Sparkfun Venus GPS and Arduino

I've just been playing with the Sparkfun Venus GPS module.

Very neat! It comes with more interfaces than you can shake a stick at, see the spec on the Sparkfun page. But I decided to use good old serial (or to be accurate the Software Serial library on the Arduino), so I just attached header pins to the RX0, TX0, 3.3V and GND connections and pushed it into some breadboard.

Upload the following sketch to your Arduino BEFORE making any connections. 5V from an IO pin left high on the Arduino may well kill the 3.3V output from the Tx pin on the GPS module.

#include <SoftwareSerial.h>

SoftwareSerial gpsSerial(10, 11); // RX, TX (TX not used)

const int sentenceSize = 80;

char sentence[sentenceSize];

void setup()

{

  Serial.begin(9600);

  gpsSerial.begin(9600);

}

void loop()

{

  static int i = 0;

  if (gpsSerial.available())

  {

    char ch = gpsSerial.read();

    if (ch != '\n' && i < sentenceSize)

    {

      sentence[i] = ch;

      i++;

    }

    else

    {

     sentence[i] = '\0';

     i = 0;

     displayGPS();

    }

  }

}

void displayGPS()

{

  char field[20];

  getField(field, 0);

  if (strcmp(field, "$GPRMC") == 0)

  {

    Serial.print("Lat: ");

    getField(field, 3);  // number

    Serial.print(field);

    getField(field, 4); // N/S

    Serial.print(field);

    

    Serial.print(" Long: ");

    getField(field, 5);  // number

    Serial.print(field);

    getField(field, 6);  // E/W

    Serial.println(field);

  }

}

void getField(char* buffer, int index)

{

  int sentencePos = 0;

  int fieldPos = 0;

  int commaCount = 0;

  while (sentencePos < sentenceSize)

  {

    if (sentence[sentencePos] == ',')

    {

      commaCount ++;

      sentencePos ++;

    }

    if (commaCount == index)

    {

      buffer[fieldPos] = sentence[sentencePos];

      fieldPos ++;

    }

    sentencePos ++;

  }

  buffer[fieldPos] = '\0';

} 

Make the following connections

• The red lead goes from 3.3V Arduino to 3.3V GPS Module
• The blue lead, GND to GND
• The yellow lead Arduino Pin 10 to TX0 on the GPS Module

Open the Serial Monitor and view your position!

There is a really useful resource here, on the Arduino Playground, that tells you all about the various fields that your GPS unit is sending.