Here is a data logging sketch that I developed for a shield with an SD card and an optional DS1307 RTC.
It illustrates new features in V2 of the SdFat library.
It has time stamped files - Windows dir listing
04/06/2011 07:30 AM 684 LOGGER15.CSV
04/06/2011 07:51 AM 4,954 LOGGER16.CSV
04/06/2011 07:55 AM 606 LOGGER17.CSV
04/06/2011 08:02 AM 9,665 LOGGER18.CSV
C++ style I/O for simpler and better data formatting.
Code to print time and date to Serial.
DateTime now = RTC.now();
cout << now << endl;
The result is:
2011/4/6 7:57:41
Sample logfile - note zero fill in minutes and seconds.
millis,date time,sens0,sens1,sens2
141000,2011/4/6 7:59:58,211,209,203
142000,2011/4/6 7:59:59,211,209,203
143000,2011/4/6 8:00:00,211,208,203
144000,2011/4/6 8:00:01,211,208,203
145000,2011/4/6 8:00:02,211,208,203
146000,2011/4/6 8:00:03,210,209,203
Better error handling and messages.
init failure message:
Can't access SD card. Do not reformat.
SD errorCode: 1
No card or SPI problem?
To use this sketch install RTClib:
Install the new beta version of SdFat:
http://code.google.com/p/beta-lib/downloads/list
Here is the code:
// A simple data logger for the Arduino analog pins
#define LOG_INTERVAL 1000 // mills between entries
#define SENSOR_COUNT 3 // number of analog pins to log
#define ECHO_TO_SERIAL 1 // echo data to serial port
#define WAIT_TO_START 1 // Wait for serial input in setup()
#define ADC_DELAY 10 // switch ADC and delay for high impedence sensors
#define USE_DS1307 1 // shield has DS1307 RTC
#include <SdFat.h>
#include <SdFatUtil.h> // define FreeRam()
// file system object
SdFat sd;
// text file for logging
ofstream logfile;
// Serial print stream
ArduinoOutStream cout(Serial);
// buffer to format data - makes it eaiser to echo to Serial
char buf[80];
//------------------------------------------------------------------------------
#if SENSOR_COUNT > 6
#error SENSOR_COUNT too large
#endif // SENSOR_COUNT
//------------------------------------------------------------------------------
// store error strings in flash to save RAM
#define error(s) sd.errorHalt_P(PSTR(s))
//------------------------------------------------------------------------------
#if USE_DS1307
#include <Wire.h>
// get RTClib from Adafruit here
// https://github.com/adafruit/RTClib
#include "RTClib.h"
RTC_DS1307 RTC; // define the Real Time Clock object
// call back for file timestamps
void dateTime(uint16_t* date, uint16_t* time) {
DateTime now = RTC.now();
// return date using FAT_DATE macro to format fields
*date = FAT_DATE(now.year(), now.month(), now.day());
// return time using FAT_TIME macro to format fields
*time = FAT_TIME(now.hour(), now.minute(), now.second());
}
// format date/time
ostream& operator << (ostream& os, DateTime& dt) {
os << dt.year() << '/' << int(dt.month()) << '/' << int(dt.day()) << ' ';
os << int(dt.hour()) << ':' << setfill('0') << setw(2) << int(dt.minute());
os << ':' << setw(2) << int(dt.second()) << setfill(' ');
return os;
}
#endif // USE_DS1307
//------------------------------------------------------------------------------
void setup() {
Serial.begin(9600);
// pstr stores strings in flash to save RAM
cout << endl << pstr("FreeRam: ") << FreeRam() << endl;
#if WAIT_TO_START
cout << pstr("Type any character to start\n");
while (!Serial.available());
#endif // WAIT_TO_START
#if USE_DS1307
// connect to RTC
Wire.begin();
if (!RTC.begin()) error("RTC failed");
// set date time callback function
SdFile::dateTimeCallback(dateTime);
DateTime now = RTC.now();
cout << now << endl;
#endif // USE_DS1307
// initialize the SD card at SPI_HALF_SPEED to avoid bus errors with
// breadboards. use SPI_FULL_SPEED for better performance.
// if SD chip select is not SS, the second argument to init is CS pin number
if (!sd.init(SPI_HALF_SPEED)) sd.initErrorHalt();
// create a new file in root, the current working directory
char name[] = "LOGGER00.CSV";
for (uint8_t i = 0; i < 100; i++) {
name[6] = i/10 + '0';
name[7] = i%10 + '0';
if (sd.exists(name)) continue;
logfile.open(name);
break;
}
if (!logfile.is_open()) error("file.open");
cout << pstr("Logging to: ") << name << endl;
//format header in buffer
obufstream bout(buf, sizeof(buf));
bout << pstr("millis");
#if USE_DS1307
bout << pstr(",date time");
#endif USE_DS1307
for (uint8_t i = 0; i < SENSOR_COUNT; i++) {
bout << pstr(",sens") << int(i);
}
logfile << buf << endl;
#if ECHO_TO_SERIAL
cout << buf << endl;
#endif // ECHO_TO_SERIAL
}
//------------------------------------------------------------------------------
void loop() {
uint32_t m;
// wait for time to be a multiple of interval
do {
m = millis();
} while(m % LOG_INTERVAL);
// use buffer stream to format line
obufstream bout(buf, sizeof(buf));
// start with time in millis
bout << m;
#if USE_DS1307
DateTime now = RTC.now();
bout << ',' << now;
#endif
// read analog pins and format data
for (uint8_t ia = 0; ia < SENSOR_COUNT; ia++) {
#if ADC_DELAY
analogRead(ia);
delay(ADC_DELAY);
#endif // ADC_DELAY
bout << ',' << analogRead(ia);
}
bout << endl;
// log data
logfile << buf;
// flush data to SD
logfile.flush();
// check for error
if (!logfile) error("write data failed");
#if ECHO_TO_SERIAL
cout << buf;
#endif // ECHO_TO_SERIAL
// don't log two points in the same millis
if (m == millis()) delay(1);
}