Problema de codigo GPS

Buenas!

Estoy jugando con la placa GPS Logger de Adafruit y usando el codigo SDLog en la configuracion ALLDATA consigo leer por puerto Serial a cada segundo las lineas RMC y GGA pero en la tarjeta SD solo graba generalmente la GGA. Por necesidad necesito una alternancia de GGA RMC GGA... Aqui os pongo el codigo para ver si me podeis tirar una mano (seguro que es una tonteria).

#include <Adafruit_GPS.h>
#include <SoftwareSerial.h>
#include <SD.h>
#include <avr/sleep.h>
#include "GPSconfig.h"

// Ladyada's logger modified by Bill Greiman to use the SdFat library
//
// This code shows how to listen to the GPS module in an interrupt
// which allows the program to have more 'freedom' - just parse
// when a new NMEA sentence is available! Then access data when
// desired.
//
// Tested and works great with the Adafruit Ultimate GPS Shield
// using MTK33x9 chipset
//    ------> http://www.adafruit.com/products/
// Pick one up today at the Adafruit electronics shop 
// and help support open source hardware & software! -ada

SoftwareSerial mySerial(8, 7);
Adafruit_GPS GPS(&mySerial);

// 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
/* set to true to only log to SD when GPS has a fix, for debugging, keep it false */
#define LOG_FIXONLY false  

// Set the pins used
#define chipSelect 10
#define ledPin 13

File logfile;

// read a Hex value and return the decimal equivalent
uint8_t parseHex(char c) {
  if (c < '0')
    return 0;
  if (c <= '9')
    return c - '0';
  if (c < 'A')
    return 0;
  if (c <= 'F')
    return (c - 'A')+10;
}

// blink out an error code
void error(uint8_t errno) {
/*
  if (SD.errorCode()) {
    putstring("SD error: ");
    Serial.print(card.errorCode(), HEX);
    Serial.print(',');
    Serial.println(card.errorData(), HEX);
  }
  */
  while(1) {
    uint8_t i;
    for (i=0; i<errno; i++) {
      digitalWrite(ledPin, HIGH);
      delay(100);
      digitalWrite(ledPin, LOW);
      delay(100);
    }
    for (i=errno; i<10; i++) {
      delay(200);
    }
  }
}

void setup() {
  // for Leonardos, if you want to debug SD issues, uncomment this line
  // to see serial output
  //while (!Serial);
  
  // 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("\r\nUltimate GPSlogger Shield");
  pinMode(ledPin, OUTPUT);

  // make sure that the default chip select pin is set to
  // output, even if you don't use it:
  pinMode(10, OUTPUT);
  
  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect, 11, 12, 13)) {
  //if (!SD.begin(chipSelect)) {      // if you're using an UNO, you can use this line instead
    Serial.println("Card init. failed!");
    error(2);
  }
  char filename[15];
  strcpy(filename, "GPSLOG00.TXT");
  for (uint8_t i = 0; i < 100; i++) {
    filename[6] = '0' + i/10;
    filename[7] = '0' + i%10;
    // create if does not exist, do not open existing, write, sync after write
    if (! SD.exists(filename)) {
      break;
    }
  }

  logfile = SD.open(filename, FILE_WRITE);
  if( ! logfile ) {
    Serial.print("Couldnt create "); Serial.println(filename);
    error(3);
  }
  Serial.print("Writing to "); Serial.println(filename);
  
  // connect to the GPS at the desired rate
  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 logging data, we don't suggest using anything but either RMC only or RMC+GGA
  // to keep the log files at a reasonable size
  // Set the update rate
  GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ);   // 1 or 5 Hz update rate

  // Turn off updates on antenna status, if the firmware permits it
  GPS.sendCommand(PGCMD_NOANTENNA);
  
  Serial.println("Ready!");
}

void loop() {
  char c = GPS.read();
  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 trying 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
    
    // Sentence parsed! 
    Serial.println("OK");
    if (LOG_FIXONLY && !GPS.fix) {
        Serial.print("No Fix");
        return;
    }

    // Rad. lets log it!
    Serial.println("Log");
    
    char *stringptr = GPS.lastNMEA();
    uint8_t stringsize = strlen(stringptr);
    if (stringsize != logfile.write((uint8_t *)stringptr, stringsize))    //write the string to the SD file
      error(4);
    if (strstr(stringptr, "RMC"))   logfile.flush();
    Serial.println();
  }
}

Gracias