Parsing works with RMC & GGA with a nice example as well

Adafruit_GPS.cpp

@@ -12,6 +12,8 @@ All text above must be included in any redistribution
 
 #include <Adafruit_GPS.h>
 
+// how long are max NMEA lines to parse?
+#define MAXLINELENGTH 120
 
 // we double buffer: read one line in and leave one for the main program
 volatile char line1[MAXLINELENGTH];
@@ -25,13 +27,27 @@ volatile boolean recvdflag;
 
 
 boolean Adafruit_GPS::parse(char *nmea) {
+  // do checksum check
+
+  // first look if we even have one
+  if (nmea[strlen(nmea)-4] == '*') {
+    uint16_t sum = parseHex(nmea[strlen(nmea)-3]) * 16;
+    sum += parseHex(nmea[strlen(nmea)-2]);
+    
+    // check checksum 
+    for (uint8_t i=1; i < (strlen(nmea)-4); i++) {
+      sum ^= nmea[i];
+    }
+    if (sum != 0) {
+      // bad checksum :(
+      //return false;
+    }
+  }
 
   // look for a few common sentences
-
   if (strstr(nmea, "$GPGGA")) {
     // found GGA
     char *p = nmea;
-
     // get time
     p = strchr(p, ',')+1;
     float timef = atof(p);
@@ -41,7 +57,6 @@ boolean Adafruit_GPS::parse(char *nmea) {
     seconds = (time % 100);
 
     milliseconds = fmod(timef, 1.0) * 1000;
-    p = strchr(p, ',')+1;
 
     // parse out latitude
     p = strchr(p, ',')+1;
@@ -80,7 +95,7 @@ boolean Adafruit_GPS::parse(char *nmea) {
     return true;
   }
   if (strstr(nmea, "$GPRMC")) {
-    // found RMC
+   // found RMC
     char *p = nmea;
 
     // get time
@@ -94,6 +109,7 @@ boolean Adafruit_GPS::parse(char *nmea) {
     milliseconds = fmod(timef, 1.0) * 1000;
 
     p = strchr(p, ',')+1;
+    // Serial.println(p);
     if (p[0] == 'A') 
       fix = true;
     else if (p[0] == 'V')
@@ -142,13 +158,15 @@ boolean Adafruit_GPS::parse(char *nmea) {
   return false;
 }
 
-void Adafruit_GPS::read(void) {
+char Adafruit_GPS::read(void) {
+  char c = 0;
+  
   if (paused)
-    return;
+    return c;
 
 
   if (gpsSwSerial->available()) {
-    char c = gpsSwSerial->read();
+    c = gpsSwSerial->read();
 
     //Serial.print(c);
 
@@ -166,37 +184,32 @@ void Adafruit_GPS::read(void) {
         currentline = line1;
         lastline = line2;
       }
-      /*
+      
-      Serial.println("----");
-      Serial.println((char *)lastline);
-      Serial.println("----");
-      */
-      // do checksum check
 
-      // first look if we even have one
+      //Serial.println("----");
-      if (lastline[lineidx-4] == '*') {
+      //Serial.println((char *)lastline);
-	uint16_t sum = parseHex(lastline[lineidx-3]) * 16;
+      //Serial.println("----");
-	sum += parseHex(lastline[lineidx-2]);
-	
-	// check checksum 
-	for (uint8_t i=1; i < (lineidx-4); i++) {
-	  sum ^= lastline[i];
-	}
-	if (sum == 0) {
-	  recvdflag = true;
-	}
-      }
       lineidx = 0;
- 
+      recvdflag = true;
     }
+    
     currentline[lineidx++] = c;
     if (lineidx >= MAXLINELENGTH)
       lineidx = MAXLINELENGTH-1;
   }
+  return c;
 }
 
-Adafruit_GPS::Adafruit_GPS(void) {
+// Constructor when using SoftwareSerial or NewSoftSerial
+#if ARDUINO >= 100
+Adafruit_GPS::Adafruit_GPS(SoftwareSerial *ser) {
+#else
+  Adafruit_GPS::Adafruit_GPS(NewSoftSerial *ser) {
+#endif
+
   common_init();  // Set everything to common state, then...
+  gpsSwSerial = ser; // ...override swSerial with value passed.
+
   recvdflag = false;
   paused = false;
   lineidx = 0;
@@ -211,17 +224,9 @@ Adafruit_GPS::Adafruit_GPS(void) {
   fixquality = satellites = 0;
 }
 
-// Constructor when using SoftwareSerial or NewSoftSerial
+
-#if ARDUINO >= 100
+void Adafruit_GPS::begin(uint16_t baud) 
-void Adafruit_GPS::begin(SoftwareSerial *ser, uint16_t baud) 
-#else
-void Adafruit_GPS::begin(NewSoftSerial *ser, uint16_t baud) 
-#endif
 {
-  gpsSwSerial = ser; // ...override swSerial with value passed.
-
-
-  // 9600 NMEA is the default baud rate
   gpsSwSerial->begin(baud);
 }
 

Adafruit_GPS.h

@@ -40,19 +40,17 @@ All text above must be included in any redistribution
  #include "NewSoftSerial.h"
 #endif
 
-// how long are max NMEA lines to parse?
-#define MAXLINELENGTH 100
 
 class Adafruit_GPS {
  public:
-  Adafruit_GPS(void); // Constructor when using SoftwareSerial
+  void begin(uint16_t baud); 
 
 #if ARDUINO >= 100
-  void begin(SoftwareSerial *ser, uint16_t baud); // Constructor when using SoftwareSerial
+  Adafruit_GPS(SoftwareSerial *ser); // Constructor when using SoftwareSerial
 #else
-  void begin(NewSoftSerial  *ser, uint16_t baud); // Constructor when using NewSoftSerial
+  Adafruit_GPS(NewSoftSerial  *ser); // Constructor when using NewSoftSerial
 #endif
-  void begin(HardwareSerial *ser, uint16_t baud); // Constructor when using HardwareSerial
+  Adafruit_GPS(HardwareSerial *ser); // Constructor when using HardwareSerial
 
   char *lastNMEA(void);
   boolean newNMEAreceived();
@@ -63,7 +61,7 @@ class Adafruit_GPS {
   boolean parseNMEA(char *response);
   uint8_t parseHex(char c);
 
-  void read(void);
+  char read(void);
   boolean parse(char *);
   void interruptReads(boolean r);
 

examples/parsing/parsing.pde

@@ -0,0 +1,150 @@
+// Test code for Adafruit GPS modules using MTK3329/MTK3339 driver
+//
+// This code shows how to listen to the GPS module in an interrupt
+// which allows the program to have more 'freedom' - just parse
+// when a new NMEA sentence is available! Then access data when
+// desired.
+//
+// Tested and works great with the Adafruit Ultimate GPS module
+// using MTK33x9 chipset
+//    ------> http://www.adafruit.com/products/746
+// Pick one up today at the Adafruit electronics shop 
+// and help support open source hardware & software! -ada
+
+#include <Adafruit_GPS.h>
+
+// these are for Arduino 1.0
+#include <SoftwareSerial.h>
+SoftwareSerial mySerial(3, 2);
+
+// if using Arduino v23 or earlier, uncomment these
+// two lines and comment out the above. You will
+// need to install NewSoftSerial
+//  #include <NewSoftSerial.h>
+//  NewSoftSerial mySerial(3, 2);
+
+// Set GPSECHO to 'false' to turn off echoing the GPS data to the Serial console
+// Set to 'true' if you want to debug and listen to the raw GPS sentences
+#define GPSECHO  true
+
+// Connect the GPS Power pin to 5V
+// Connect the GPS Ground pin to ground
+// Connect the GPS TX (transmit) pin to Digital 3
+// Connect the GPS RX (receive) pin to Digital 2
+Adafruit_GPS GPS(&mySerial);
+
+
+// this keeps track of whether we're using the interrupt
+// off by default!
+boolean usingInterrupt = false;
+
+void setup()  
+{
+    
+  // connect at 115200 so we can read the GPS fast enough and echo without dropping chars
+  // also spit it out
+  Serial.begin(115200);
+  Serial.println("Adafruit GPS library basic test!");
+
+  // 9600 NMEA is the default baud rate for Adafruit MTK GPS's- some use 4800
+  GPS.begin(9600);
+  
+  // uncomment this line to turn on RMC (recommended minimum) and GGA (fix data) including altitude
+  GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCGGA);
+  // uncomment this line to turn on only the "minimum recommended" data
+  //GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCONLY);
+  // For parsing data, we don't suggest using anything but either RMC only or RMC+GGA since
+  // the parser doesn't care about other sentences at this time
+  
+  // Set the update rate
+  GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ);   // 1 Hz update rate
+  // For the parsing code to work nicely and have time to sort thru the data, and
+  // print it out we don't suggest using anything higher than 1 Hz
+
+  // the nice thing about this code is you can have a timer0 interrupt go off
+  // every 1 millisecond, and read data from the GPS for you. that makes the
+  // loop code a heck of a lot easier!
+  useInterrupt(true);
+
+  delay(1000);
+}
+
+
+// Interrupt is called once a millisecond, looks for any new GPS data, and stores it
+SIGNAL(TIMER0_COMPA_vect) {
+  char c = GPS.read();
+  // if you want to debug, this is a good time to do it!
+  if (GPSECHO)
+    if (c) UDR0 = c;  
+    // writing direct to UDR0 is much much faster than Serial.print 
+    // but only one character can be written at a time. 
+}
+
+void useInterrupt(boolean v) {
+  if (v) {
+    // Timer0 is already used for millis() - we'll just interrupt somewhere
+    // in the middle and call the "Compare A" function above
+    OCR0A = 0xAF;
+    TIMSK0 |= _BV(OCIE0A);
+    usingInterrupt = true;
+  } else {
+    // do not call the interrupt function COMPA anymore
+    TIMSK0 &= ~_BV(OCIE0A);
+    usingInterrupt = false;
+  }
+}
+
+uint16_t timer = millis();
+void loop()                     // run over and over again
+{
+  // in case you are not using the interrupt above, you'll
+  // need to 'hand query' the GPS, not suggested :(
+  if (! usingInterrupt) {
+    // read data from the GPS in the 'main loop'
+    char c = GPS.read();
+    // if you want to debug, this is a good time to do it!
+    if (GPSECHO)
+      if (c) UDR0 = c;
+      // writing direct to UDR0 is much much faster than Serial.print 
+      // but only one character can be written at a time. 
+  }
+  
+  // if a sentence is received, we can check the checksum, parse it...
+  if (GPS.newNMEAreceived()) {
+    // a tricky thing here is if we print the NMEA sentence, or data
+    // we end up not listening and catching other sentences! 
+    // so be very wary if using OUTPUT_ALLDATA and trytng to print out data
+    //Serial.println(GPS.lastNMEA());   // this also sets the newNMEAreceived() flag to false
+  
+    if (!GPS.parse(GPS.lastNMEA()))   // this also sets the newNMEAreceived() flag to false
+      return;  // we can fail to parse a sentence in which case we should just wait for another
+  }
+  
+  // approximately every 2 seconds or so, print out the current stats
+  if (millis() - timer > 2000) { 
+    timer = millis(); // reset the timer
+    
+    Serial.print("\nTime: ");
+    Serial.print(GPS.hour, DEC); Serial.print(':');
+    Serial.print(GPS.minute, DEC); Serial.print(':');
+    Serial.print(GPS.seconds, DEC); Serial.print('.');
+    Serial.println(GPS.milliseconds);
+    Serial.print("Date: ");
+    Serial.print(GPS.day, DEC); Serial.print('/');
+    Serial.print(GPS.month, DEC); Serial.print("/20");
+    Serial.println(GPS.year, DEC);
+    Serial.print("Fix: "); Serial.print(GPS.fix);
+    Serial.print(" quality: "); Serial.println(GPS.fixquality); 
+    if (GPS.fix) {
+      Serial.print("Location: ");
+      Serial.print(GPS.latitude, 4); Serial.print(GPS.lat);
+      Serial.print(", "); 
+      Serial.print(GPS.longitude, 4); Serial.println(GPS.lon);
+      
+      Serial.print("Speed (knots): "); Serial.println(GPS.speed);
+      Serial.print("Angle: "); Serial.println(GPS.angle);
+      Serial.print("Altitude: "); Serial.println(GPS.altitude);
+      Serial.print("Satellites: "); Serial.println(GPS.satellites);
+    }
+  }
+}