I’ve been amassing a small army of broken arduinos over the past two months, but now I have something to show for it - the bones of a working (but altogether bulky) GPS tracker. The code I used seems kind of nasty to me, mostly because the bit-banging used for serial communication to try to ensure no data is missed in transition. The Arduino IDE is okay I guess (for a Java app), but if you like Ruby you may want to check out RAD. Looks like RAD only works with version 10 of the arduino SDK right now though.

In terms of kit hooked up, we’ve got an EM-406A (GPS Module) & an Arduino Mini along with a USB to serial header. I need to buy a EEPROM for storage, or possibly some kind of microSD reader. Borrowing some code from here we can parse NMEA to take a look at where you are with Google Maps.

\
\#define bit4800Delay 200 //1 bit per 0.2 ms\
\#define halfBit4800Delay 100

byte rx = 8; //Connect to EM-406A’s TX\
byte tx = 9; //Connect to EM-406A’s RX\
char dataformat[7] = “\$GPGGA”; //GGA\
char messageline[80] = “”;\
int i = 0;\
char latitude[10];\
char longitude[11];

void setup() {\
 pinMode(rx,INPUT);\
 pinMode(tx,OUTPUT);\
 digitalWrite(tx,HIGH); // Needs to be pulled high before the EM-406A
will return data\
 digitalWrite(13,HIGH); // Debugging LED\
 Serial.begin(9600); // Echo EM-406A output through serial\
}

char SWread()\
{\
 byte val = 0;\
 //Wait for start bit (0)\
 while(digitalRead(rx)  HIGH); 

  if (digitalRead(rx)  LOW) {\
 delayMicroseconds(halfBit4800Delay);

for (int offset = 0; offset \< 8; offset**) {\
 delayMicroseconds;\
 val |= digitalRead \<\< offset;\
 }
\
 delayMicroseconds;
\
 // Bitbanging\
 if\
 return val-128;\
 else\
 return val;\
 }\
}
\
void char2string {\
 i = 0;\
 messageline[0] = SWread;\
 if {\
 i**;\
 messageline[i] = SWread();

while(messageline[i] != 13 & i\<80) {\
 i++;\
 messageline[i] = SWread();\
 }

messageline[i+1] = ‘\0;\
 }\
}

void loop() {\
 char2string();\
 if (strncmp(messageline, dataformat, 6) == 0 & i\>4) {\
 Serial.println(messageline);\
 }\
}\