Pressure Temperature Logger for Arduino Data Shield

PressureLogger.ino

#include <SD.h>
#include <Wire.h>
#include "RTClib.h"

// Data logger for temperature and pressure data using the Adafruit
// logger shield.  

// Logging Interval (milliseconds)
#define LOG_INTERVAL 60000

// Write Interval (milliseconds).  How often to write data to the SD card
// Writing every time would be better and prevent any data loss, but this 
// will use much less power.  Power is indeed a concern for this setup
#define WRITE_INTERVAL 600000
uint32_t syncTime =0;

// Echo to serial settings.  Turn on (1) for daignostics, but turn off (0)
// before deploying to save power.
#define SERIAL_DIAG 1

// Pin definitions - where we have things connected
#define PressurePin 0
#define TempPin 1
#define ChipSel 10
#define BANDGAPREF 14            // special indicator that we want to measure the bandgap
#define aref_voltage 5.0         // Analog voltage reference
#define bandgap_voltage 1.1      // this is not super guaranteed but its not -too- off

RTC_DS1307 RTC; 

// Setup the logging file
File logfile;

void error(char *str)
{
  Serial.print("error: ");
  Serial.println(str);
  while(1);
}

void setup(void)
{
  Serial.begin(9600);
  Serial.println();

  // Initalize the SD Card (or try anyway)
  Serial.print("Initializing SD card...");
  pinMode(ChipSel, OUTPUT);
  
  if (!SD.begin(ChipSel)) {
    error("Card failed, or not present");
  }
  Serial.println("card initialized.");
  
  // Create the logging file 
  // Change the file name here!
  char filename[] = "PressureLogger.CSV";
  for (uint8_t i = 0; i < 100; i++) {
    filename[6] = i/10 + '0';
    filename[7] = i%10 + '0';
    if (! SD.exists(filename)) {
      // only open a new file if it doesn't exist
      logfile = SD.open(filename, FILE_WRITE); 
      break;  // leave the loop!
    }
  }
  
  if (! logfile) {
    error("couldnt create file");
  }
  
  Serial.print("Logging to: ");
  Serial.println(filename);

  // connect to RTC
  Wire.begin();  
  if (!RTC.begin()) {
    logfile.println("RTC failed");
#if SERIAL_DIAG
    Serial.println("RTC failed");
#endif  //ECHO_TO_SERIAL
  }
  
logfile.println("Millis,Stamp,DateTime,Pres,Temp,Vcc");    
#if ECHO_TO_SERIAL
  Serial.println("Millis,Stamp,DateTime,Pres,Temp,Vcc");
#endif //ECHO_TO_SERIAL
 
  // If you want to set the aref to something other than 5v, use this.  Docs online.
  //analogReference(EXTERNAL);
}


// This is the main loop
void loop(void)
{
  DateTime now;

  // delay for the amount of time we want between readings
  delay((LOG_INTERVAL -1) - (millis() % LOG_INTERVAL));
  
  // log milliseconds since starting
  uint32_t m = millis();
  logfile.print(m);           // milliseconds since start
  logfile.print(", ");    
#if SERIAL_DIAG
  Serial.print(m);         // milliseconds since start
  Serial.print(", ");  
#endif

  // Get time from the RTC
  now = RTC.now();
  // log time
  logfile.print(now.unixtime()); // seconds since 1/1/1970
  logfile.print(", ");
  logfile.print('"');
  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);
  logfile.print('"');
#if SERIAL_DIAG
  Serial.print(now.unixtime()); // seconds since 1/1/1970
  Serial.print(", ");
  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);
  Serial.print('"');
#endif //ECHO_TO_SERIAL

  analogRead(PressurePin);
  delay(10); 
  int PressureReading = analogRead(PressurePin);  
  
  analogRead(TempPin); 
  delay(10);
  int tempReading = analogRead(TempPin);    
  
  // converting that reading to voltage, for 3.3v arduino use 3.3, for 5.0, use 5.0
  float voltage = tempReading * aref_voltage / 1024;  
  float temperatureC = (voltage - 0.5) * 100 ;
  float temperatureF = (temperatureC * 9 / 5) + 32;
  
  logfile.print(", ");    
  logfile.print(PressureReading);
  logfile.print(", ");    
  logfile.print(temperatureF);
#if SERIAL_DIAG
  Serial.print(", ");   
  Serial.print(PressureReading);
  Serial.print(", ");    
  Serial.print(temperatureF);
#endif //ECHO_TO_SERIAL

  // Log the estimated 'VCC' voltage by measuring the internal 1.1v ref
  analogRead(BANDGAPREF); 
  delay(10);
  int refReading = analogRead(BANDGAPREF); 
  float supplyvoltage = (bandgap_voltage * 1024) / refReading; 
  
  logfile.print(", ");
  logfile.print(supplyvoltage);
#if SERIAL_DIAG
  Serial.print(", ");   
  Serial.print(supplyvoltage);
#endif // ECHO_TO_SERIAL

  logfile.println();
#if SERIAL_DIAG
  Serial.println();
#endif // ECHO_TO_SERIAL

  // Dump data to the disk.  This is power hungry
  if ((millis() - syncTime) < WRITE_INTERVAL) return;
  syncTime = millis();
  logfile.flush();
}