to the file

if (logfile.writeError || !logfile.sync()) {

error("write header");

}

pinMode(redLEDpin, OUTPUT);

pinMode(greenLEDpin, OUTPUT);

// If you want to set the aref to something other than 5v

//analogReference(EXTERNAL);

}