GPS is navisys GM401R. The GPS module connects to power, ground, Tx, and Rx. I found this code online:
/*
Example code for connecting a Parallax GPS module to the Arduino
Igor Gonzalez Martin. 05-04-2007
igor.gonzalez.martin@gmail.com
English translation by djmatic 19-05-2007
Listen for the $GPRMC string and extract the GPS location data from this.
Display the result in the Arduino's serial monitor.
*/
#include <string.h>
#include <ctype.h>
int ledPin = 13; // LED test pin
int rxPin = 0; // RX PIN
int txPin = 1; // TX TX
int byteGPS=-1;
char linea[300] = "";
char comandoGPR[7] = "$GPRMC";
int cont=0;
int bien=0;
int conta=0;
int indices[13];
void setup() {
pinMode(ledPin, OUTPUT); // Initialize LED pin
pinMode(rxPin, INPUT);
pinMode(txPin, OUTPUT);
Serial.begin(4800);
for (int i=0;i<300;i++){ // Initialize a buffer for received data
linea[i]=' ';
}
}
void loop() {
digitalWrite(ledPin, HIGH);
byteGPS=Serial.read(); // Read a byte of the serial port
if (byteGPS == -1) { // See if the port is empty yet
delay(100);
} else {
// note: there is a potential buffer overflow here!
linea[conta]=byteGPS; // If there is serial port data, it is put in the buffer
conta++;
Serial.print(byteGPS, BYTE);
if (byteGPS==13){ // If the received byte is = to 13, end of transmission
// note: the actual end of transmission is <CR><LF> (i.e. 0x13 0x10)
digitalWrite(ledPin, LOW);
cont=0;
bien=0;
// The following for loop starts at 1, because this code is clowny and the first byte is the <LF> (0x10) from the previous transmission.
for (int i=1;i<7;i++){ // Verifies if the received command starts with $GPR
if (linea[i]==comandoGPR[i-1]){
bien++;
}
}
if(bien==6){ // If yes, continue and process the data
for (int i=0;i<300;i++){
if (linea[i]==','){ // check for the position of the "," separator
// note: again, there is a potential buffer overflow here!
indices[cont]=i;
cont++;
}
if (linea[i]=='*'){ // ... and the "*"
indices[12]=i;
cont++;
}
}
Serial.println(""); // ... and write to the serial port
Serial.println("");
Serial.println("---------------");
for (int i=0;i<12;i++){
switch(i){
case 0 :Serial.print("Time in UTC (HhMmSs): ");break;
case 1 :Serial.print("Status (A=OK,V=KO): ");break;
case 2 :Serial.print("Latitude: ");break;
case 3 :Serial.print("Direction (N/S): ");break;
case 4 :Serial.print("Longitude: ");break;
case 5 :Serial.print("Direction (E/W): ");break;
case 6 :Serial.print("Velocity in knots: ");break;
case 7 :Serial.print("Heading in degrees: ");break;
case 8 :Serial.print("Date UTC (DdMmAa): ");break;
case 9 :Serial.print("Magnetic degrees: ");break;
case 10 :Serial.print("(E/W): ");break;
case 11 :Serial.print("Mode: ");break;
case 12 :Serial.print("Checksum: ");break;
}
for (int j=indices[i];j<(indices[i+1]-1);j++){
Serial.print(linea[j+1]);
}
Serial.println("");
}
Serial.println("---------------");
}
conta=0; // Reset the buffer
for (int i=0;i<300;i++){ //
linea[i]=' ';
}
}
}
}
The above works to print the correct GPS string to the serial port like this:
"$GPRMC,154655,A,4428.1874,N,00440.5185,W,000.7,000.0,050407,,,A*6C"
However, as you can see it seems never to reach anything within the "bien == 6" condition block (the switch statement). This is fine, as I don't actually need the stuff in the switch statement (it's just there to make the data easier to understand) as long as the data is correct (which it seems to be). I just need this to print the same data to an SD card situated in an adafruit data logger shield. Typically, I would do this by simply changing the "Serial" to "myFile" for the print statements which print the data I need. The problem is I am having trouble actually finding where the data is coming from. Clearly the GPS is printing accurate GPS coordinates, but I can't tell where in the code it's actually happening, and it's making me feel really inept. If it matters, I am using an Arduino Due. Am I missing something painfully simple?