GPS logging on SD card using TinyGPS

Question

I'm a beginner in Arduino world and I want to create a simple SD datalogger that works with GPS (module NEO-6M) and light sensor. I know there are a number of tutorials on GPS logging including:

Create a GPS Data Logger Using The Arduino (Bob Cravens)
Geo Data Logger: Arduino+GPS+SD+Accelerometer (Instructables)
Making a SD card GPS logger with Arduino and MTK3329 GPS module (Arduinodev)

but my problem is that those tutorials are either too complex (i.e. include extra stuff like displays) or they don't use TinyGPS or TinyGPS++ library. In the first step I've managed to get GPS working and displaying the result on my laptop screen (via Serial.print()) using example code from TinyGPS library. In the next step I managed to use tutorial for Adafruit Data Logger to log data on SD card. The problem: light sensor logs ok, but for GPS it only logs a strings of 99.999999. Tried various tweaks but so far not sure what I got wrong. I use Arduino Uno, NEO-6M GPS, Catalex MicroSD Card Adapter, simple LDR. Here is my current code:

    #include <TinyGPS++.h>
    #include <SoftwareSerial.h>
    #include "SD.h"

    //input for the light detecting sensor (LDR)
    int LDR = A3;   

    //inputs and triggers for GPS
    TinyGPSPlus gps;
    SoftwareSerial ss (7, 8); // TX=7, RX=8 

    // digital pin 4 for the SD cs line
    const int chipSelect = 4;
    File logfile;// the logging file

    //data logger timing and other 
    #define LOG_INTERVAL  1000 // mills between entries
    #define SYNC_INTERVAL 1000 // mills between calls to flush() - to write data to the card
    uint32_t syncTime = 0; // time of last sync()
    #define ECHO_TO_SERIAL   1 // echo data to serial port
    #define WAIT_TO_START    0 // Wait for serial input in setup()    

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

      #if WAIT_TO_START
        Serial.println("Type any character to start");
        while (!Serial.available());
      #endif //WAIT_TO_START

      // initialize the SD card
      Serial.print("Initializing SD card...");

      pinMode(10, OUTPUT);

      // see if the card is present and can be initialized:
      if (!SD.begin(chipSelect)) {
        Serial.println("Card failed, or not present");
        // don't do anything more:
        return;
      }
      Serial.println("card initialized.");

      // create a new file
      char filename[] = "LOGGER00.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!
        }
      }

      Serial.print("Logging to: ");
      Serial.println(filename);

      logfile.println("date,time,lat,long,light");

      #if ECHO_TO_SERIAL
        Serial.println("lat,log,date,time,altitude,light");
      #endif// attempt to write out the header to the file
    }

void loop(void) {  

   // delay for the amount of time we want between readings
   delay((LOG_INTERVAL -1) - (millis() % LOG_INTERVAL));

   //here is GPS data (if I got it right)
   while (ss.available() > 0)
   gps.encode(ss.read());
   logfile.print(gps.date.value());
   logfile.print(", ");
   logfile.print(gps.time.value());
   logfile.print(", ");
   logfile.print(gps.location.lat(), 6);
   logfile.print(", ");
   logfile.print(gps.location.lng(), 6);
   logfile.print(", ");
   #if ECHO_TO_SERIAL
      Serial.print(gps.date.value());
      Serial.print(", ");  
      Serial.print(gps.time.value());
      Serial.print(", ");  
      Serial.print(gps.location.lat(), 6);
      Serial.print(", ");  
      Serial.print(gps.location.lng(), 6);
      Serial.print(", ");  
   #endif

   //Read light intensity
   float lux = 500/(10.72/(5-(photocellReading * 0.00488759))*(photocellReading * 0.00488759));
   logfile.println(lux);
   #if ECHO_TO_SERIAL
      Serial.println(lux);
   #endif //ECHO_TO_SERIAL

   //write data to disk
   if ((millis() - syncTime) < SYNC_INTERVAL) return;
   syncTime = millis();
   logfile.flush();
}

GPS logging on SD card using TinyGPS

0 Answers0