NMEAorder.ino

#include <NMEAGPS.h>

//======================================================================
//  Program: NMEAorder.ino
//
//  Description:  This example program records the order of sentences 
//    received in each 1-second interval.  The last sentence is 
//    important to know, as that will be used to determine when the 
//    GPS quiet time is starting (see NMEA.ino).  It is safe to perform
//    time-consuming operations at that point, and the risk of losing
//    characters will be minimized (see comments in 'GPSloop').
//
//  Prerequisites:
//     1) Your GPS device has been correctly powered.
//          Be careful when connecting 3.3V devices.
//     2) Your GPS device is correctly connected to an Arduino serial port.
//          See GPSport.h for the default connections.
//     3) You know the default baud rate of your GPS device
//          Use NMEAdiagnostic.ino to scan for the correct baud rate.
//     4) NMEAGPS_RECOGNIZE_ALL must be enabled in NMEAGPS_cfg.h
//
//  'Serial' is for debug output to the Serial Monitor window.
//
//  License:
//    Copyright (C) 2014-2017, SlashDevin
//
//    This file is part of NeoGPS
//
//    NeoGPS is free software: you can redistribute it and/or modify
//    it under the terms of the GNU General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    (at your option) any later version.
//
//    NeoGPS is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU General Public License for more details.
//
//    You should have received a copy of the GNU General Public License
//    along with NeoGPS.  If not, see <http://www.gnu.org/licenses/>.
//
//======================================================================

#include <GPSport.h>
  
//------------------------------------------------------------
// Check configuration

#ifndef NMEAGPS_RECOGNIZE_ALL
  #error You must define NMEAGPS_RECOGNIZE_ALL in NMEAGPS_cfg.h!
#endif

#ifdef NMEAGPS_INTERRUPT_PROCESSING
  #error You must *NOT* define NMEAGPS_INTERRUPT_PROCESSING in NMEAGPS_cfg.h!
#endif

static NMEAGPS  gps         ; // This parses received characters
static uint32_t last_rx = 0L; // The last millis() time a character was
                              // received from GPS.  This is used to
                              // determine when the GPS quiet time begins.

//------------------------------------------------------------

static NMEAGPS::nmea_msg_t last_sentence_in_interval = NMEAGPS::NMEA_UNKNOWN;
static       uint8_t       prev_sentence_count       = 0;
static       uint8_t       sentence_count            = 0;
static const uint8_t       MAX_SENTENCES             = 20; // per second
static NMEAGPS::nmea_msg_t sentences[ MAX_SENTENCES ];

static void recordSentenceTypes()
{
  // Always save the last sentence, even if we're full
  sentences[ sentence_count ] = gps.nmeaMessage;
  if (sentence_count < MAX_SENTENCES-1)
    sentence_count++;
  
} // recordSentenceTypes

//-----------------------------------------------------------  

static void printSentenceOrder()
{
  DEBUG_PORT.println( F("\nSentence order in each 1-second interval:") );

  for (uint8_t i=0; i<sentence_count; i++) {
    DEBUG_PORT.print( F("  ") );
    DEBUG_PORT.println( gps.string_for( sentences[i] ) );
  }

  if (sentences[sentence_count-1] == LAST_SENTENCE_IN_INTERVAL) {
    DEBUG_PORT.print( F("\nSUCCESS: LAST_SENTENCE_IN_INTERVAL is correctly set to NMEAGPS::NMEA_") );
  } else {
    DEBUG_PORT.print( F("\nERROR: LAST_SENTENCE_IN_INTERVAL is incorrectly set to NMEAGPS::NMEA_") );
    DEBUG_PORT.print( gps.string_for( LAST_SENTENCE_IN_INTERVAL ) );
    DEBUG_PORT.print( F("!\n  You must change this line in NMEAGPS_cfg.h:\n"
                          "     #define LAST_SENTENCE_IN_INTERVAL NMEAGPS::NMEA_") );
  }
  DEBUG_PORT.println( gps.string_for( sentences[sentence_count-1] ) );
  DEBUG_PORT.println();

} // printSentenceOrder

//------------------------------------

static void GPSloop()
{  
  while (gpsPort.available()) {
    last_rx = millis();

    if (gps.decode( gpsPort.read() ) == NMEAGPS::DECODE_COMPLETED) {

      if (last_sentence_in_interval == NMEAGPS::NMEA_UNKNOWN) {
        // Still building the list
        recordSentenceTypes();
        DEBUG_PORT.print( '.' );
      }
    }
  }
} // GPSloop

//----------------------------------------------------------------
//  Determine whether the GPS quiet time has started.
//
//  This is only needed in the example programs, which must work 
//  for *any* GPS device.
//
//  It also "pretends" to have a quiet time once per 
//  second so that some debug messages are emitted.  This allows 
//  beginners to see whether the GPS device is correctly 
//  connected and functioning.

static bool quietTimeStarted()
{
  uint32_t current_ms       = millis();
  uint32_t ms_since_last_rx = current_ms - last_rx;

  if (ms_since_last_rx > 5) {

    // The GPS device has not sent any characters for at least 5ms.
    //   See if we've been getting chars sometime during the last second.
    //   If not, the GPS may not be working or connected properly.

           bool     getting_chars   = (ms_since_last_rx < 1000UL);
    static uint32_t last_quiet_time = 0UL;
           bool     just_went_quiet =
                            (((int32_t) (last_rx - last_quiet_time)) > 10L);
           bool     next_quiet_time =
                               ((current_ms - last_quiet_time) >= 1000UL);

    if ((getting_chars && just_went_quiet)
          ||
        (!getting_chars && next_quiet_time)) {

      last_quiet_time = current_ms;  // Remember for next loop

      //  If we're not getting good data, make some suggestions.
      
      bool allDone = false;

      if (!getting_chars) {
        
        DEBUG_PORT.println( F("\nCheck GPS device and/or connections.  No characters received.\n") );
        
        allDone = true;

      } else if (sentence_count == 0) {
        
        DEBUG_PORT.println( F("No valid sentences, but characters are being received.\n"
        "Check baud rate or device protocol configuration.\n" ) );

        allDone = true;
      }

      if (allDone) {
        DEBUG_PORT.print( F("\nEND.\n") );
        for (;;)
          ; // hang!
      }

      // No problem, just a real GPS quiet time.
      return true;
    }
  }

  return false;
  
} // quietTimeStarted

//----------------------------------------------------------------
//  Figure out what sentence the GPS device sends 
//  as the last sentence in each 1-second interval.

static void watchForLastSentence()
{
  if (quietTimeStarted()) {

    if (prev_sentence_count != sentence_count) {
    
      // We have NOT received two full intervals of sentences with
      //    the same number of sentences in each interval.  Start
      //    recording again.
      prev_sentence_count = sentence_count;
      sentence_count      = 0;
      
    } else if (sentence_count > 0) {

      // Got it!
      last_sentence_in_interval = sentences[ sentence_count-1 ];
    }
  }

} // watchForLastSentence

//--------------------------

void setup()
{
  DEBUG_PORT.begin(9600);
  while (!DEBUG_PORT)
    ;

  DEBUG_PORT.print( F("NMEAorder.INO: started\n") );
  DEBUG_PORT.print( F("fix object size = ") );
  DEBUG_PORT.println( sizeof(gps.fix()) );
  DEBUG_PORT.print( F("NMEAGPS object size = ") );
  DEBUG_PORT.println( sizeof(gps) );
  DEBUG_PORT.println( F("Looking for GPS device on " GPS_PORT_NAME) );
  DEBUG_PORT.flush();
  
  gpsPort.begin( 9600 );
}

//--------------------------

void loop()
{
  GPSloop();

  if (last_sentence_in_interval == NMEAGPS::NMEA_UNKNOWN)
    watchForLastSentence();
  else {

    printSentenceOrder();
    for (;;)
      ; // All done!
  }
}