Logs tilt meter and GPS data from a Jewell D700 tilt meter and Adafruit Ultimate GPS logger shield.

tilt_logger_system.ino

#include <SPI.h>
#include <Adafruit_GPS.h>
#include <SoftwareSerial.h>
#include <SD.h>
#include <avr/sleep.h>

// Make software serial port for GPS and GPS instance
SoftwareSerial mySerial(8, 7);
Adafruit_GPS GPS(&mySerial);

// Variables and defines
#define chipSelect 10
#define REDLED 3
#define GRNLED 4

int current_hour = 99;
boolean usingInterrupt = false;
boolean writeTilt = false;
boolean writeGPS = false;
void useInterrupt(boolean); // Func prototype keeps Arduino 0023 happy
char buffer[80];
char *stringptr;
uint8_t index = 0;

File logfile;

void error(uint8_t errno) {
 /*
 Blink out error codes based on an integer input.
 First making sure that all status LEDS are off.
 */

 digitalWrite(REDLED, LOW);
 digitalWrite(GRNLED, LOW);

 while(1) {
   uint8_t i;
   for (i=0; i < errno; i++) {
     digitalWrite(REDLED, HIGH);
     delay(100);
     digitalWrite(REDLED, LOW);
     delay(100);
   }
   for (i=errno; i<10; i++) {
     delay(200);
   }
 }
}

void setup() {
 /*
 Do the setup of the GPS, tilt meter, output pins, SD card, etc.
 This is where lots could go wrong if things are not hooked up correctly.
 */

 // Setup the LED pins and the CS pin for the SD card as output
 pinMode(REDLED, OUTPUT);
 pinMode(GRNLED, OUTPUT);
 pinMode(10, OUTPUT);

 // Turn on the LEDs to show that we are in setup
 digitalWrite(REDLED, HIGH);
 digitalWrite(GRNLED, HIGH);

 // see if the card is present and can be initialized:
 if (!SD.begin(chipSelect, 11, 12, 13)) {
   error(2);
 }

 // connect to the GPS at the desired rate
 GPS.begin(9600);
 GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCGGA);
 GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ);  
 GPS.sendCommand(PGCMD_NOANTENNA);
 useInterrupt(true);

 // Start and setup the tilt meter
 Serial.begin(9600);
 delay(1000);
 int bytesSent = Serial.write("*9900XY-SET-BAUDRATE,9600\n"); // Set baudrate on tilt meter
 delay(1000);
 bytesSent += Serial.write("*9900SO-XDR\n"); // Set to NMEA XDR format
 delay(1000);
 bytesSent += Serial.write("*9900XYC2\n"); // Set to 1 Hz output
 delay(2000);
 // DO ERROR CHECKING

 // Turn off the LEDs to show that we are done, blink them twice
 digitalWrite(REDLED, LOW);
 digitalWrite(GRNLED, LOW);

 for (int i=0; i < 2; i++) {
   delay(1000);
   digitalWrite(REDLED, HIGH);
   digitalWrite(GRNLED, HIGH);
   delay(1000);
   digitalWrite(REDLED, LOW);
   digitalWrite(GRNLED, LOW);
 }
}


// Interrupt is called once a millisecond, looks for any new GPS data, and stores it
SIGNAL(TIMER0_COMPA_vect) {
 char c = GPS.read();
}

void useInterrupt(boolean v) {
 if (v) {
   // Timer0 is already used for millis() - we'll just interrupt somewhere
   // in the middle and call the "Compare A" function above
   OCR0A = 0xAF;
   TIMSK0 |= _BV(OCIE0A);
   usingInterrupt = true;
 } 
 else {
   // do not call the interrupt function COMPA anymore
   TIMSK0 &= ~_BV(OCIE0A);
   usingInterrupt = false;
 }
}

void loop() {

  // Grab any serial from the GPS and store it
  if (GPS.newNMEAreceived()) {
    stringptr = GPS.lastNMEA();
    writeGPS = true;
  }

  // Grab any serial from the Tiltmeter and store it
  while (Serial.available() > 0) {
    if (index < 80) {
      char inChar = Serial.read();
      buffer[index] = inChar;
      index++;
      if (inChar == '\n'){
        writeTilt = true;
        index = 0;
      }
    }
  }
  
  // Process the GPS data if we can
  if (writeGPS) {
    GPS.parse(stringptr);
    // Check and deal with the need for a new logging file
    if (GPS.hour != current_hour){
      logfile.close();
      char name[13];
      getLogFileName(name,GPS.day,GPS.month,GPS.year,GPS.hour);

      // Prevent over-writing by adding to the sub-sequence set
      for (uint8_t i = 0; i < 10; i++) {
        name[7] = '0' + i;
        if (! SD.exists(name)) {
          break;
        }
      }

      // Open the new file and set the current hour to the new hour
      logfile = SD.open(name, FILE_WRITE);
      if( ! logfile ) {
        error(1);
      }
      current_hour = GPS.hour;
    }

    digitalWrite(REDLED, HIGH);
    uint8_t stringsize = strlen(stringptr);
    if (stringsize != logfile.write((uint8_t *)stringptr, stringsize))    //write the string to the SD file
      error(4);
    if (strstr(stringptr, "RMC") || strstr(stringptr, "GGA"))   
      logfile.flush();
    digitalWrite(REDLED, LOW);
    writeGPS = false;
  }
  
  // Log the tiltmeter data if we are ready
  if (writeTilt){
    digitalWrite(GRNLED, HIGH);
    //uint8_t stringsize = strlen(buffer);
    //if (stringsize != logfile.write((uint8_t *)stringptr, buffer))    //write the string to the SD file
    //  error(4);
    //if (strstr(stringptr, "XDR"))   
    //  logfile.flush();
    logfile.write(buffer);
    digitalWrite(GRNLED, LOW);
    writeTilt = false;
  }
}

char getLogFileName(char *filename, int day, int month, int year, int hour) {
/*
Format is DDDYYHHA.DAT
DDD - Day of year
YY  - Year
NN  - Logger unit number
A - Sub-sequence name, used if more than one file/day
*/
strcpy(filename, "");
strcpy(filename, "00000000.DAT");

// Get day of year and set it
int doy = calculateDayOfYear(day, month, year);

filename[0] = '0' + (doy/100)%100;
filename[1] = '0' + (doy/10)%10;
filename[2] = '0' + doy%10;

// Set the year
filename[3] = '0' + (year/10)%10;
filename[4] = '0' + year%10;

// Set the hour
filename[5] = '0' + (hour/10)%10;
filename[6] = '0' + hour%10;

}

int calculateDayOfYear(int day, int month, int year) {
 /*
 Given a day, month, and year (2 or 4 digit), returns
 the day of year. Errors return 999.
 */
 // List of days in a month for a normal year
 int daysInMonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};

 // Check if it is a leap year
 if (year%4  == 0)
 {
   daysInMonth[1] = 29;
 }

 // Make sure we are on a valid day of the month
 if (day < 1)
 {
   return 999;
 } else if (day > daysInMonth[month-1]) {
   return 999;
 }

 int doy = 0;
 for (int i = 0; i < month - 1; i++) {
   doy += daysInMonth[i];
 }

 doy += day;
 return doy;
}
/* End code */

/*
for( int i = 0; i < sizeof(data);  ++i )
   data[i] = (char)0;
to clear data
*/