This info may help some new people wanting to use a GPS breakout board on a Mega.
Physically, it should work with many of the generic GPS breakout boards that have 4 pins (VCC,RX,TX,GND).
This example uses the Adafruit 'parsing.pde' sketch.
There are other GPS libraries with example code too. I have not tested them yet.
See TinyGPS and Tiny GPS ++
http://arduiniana.org/libraries/tinygps/
http://arduiniana.org/libraries/tinygpsplus/
I wanted to test the Adafruit Ultimate GPS Shield board on my Mega in a raw way.
Basically, just like you would connect a generic GPS breakout board lying on desk.
Found some errors in the example GPS sketches written by Adafruit
First, I switched the shields onboard switch to 'Soft Serial'.
Then I hooked wires directly to the shields TX and RX solder pads.
TX on GPS shield to RX1 (pin 19) on Mega
RX on GPS shield to TX1 (pin 18) on Mega
5v on shield to 5v on Mega
GND on shield to GND on Mega
This 'emulates' a simple 4 connector generic GPS board hookup to the hardware serial pins on the Mega.
You are ready to use the modified Adafruit parsing sketch or whatever.
Side info on using the Mega as a 'dumb 'USB GPS puck':
Hook GPS board RX to RX0 (Digital pin 0) and TX to TX0 (Digital pin 1).
The arrows printed on these Mega pins hint at this 'backwards' connection.
Load a blank sketch on the Mega, then just look at the raw data coming from TX0/RX0 that passes out the USB cable with any serial monitor set to the right baud rate. The Ada GPS are 9600. Other GPS boards might be set at 4800.
Set a mapping (or other) program to the correct COM port and baud rate, and you will normally get NMEA position data streaming in. Some GPS chips output UBX and NMEA etc. This can cause problems with the software you are using to read the data (or not).
Now back to the Adafruit 'parsing.pde' example sketch.
It was missing a line to enable hardware serial properly.
Don't waste your time with the 'echo' sketch or the 'leo_echo' sketch.
Same comment and code errors exist in them.
Hopefully they will go back over the sketches and correct them (including comments!)
My sketch is set to use hardware serial with the 'normal' wiring described above.
Code works perfectly for me (finally!)
PS - I'm going to be testing a few other bare GPS modules with hardware serial on the Mega.
Will report back here with what I find out.
Enjoy!
// Test code for Adafruit GPS modules/shields 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. -ada
//
// Added verbosity and corrections by PhantomYoYo in A.D. 2014 ;)
/******************* CONSTANTS AND VARIABLES *******************
****************************************************************/
#include <Adafruit_GPS.h>
#include <SoftwareSerial.h>
// If you're using a bare GPS module:
// Connect the GPS Power pin to 5V
// Connect the GPS Ground pin to ground
// Then wire for software serial (sketch example default):
// Connect the GPS TX (transmit) pin to Digital 3
// Connect the GPS RX (receive) pin to Digital 2
// Or wire for hardware serial (e.g. Arduino Mega):
// Connect the GPS TX (transmit) pin to Arduino RX1, RX2 or RX3
// Connect the GPS RX (receive) pin to matching TX1, TX2 or TX3
// If you're using the Adafruit GPS shield, change
// SoftwareSerial mySerial(3, 2); -> SoftwareSerial mySerial(8, 7);
// and make sure the switch is set to SoftSerial
// This shield is *not* capable of software serial on a Mega!
// Instead add 2 jumper wires:
// Connect jumper from TX pad to Arduino RX1, RX2 or RX3
// Connect jumper from RX pad to Arduino TX1, TX2 or TX3
// To use software serial, keep these two lines enabled
// (you can change the pin numbers to match your wiring):
//SoftwareSerial mySerial(3, 2);
//Adafruit_GPS GPS(&mySerial);
//
// To use hardware serial (e.g. Arduino Mega), comment
// out the above two lines and enable these two lines instead:
HardwareSerial mySerial = Serial1;
Adafruit_GPS GPS(&Serial1);
// 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
// this keeps track of whether we're using the interrupt
// off by default!
boolean usingInterrupt = false;
void useInterrupt(boolean); // Func prototype keeps Arduino 0023 happy
/************************ ARDUINO SETUP ***********************
****************************************************************/
void setup()
{
// connect at 115200 so we can read the GPS fast enough and echo without dropping chars
// also spit it out
// make sure your Serial Monitor is set to 115200 to see data visually
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
// Request updates on antenna status, comment out to keep quiet
GPS.sendCommand(PGCMD_ANTENNA);
// 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);
// Ask for firmware version
mySerial.println(PMTK_Q_RELEASE);
}
// 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!
#ifdef UDR0
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.
#endif
}
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;
}
}
uint32_t timer = millis();
/******************** MAIN LOOP ********************************
****************************************************************/
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) Serial.print(c);
}
// 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 trying 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
}
// if millis() or timer wraps around, we'll just reset it
if (timer > millis()) timer = millis();
// 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((int)GPS.fix);
Serial.print(" quality: "); Serial.println((int)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((int)GPS.satellites);
}
}
}