esp32_Adafruit_GPS/examples/GPS_HardwareSerial_Timing/GPS_HardwareSerial_Timing.ino

// Test code for Ultimate GPS Using Hardware Serial (e.g. GPS Flora or FeatherWing)
//
// This code is similar to GPS_HardwareSerial_Parsing, except for the additional 
// elements to keep track of how long it has been since time and fix data have been 
// received. This approach lets you keep an up to date clock based on GPS time at 
// any time in between GPS fixes.
//
// This code shows how to listen to the GPS module via polling. Best used with
// Feathers or Flora where you have hardware Serial and no interrupt
//
// Tested and works great with the Adafruit GPS FeatherWing
// ------> https://www.adafruit.com/products/3133
// or Flora GPS
// ------> https://www.adafruit.com/products/1059
// but also works with the shield, breakout
// ------> https://www.adafruit.com/products/1272
// ------> https://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>

// what's the name of the hardware serial port?
#define GPSSerial Serial1

// Connect to the GPS on the hardware port
Adafruit_GPS GPS(&GPSSerial);

// 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

uint32_t timer = millis();


void setup()
{
  //while (!Serial);  // uncomment to have the sketch wait until Serial is ready

  // 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 (uncomment the one you want.)
  //GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ); // 1 Hz update rate
  //GPS.sendCommand(PMTK_SET_NMEA_UPDATE_200_MILLIHERTZ); // 5 second update time
  GPS.sendCommand(PMTK_SET_NMEA_UPDATE_100_MILLIHERTZ); // 10 second update time
  // 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);

  delay(1000);

  // Ask for firmware version
  GPSSerial.println(PMTK_Q_RELEASE);
}

void loop() // run over and over again
{
  // 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 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
  }
  // if millis() or timer wraps around, we'll just reset it
  if (timer > millis()) timer = millis();

  // approximately every 2 seconds or so, random intervals, print out the current stats
  static unsigned nextInterval = 2000;
  if (millis() - timer > nextInterval) {
    timer = millis(); // reset the timer
    nextInterval = 1500 + random(1000);
    // Time in seconds keeps increasing after we get the NMEA sentence.
    // This estimate will lag real time due to transmission and parsing delays,
    // but the lag should be small and should also be consistent.
    float s = GPS.seconds + GPS.milliseconds/1000. + GPS.secondsSinceTime(); 
    int m = GPS.minute;
    int h = GPS.hour;
    int d = GPS.day;
    // Adjust time and day forward to account for elapsed time.
    // This will break at month boundaries!!! Humans will have to cope with April 31,32 etc.
    while(s > 60){ s -= 60; m++; }    
    while(m > 60){ m -= 60; h++; }
    while(h > 24){ h -= 24; d++; }
    // ISO Standard Date Format, with leading zeros https://xkcd.com/1179/ 
    Serial.print("\nDate: ");  
    Serial.print(GPS.year+2000, DEC); Serial.print("-");
    if(GPS.month < 10) Serial.print("0");
    Serial.print(GPS.month, DEC); Serial.print("-");
    if(d < 10) Serial.print("0");
    Serial.print(d, DEC);
    Serial.print("   Time: ");
    if(h < 10) Serial.print("0");
    Serial.print(h, DEC); Serial.print(':');
    if(m < 10) Serial.print("0");
    Serial.print(m, DEC); Serial.print(':');
    if(s < 10) Serial.print("0");
    Serial.println(s, 3);
    Serial.print("Fix: "); Serial.print((int)GPS.fix);
    Serial.print(" quality: "); Serial.println((int)GPS.fixquality);
    Serial.print("Times [s] since last fix: "); Serial.print(GPS.secondsSinceFix(),3); 
    Serial.print(",  GPS time: "); Serial.print(GPS.secondsSinceTime(),3); 
    Serial.print(",  GPS date: "); Serial.println(GPS.secondsSinceDate(),3); 
    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);
    }
  }
}