Comprensione di NeoGPS domande su AltSoftSerial SoftwareSerial.h- fix- fix.valid

Ciao sto studiando il codice della libreria Neo GPS sono un autodidatta e piano piano con un po’ di libri e un po’ di pratica sto imparando.

Ho tre domande.


1 Domanda

Perchè vengono caricate due librerie per la comunicazione seriale:

  • AltSoftSerial
  • SoftwareSerial.h

Studiando su internet ho capito che la prima permette la ricezione e comunicazione delle informazioni contemporaneamente mentre la seconda no ed è meno performante.
Ma il perchè ne vengano selezionate entrambe mi è oscuro.


2 Domanda

fix.valid è l’invocazione de metodo valid sull’oggetto fix?

Non riesco a capire il senso di questa procedura e i significati tecnici che ci sono dietro

 if (fix.valid.location)
      logFile.print(fix.longitude(), 6);
    logFile.print(',');
    if (fix.valid.location)
      logFile.print(fix.latitude(), 6);
    logFile.print(',');
    if (fix.valid.altitude)

** 3 Domanda**
Perchè vengono creati due oggetti distinti gps e fix?
Ho, forse, capito la necessità di inizializzare l’oggetto gps, ma non capisco fix

Perchè inizializziamo questi due oggetti e sono distinti?

NMEAGPS gps; // NeoGPS object to be used throughout
gps_fix fix; // The latest GPS information received from the gpsPort
#define GPS_BAUD 9600 // GPS module's default baud rate

e successivamente

while (gps.available( gpsPort )) {
    fix = gps.read();  // get the entire fix structure, once per second

    if (logGPSData()) { // Log the GPS data
      SerialMonitor.println( F("GPS logged.") ); // Print a debug message

Qui trovate il codice completo

#include <SPI.h>
#include <SdFat.h>
#include <NMEAGPS.h>
#include <Wire.h>
#define ARDUINO_USD_CS 10 // uSD card CS pin (pin 10 on SparkFun GPS Logger Shield)

/////////////////////////
// Log File Defintions //
/////////////////////////
// Keep in mind, the SD library has max file name lengths of 8.3 - 8 char prefix,
// and a 3 char suffix. 
char logFileName[13] = "gpslogXX.csv";
// Our log files are called "gpslogXX.csv, so "gpslog99.csv" is our max file.
#define MAX_LOG_FILES 100 // Number of log files that can be made

// Data to be logged:
#define LOG_COLUMN_HEADER \
  "longitude," "latitude," "altitude," "speed," "course," "date," "time," \
  "satellites," "Acc.X," "Acc.Y," "Acc.Z," "Gy.X," "Gy.Y," "Gy.Z," "Temp"
  // printed at the top of the file.

SdFat SD;
File  logFile;

/////////////////////////
// NeoGPS Definitions //
/////////////////////////
NMEAGPS gps; // NeoGPS object to be used throughout
gps_fix fix; // The latest GPS information received from the gpsPort
#define GPS_BAUD 9600 // GPS module's default baud rate







#include <SoftwareSerial.h>
#define ARDUINO_GPS_RX 9 // GPS TX, Arduino RX pin
#define ARDUINO_GPS_TX 8 // GPS RX, Arduino TX pin
SoftwareSerial ssGPS(ARDUINO_GPS_TX, ARDUINO_GPS_RX); 
/////////////////////////////////
// GPS Serial Port Definitions //
/////////////////////////////////
// If you're using a Mega, Leo or Due, use Serial1 for the GPS:
//#define gpsPort Serial1

// If you're using an Arduino Uno or other ATmega328 board that uses the
// 0/1 UART for programming/Serial monitor-ing, use AltSoftSerial:
#include <AltSoftSerial.h>
AltSoftSerial gpsPort; // Always on pins 8 & 9
//If you can't use pins 8 & 9, use this:
//#include <NeoSWSerial.h>
//NeoSWSerial gpsPort( 2, 3 ).

// Define the serial monitor port. On the Uno, Mega, and Leonardo this is 'Serial'
//  on other boards this may be 'SerialUSB'
#define SerialMonitor Serial

//#define USE_MPU
const int MPU=0x68;  // I2C address of the MPU-6050
int16_t AcX,AcY,AcZ,Tmp,GyX,GyY,GyZ;


void setup()
{
  Wire.begin();
  Wire.beginTransmission(MPU);
  Wire.write(0x6B);  // PWR_MGMT_1 register
  Wire.write(0);     // set to zero (wakes up the MPU-6050)
  Wire.endTransmission(true);

  SerialMonitor.begin(9600);
  gpsPort.begin(GPS_BAUD);

  SerialMonitor.println( F("Setting up SD card.") );

  updateFileName(); // Each time we start, create a new file, increment the number
  // see if the card is present and can be initialized:
  if (!SD.begin(ARDUINO_USD_CS))
  {
    SerialMonitor.println( F("Error initializing SD card.") );
  } else {
    logFile = SD.open( logFileName, FILE_WRITE );
    // Print a header at the top of the new file
    logFile.println( F(LOG_COLUMN_HEADER) );
  }

}

void loop()
{
  Wire.beginTransmission(MPU);
  Wire.write(0x3B);  // starting with register 0x3B (ACCEL_XOUT_H)
  Wire.endTransmission(false);
  Wire.requestFrom(MPU,14,true);  // request a total of 14 registers
  AcX=Wire.read()<<8|Wire.read();  // 0x3B (ACCEL_XOUT_H) & 0x3C (ACCEL_XOUT_L)     
  AcY=Wire.read()<<8|Wire.read();  // 0x3D (ACCEL_YOUT_H) & 0x3E (ACCEL_YOUT_L)
  AcZ=Wire.read()<<8|Wire.read();  // 0x3F (ACCEL_ZOUT_H) & 0x40 (ACCEL_ZOUT_L)
  Tmp=Wire.read()<<8|Wire.read();  // 0x41 (TEMP_OUT_H) & 0x42 (TEMP_OUT_L)
  GyX=Wire.read()<<8|Wire.read();  // 0x43 (GYRO_XOUT_H) & 0x44 (GYRO_XOUT_L)
  GyY=Wire.read()<<8|Wire.read();  // 0x45 (GYRO_YOUT_H) & 0x46 (GYRO_YOUT_L)
  GyZ=Wire.read()<<8|Wire.read();  // 0x47 (GYRO_ZOUT_H) & 0x48 (GYRO_ZOUT_L)

  while (gps.available( gpsPort )) {
    fix = gps.read();  // get the entire fix structure, once per second

    if (logGPSData()) { // Log the GPS data
      SerialMonitor.println( F("GPS logged.") ); // Print a debug message
    } else {// If we failed to log GPS
      // Print an error, don't update lastLog
      SerialMonitor.println( F("Failed to log new GPS data.") );
    }
  }
}


byte logGPSData()
{
  if (logFile.isOpen())
  { // Print longitude, latitude, altitude (in feet), speed (in mph), course
    // in (degrees), date, time, and number of satellites.

    if (fix.valid.location)
      logFile.print(fix.longitude(), 6);
    logFile.print(',');
    if (fix.valid.location)
      logFile.print(fix.latitude(), 6);
    logFile.print(',');
    if (fix.valid.altitude)
      logFile.print(fix.altitude() * 3.2808, 1);
    logFile.print(',');
    if (fix.valid.speed)
      logFile.print(fix.speed_mph(), 1);
    logFile.print(',');
    if (fix.valid.heading)
      logFile.print(fix.heading(), 1);
    logFile.print(',');

    if (fix.valid.date) {
      logFile.print( fix.dateTime.full_year() );
      if (fix.dateTime.month < 10)
        logFile.print( '0' );
      logFile.print( fix.dateTime.month );
      if (fix.dateTime.date < 10)
        logFile.print( '0' );
      logFile.print( fix.dateTime.date );
    }
    logFile.print(',');

    if (fix.valid.time) {
      if (fix.dateTime.hours < 10)
        logFile.print( '0' );
      logFile.print( fix.dateTime.hours );
      if (fix.dateTime.minutes < 10)
        logFile.print( '0' );
      logFile.print( fix.dateTime.minutes );
      if (fix.dateTime.seconds < 10)
        logFile.print( '0' );
      logFile.print( fix.dateTime.seconds );
    }
    logFile.print(',');

    if (fix.valid.satellites)
      logFile.print(fix.satellites);
    logFile.print(',');
    logFile.print(AcX);
    logFile.print(',');
    logFile.print(AcY);
    logFile.print(',');
    logFile.print(AcZ);
    logFile.print(',');
    logFile.print(GyX);
    logFile.print(',');
    logFile.print(GyY);
    logFile.print(',');
    logFile.print(GyZ);
    logFile.print(',');
    logFile.print(Tmp);
    logFile.println();
    logFile.flush(); // make sure the file contains at least this much

    return 1; // Return success
  }

  return 0; // If we failed to open the file, return fail
}

// updateFileName() - Looks through the log files already present on a card,
// and creates a new file with an incremented file index.
void updateFileName()
{
  for (uint8_t i; i < MAX_LOG_FILES; i++)
  {
    // Set logFileName to "gpslogXX.csv":
    logFileName[6] = (i/10) + '0';
    logFileName[7] = (i%10) + '0';

    if (!SD.exists(logFileName))
      break; // We found our index

    SerialMonitor.print(logFileName);
    SerialMonitor.println( F(" exists") );
  }
  SerialMonitor.print( F("File name: ") );
  SerialMonitor.println(logFileName);
}

Grazie mille per la disponibilità