HELP GPS Module

GPS NEO-6M-0-001 - HCMODU0023 module with active antenna

Pin connections

Module - Arduino
GND    -     GND
RX       -  Pin 11
TX     -  Pin 10
VCC    -    3.3V

Output is via UART, 9600 baud 8/none/1. Format is NMEA

	$ ADDR ,VALUES *CHECKSUM CRLF

ADDR is GPxxx xxx = msg format
,VALUES are ‘,’ separated values
*CHECKSUM (no prior ‘,’) is Hex exclusive OR $ to *

Latitude and longitude

Latitude or Longitude min.decmin

e.g. Lat 5204.82093 = 52deg 04.82093min

e.g. Long 00120.77221 = 1deg 20.77221min

Typical module output and message formats

NMEA sentences

$Address ,[value] ... *[checksum]

$GPRMC fields are

Field
1 UTC hhmmss.ss
2 A|V status
3 Lat ddmm.mmmm
4 N|S
5 Lon dddmm.mmmm
6 E|W
7 SOG knots
8 COG deg T
9 Date ddmmyy
+ some others

$GPVTG fields are

Field
1 True Track
2 T
3 Magnetic track
4 M
5 Ground Speed, knots
6 N
7 GroundSpeed, Km/h
8 K

$GPGGA fields are

Field
1 Time UTC
2 Latitude
3 NS
4 Longitude
5 EW
6 Fix quality 0 - invalid, 1 = GPS fix, 2-9 other
7 No of satellits tracked
8 Horix dilution
9 Altitude metres ASL
10 Height geoid abbove WSG84 metres
+ others

$GPGSV fields are satellite positions and data

$GPGLL fields are
1 Latitude
2 NS
3 Longitude
4 EW
5 Time
6 AV active or void

Code for 128 x 64 LCD display using U8glib LCD library

#include "SoftwareSerial.h"
#include "U8glib.h"

// GPS 11 RX, 10 TX
SoftwareSerial gps(10, 11);

// LCD 6 SCK(E), 5 MOSI(RW), 4 SS(RS)
U8GLIB_ST7920_128X64_1X lcd(6, 5, 4);

void setup()
{
    gps.begin(9600); // start GPS serial
}
void loop()
{
  char gpsbuf[200]; // GPS output line
  char pbuf[20]; // extract and printed buffer
  
  do
  {  
    getline(gpsbuf);
  } while(strncmp(gpsbuf, "$GPRMC", 6) != 0);
      
   lcd.firstPage();
   do
   {
     lcd.setFont(u8g_font_helvR08);
     
     // 1st line
     lcd.drawStr(2, 8, "Latitude");            
     lcd.drawStr(66, 8, "Longitude");
     // Lat
     extfmt(3, "** ****", gpsbuf, pbuf);
     lcd.drawStr(2, 19, pbuf);
     // NS 
     extfmt(4, "*", gpsbuf, pbuf);
     lcd.drawStr(40, 19, pbuf);
     // Lon
     extfmt(5, "*** ****", gpsbuf, pbuf);
     lcd.drawStr(66, 19, pbuf);
     // EW 
     extfmt(6, "*", gpsbuf, pbuf);
     lcd.drawStr(110, 19, pbuf);
     
     // 2nd line
     lcd.drawStr(2, 40, "Time");
     lcd.drawStr(66, 40, "Date");
     // Time
     extfmt(1, "**:**", gpsbuf, pbuf);
     lcd.drawStr(2, 51, pbuf);
     // Date 
     extfmt(9, "**-**-**", gpsbuf, pbuf);
     lcd.drawStr(66, 51, pbuf);        
   } while(lcd.nextPage());   
}

// get a line from the GPS
void getline(char *buf)
{
  int bp = 0;
  char c;
  
  do
  {
    c = gps.read(); // -1 if no char available
    if(c == -1) continue;
    buf[bp++] = c;
  } while(c != '\n');
  buf[bp] = '\0';
}

// find field, extract in fmt from inbuf to outbuf
// fmt * = copy inbuf to outbuf, else copy fmt to outbuf
void extfmt(int field, char *fmt, char *inbuf, char *outbuf)
{
  int f = 0; // field count and char pointers
  int fp = 0;
  int ip = 0;
  int op = 0;
   
  // find field and ip start
  while(f != field)
  {
    while(inbuf[ip++] != ',');
    f++;
  }
  
  // format from ip
    while(fmt[fp] !='\0')
    {      
      if(fmt[fp] == '*') outbuf[op] = inbuf[ip++]; // outbuf = inbuf
      else outbuf[op] = fmt[fp]; // outbuf = fmt
      fp++;
      op++;
    }
  outbuf[op] = '\0'; // add end of string
}