I've tried this on both an Uno and a Mega. I tried switching between software serial and hardware serial in the code for each board, and also switched the shield between direct and softwareserial but nothing seems to work. I don't believe it's a wiring issue either, since it was working perfectly before and the board and shield are directly attached (no intermediate shields, etc).
I've included the echo code I'm using, but it's just the one included in the library.
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// Test code for Adafruit GPS modules using MTK3329/MTK3339 driver
//
// This code just echos whatever is coming from the GPS unit to the
// serial monitor, handy for debugging!
//
// 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>
#if ARDUINO >= 100
#include <SoftwareSerial.h>
#else
// Older Arduino IDE requires NewSoftSerial, download from:
// http://arduiniana.org/libraries/newsoftserial/
// #include <NewSoftSerial.h>
// DO NOT install NewSoftSerial if using Arduino 1.0 or later!
#endif
// Connect the GPS Power pin to 5V
// Connect the GPS Ground pin to ground
// If using software serial (sketch example default):
// Connect the GPS TX (transmit) pin to Digital 3
// Connect the GPS RX (receive) pin to Digital 2
// If using 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 using software serial, keep these lines enabled
// (you can change the pin numbers to match your wiring):
#if ARDUINO >= 100
SoftwareSerial mySerial(3, 2);
#else
NewSoftSerial mySerial(3, 2);
#endif
Adafruit_GPS GPS(&mySerial);
// If using hardware serial (e.g. Arduino Mega), comment
// out the above six lines and enable this line instead:
//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
void setup()
{
// connect at 115200 so we can read the GPS fast enuf and
// also spit it out
Serial.begin(115200);
Serial.println("Adafruit GPS library basic test!");
// 9600 NMEA is the default baud rate for MTK - some use 4800
GPS.begin(9600);
// You can adjust which sentences to have the module emit, below
// 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 for high update rates!
//GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCONLY);
// uncomment this line to turn on all the available data - for 9600 baud you'll want 1 Hz rate
//GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_ALLDATA);
// Set the update rate
// Note you must send both commands below to change both the output rate (how often the position
// is written to the serial line), and the position fix rate.
// 1 Hz update rate
//GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ);
//GPS.sendCommand(PMTK_API_SET_FIX_CTL_1HZ);
// 5 Hz update rate- for 9600 baud you'll have to set the output to RMC or RMCGGA only (see above)
GPS.sendCommand(PMTK_SET_NMEA_UPDATE_5HZ);
GPS.sendCommand(PMTK_API_SET_FIX_CTL_5HZ);
// 10 Hz update rate - for 9600 baud you'll have to set the output to RMC only (see above)
// Note the position can only be updated at most 5 times a second so it will lag behind serial output.
//GPS.sendCommand(PMTK_SET_NMEA_UPDATE_10HZ);
//GPS.sendCommand(PMTK_API_SET_FIX_CTL_5HZ);
// 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);
}
// 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;
}
}
void loop() // run over and over again
{
// do nothing! all reading and printing is done in the interrupt
}