Odometer

#include <Wire.h>
#include "SSD1306Ascii.h"
#include "SSD1306AsciiWire.h"

#include <NMEAGPS.h>
#include <SoftwareSerial.h>
//#include <NeoSWSerial.h>


#define I2C_ADDRESS 0x3C
#define RST_PIN -1
SSD1306AsciiWire lcd;

NMEAGPS               gps;
float                 odometer;
NeoGPS::Location_t    lastLoc;
bool                  lastLocOK = false;
//NeoSWSerial           gpsPort(2, 3);
static const int RXPin = 0, TXPin = 1;
static const uint32_t GPSBaud = 9600;
SoftwareSerial gpsPort(RXPin, TXPin);

const int SHOW_INTERVAL = 1; // 12;
const int INITIAL_SHOW  = (2 * SHOW_INTERVAL) - 1; // works for any SHOW_INTERVAL
      int show          = INITIAL_SHOW;

const int   BUZZER_PIN  = 4;
const float SPEED_LIMIT = 0.1; //55.0; // kph


void setup()
{
  Serial.begin(9600);
  gpsPort.begin(GPSBaud);

  Wire.begin();
  lcd.begin(&Adafruit128x64, I2C_ADDRESS);
  lcd.setFont(System5x7);
  lcd.clear();
  lcd.println(" ");
  lcd.println("GPS DATA LOGGER");

  delay(3000);
  lcd.clear();

} // setup()


void loop()
{
  // Parse any available GPS characters
  if (gps.available( gpsPort )) {

    //  Enough GPS characters have been parsed to produce a fix structure.
    //     This happens exactly once per second.
    gps_fix fix = gps.read();  // get all the GPS fields
    show = (show + 1) % SHOW_INTERVAL;

    // Check the speed
    if (fix.valid.speed && (fix.speed_kph() > SPEED_LIMIT)) {
      digitalWrite( BUZZER_PIN, HIGH );
      Serial.println( F("Too fast!") );
    } else {
      digitalWrite( BUZZER_PIN, LOW );
    }

    // Update the odometer
    if (fix.valid.location) { // && fix.valid.speed && (fix.speed_kph() > MIN_SPEED)
      if (lastLocOK) {
        odometer += fix.location.DistanceKm( lastLoc );
      }

      // ...and save this location for next time
      lastLoc   = fix.location;
      lastLocOK = true;
    }

    // Update the LCD (oled)
    if (show == 0) {

      #define MAX_CHARS 20
      char displayBufffer[MAX_CHARS];

      // usando un buffer di dimensione fissa displayBufffer, la lunghezza del testo sarà sempre uguale
      // es:  Odometer = 256.5 sarà stampato sul display il testo "Odometer: 256.50 Km"
      // es:  Odometer = 26.0 sarà stampato sul display il testo  "Odometer:  26.00 Km"

      // Per ulteriori chiarimenti ti rimando alla documentazione C++ per l'istruzione snprintf
      snprintf(displayBufffer, MAX_CHARS, "Odometer: % 3d.%02d Km", (int)odometer, (int)(odometer * 100)%100);
      lcd.print(displayBufffer);
    }

    // Print out a few things.  DON'T PRINT TOO MUCH!
    Serial.print( F("LAT=") );
    if (fix.valid.location)
      Serial.print( fix.latitude(), 6);
    Serial.print( F(" LON=") );
    if (fix.valid.location)
      Serial.print( fix.longitude(), 6);
    Serial.print( F(" SAT=") );
    if (fix.valid.satellites)
      Serial.print( fix.satellites );
    Serial.print( F(" Speed=") );
    if (fix.valid.speed)
      Serial.print( fix.speed_kph() );

    Serial.print( F(" ODO=") );
    Serial.print( odometer );
    Serial.print( F(" km") );
    Serial.println();
  }

  // Make sure *something* is being received!
  if ((show == INITIAL_SHOW) && (millis() > 5000)) {
    if (gps.statistics.chars == 0) {
      Serial.println( F("** No characters received from GPS: check wiring **") );
    } else {
      Serial.println( F("** Characters are being received from GPS, but no valid data was parsed: check baud rate. **") );
    }

    lcd.clear();
    lcd.println(F("No data from GPS"));
    lcd.println(F("(Timeout 5s)"));
  }

}