C++ Arduino Project with Ublox NEO6MV2 GPS and HMC5883L Compass

Question

I want to use GPS module and compass sensor together and log the info with SD Card. I finished the hardware part but my code doesn't work as it must be. I can log GPS data on SD card but I cannot log GPS data with Compass' heading data in this format => date-time+longtitude+lattitude+speed+heading..

I think for some reason, the loop is breaking and it stops after first run but I couldn't find out why.

#include <SoftwareSerial.h>
#include <TinyGPS.h>
#include <SD.h>
#include <Wire.h>
#include <HMC5883L.h>

HMC5883L compass;

TinyGPS gps;
static char dtostrfbuffer[20];
int CS = 10;
int LED = 13;
int SD_LED = A0;
int GPS_LED = A1;
int Blink_LED = 6;
SoftwareSerial mySerial(2 , 3); // RX, TX


String SD_date_time = "";
String SD_lat = "";
String SD_lon = "";
String SD_spd = "";
String SD_heading = "";
String dataString ="";

static void gpsdump(TinyGPS &gps);
static bool feedgps();


void setup()
{
  pinMode(CS, OUTPUT);  //Chip Select Pin for the SD Card
  pinMode(LED, OUTPUT);  //LED Indicator

  //Serial interfaces
  Serial.begin(9600);
  mySerial.begin(9600);
   Wire.begin();

  //Connect to the SD Card
  if(!SD.begin(CS))
  {
    Serial.println("card failure");
    return;
  }


 compass = HMC5883L(); //new instance of HMC5883L library
 setupHMC5883L(); //setup the HMC5883L

}


void loop()
{
  bool newdata = false;
  unsigned long start = millis();

  // Every 5 second we print an update
  while (millis() - start < 5000)
  {
    if (feedgps())
      newdata = true;
  }
  gpsdump(gps);
  int intHead = ReadCompass();
  SD_heading = String(intHead); 
  dataString = SD_date_time + "," + SD_lat + "," + SD_lon + "," + SD_spd + "," + SD_heading;

  //Open the Data CSV File
  File dataFile = SD.open("LOG.csv", FILE_WRITE);
  if (dataFile)
  {
    dataFile.println(dataString);
    Serial.print("SD card writing:");
    Serial.println(dataString);
    dataFile.close();
    digitalWrite(SD_LED, HIGH);      //if sd works led is on

  }
  else
  {
    Serial.println("\ncouldn't open LOG file!");
  }
}


int ReadCompass() 
{
  int intHead;
  // Retrive the raw values from the compass (not scaled).
  MagnetometerRaw raw = compass.ReadRawAxis();
  // Retrived the scaled values from the compass (scaled to the configured scale).
  MagnetometerScaled scaled = compass.ReadScaledAxis();

  // Values are accessed like so:
  int MilliGauss_OnThe_XAxis = scaled.XAxis;// (or YAxis, or ZAxis)

  // Calculate heading when the magnetometer is level, then correct for signs of axis.
  float heading = atan2(scaled.YAxis, scaled.XAxis);
  // Correct for when signs are reversed.
  if(heading < 0)
    heading += 2*PI;

  // Check for wrap due to addition of declination.
  if(heading > 2*PI)
    heading -= 2*PI;

  // Convert radians to degrees for readability.
  float headingDegrees = heading * 180/M_PI; 

  intHead= int (headingDegrees);
  return intHead;
  delay (200);
}

//GPS Reading Function  
static void gpsdump(TinyGPS &gps)
{
  float flat, flon;
  unsigned long age, date, time, chars = 0;
  unsigned short sentences = 0, failed = 0;

  int year;
  byte month, day, hour, minute, second, hundredths;


  gps.f_get_position(&flat, &flon, &age); 
  gps.crack_datetime(&year, &month, &day, &hour, &minute, &second, &hundredths, &age);
  gps.stats(&chars, &sentences, &failed);
  float fmps = gps.f_speed_mps(); // speed in m/sec

  if (age == TinyGPS::GPS_INVALID_AGE)
  {
    Serial.println("no GPS connection");

    SD_lat = "invalid";
    SD_lon = "invalid";
    SD_date_time = "invalid";

    Serial.print("Age:"); 
    Serial.println(age);
    Serial.print("char count:"); 
    Serial.println(chars);
    Serial.print("valid NMEA sentences"); 
    Serial.println(sentences);
    Serial.print("invalid NMEA sentences"); 
    Serial.println(failed);
    digitalWrite(GPS_LED, HIGH);                //if GPS doesn't get fix led is on
  }
  else
  {

    Serial.println("GPS connection is available ");

    digitalWrite(LED, HIGH);          //GPS fix exists

    SD_lat = dtostrf(flat,9,5,dtostrfbuffer);
    SD_lon = dtostrf(flon,10,5,dtostrfbuffer);
    SD_spd = dtostrf(fmps,5,2,dtostrfbuffer);

    char sz[32];
    sprintf(sz, "%02d/%02d/%02d %02d:%02d:%02d   ",
    day, month, year, hour+2, minute, second);
    Serial.print(sz);
    Serial.println(SD_lat);
    Serial.println(SD_lon);
    Serial.print("Hiz:"); 
    Serial.println(SD_spd);
    Serial.print("Age:"); 
    Serial.println(age);
    Serial.print("char count:"); 
    Serial.println(chars);
    Serial.print("valid NMEA sentences"); 
    Serial.println(sentences);
    Serial.print("invalid NMEA sentences:"); 
    Serial.println(failed);
    SD_date_time = sz;
  }
  Serial.println();
}

static bool feedgps()
{
  while (mySerial.available())
  {
    if (gps.encode(mySerial.read()))
      return true;
  }
  return false;
}


void setupHMC5883L(){
 //Setup the HMC5883L, and check for errors
 int error; 
 error = compass.SetScale(1.3); //Set the scale of the compass.
 if(error != 0) Serial.println(compass.GetErrorText(error)); //check if there is an error, and print if so

 error = compass.SetMeasurementMode(Measurement_Continuous); // Set the measurement mode to Continuous
 if(error != 0) Serial.println(compass.GetErrorText(error)); //check if there is an error, and print if so
}

Answer 1

Some things to ask.. Do you continue to print debug messages?

When you say you can log GPS data maybe you mean that when you add the code to read the compass things quit working, as in you record nothing usable. Is that true?

I had trouble in a project where I tried to use software serial and the normal serial port at the same time. If there is traffic on both serial ports at the same time, the software port timing can be disturbed. Maybe this is getting you too.

Float precision is not really very good for Lat/Lon values, might not be a problem for you but the precision step size could be 2 or 3 feet. I would look at logging the NMEA data for Lat/Lon as strings, unmodified. Let the application reading the log file parse the string where it might have doubles to store with.

Note that using double on an arduino is the same as float, you don't get more precision by using the double type there, its really just a 4 byte float.

Answer 2

I solved the problem. RAM of Arduino UNO (ATmega328) is not enough for the code above. I closed all things about serial monitor, so I cannot observe the logged data but SD, Compass and GPS works fine right now. thanks.