PA6H/MT3339 GPS: how to know if time is GPS locked or from internal RTC?

Projects Programming
29

Hi, /dev.

I can't use serial.print, because the device has a stand alone atmega328p.
I've tried this. It shows in sequence:

stato: RTC

data/ora:
577224377.24

speed: 0.00

#include <NMEAGPS.h> // Using Neo-GPS lib
#include <EEPROM.h>
#include <NeoSWSerial.h> //Serial com
#include <LiquidCrystal.h>
LiquidCrystal lcd(8, 9, 4, 12, 13, 7); // RS, EN, D4, D5, D6, D7
static const int RXPin = A5, TXPin = 6;

NeoSWSerial gpsSerial(RXPin, TXPin);
NMEAGPS gps;
gps_fix fix;

// #define gpsPort Serial1 // you may be using a different serial port
int contr=0; // Correzione manuale al contrasto automatico (-10...+10)
String stato;
int dataOraA;
int dataOraB;
unsigned long t1=0;
byte n=0;

void setup()
{
  Serial.begin( 9600 );
  // Serial.println( F("status,date/time,speed") );
  // gpsPort.begin( 9600 );
  gpsSerial.begin(9600);        //Starting GPS at a 9600 baud rate
  lcd.begin(16,2); 
  pinMode(11, OUTPUT);// PWM out per contrasto automatico
  if(EEPROM.read(0)==255) contr=70; else contr=EEPROM.read(13); // Carica il valore del contrasto
  analogWrite(11,contr); // Applica il contrasto memorizzato
}

extern void detectRTCtimeOnly();
  
void loop()
{
  if (gps.available( gpsSerial ))
  {
    fix = gps.read();
    detectRTCtimeOnly();

    if (fix.valid.status)
      {      
      if (fix.status < gps_fix::STATUS_TIME_ONLY)
        stato="RTC";
      else if (fix.status == gps_fix::STATUS_TIME_ONLY) 
        stato="GPS";
      else stato=String(fix.status); // 3 or above 
      }
    else stato='-';  
    
    if (fix.valid.date || fix.valid.time) 
    {
      Serial << fix.dateTime;
      dataOraA= fix.dateTime;
      dataOraB= fix.dateTime_cs;
      
      Serial.print( '.' );
      if (fix.dateTime_cs < 10)
        Serial.print( '0' );
      Serial.print( fix.dateTime_cs );
    }
    Serial.print( ',' );
    
    if (fix.valid.speed)
      Serial.print( fix.speed_kph() );
    Serial.println();
  }

if(millis()-t1>999)
  {
  t1=millis();
  n+=1; if(n>3) n=1;
  stampa();
  }
}

void stampa()
{
lcd.clear();
if(n==1)
  {
  lcd.print(F("stato: "));
  lcd.print(stato);
  }
else if(n==2)
  {
  lcd.print(F("data/ora: "));
  lcd.print(dataOraA);
  lcd.print('.');
  if (dataOraB<10) lcd.print('0');
  lcd.print(dataOraB);
  }  
else if(n==3)
  {
  lcd.print(F("speed: "));
  lcd.print(fix.speed_kph());
  }
}
  
void detectRTCtimeOnly()
{
  if (fix.valid.status && (fix.status == gps_fix::STATUS_TIME_ONLY)) {
    // The MTK3339 will never send this value,
    //   but this is how you might detect it on ublox GPS devices.
    return;
  }

  bool noSatellites = not fix.valid.satellites or (fix.satellites == 0);
  bool haveTime     = fix.valid.date or fix.valid.time;
  bool tracking     = fix.valid.status and (fix.status >= gps_fix::STATUS_STD);

  if (not tracking) {
    // Look for tracked satellites from the GSV sentences
    for (uint8_t i=0; i < gps.sat_count; i++) {
      if (gps.satellites[ i ].tracked) {
        tracking = true;
        break;
      }
    }
  }

  if (haveTime and tracking and noSatellites) {
    // Force the fix status even though no NMEA sentences set it
    fix.valid.status = true;
    fix.status       = gps_fix::STATUS_TIME_ONLY;
  }

} // detectRTCtimeOnly

Every 3 seconds data/ora increases by 3.
"GPS" doesn't appear.