Adafruit_MQTT_Library/examples/mqtt_fona/fonahelper.cpp

#include "Adafruit_FONA.h"
#include <Adafruit_SleepyDog.h>
#include <SoftwareSerial.h>

#define halt(s)                                                                \
  {                                                                            \
    Serial.println(F(s));                                                      \
    while (1)                                                                  \
      ;                                                                        \
  }

extern Adafruit_FONA fona;
extern SoftwareSerial fonaSS;

boolean FONAconnect(const __FlashStringHelper *apn,
                    const __FlashStringHelper *username,
                    const __FlashStringHelper *password) {
  Watchdog.reset();

  Serial.println(F("Initializing FONA....(May take 3 seconds)"));

  fonaSS.begin(4800); // if you're using software serial

  if (!fona.begin(fonaSS)) { // can also try fona.begin(Serial1)
    Serial.println(F("Couldn't find FONA"));
    return false;
  }
  fonaSS.println("AT+CMEE=2");
  Serial.println(F("FONA is OK"));
  Watchdog.reset();
  Serial.println(F("Checking for network..."));
  while (fona.getNetworkStatus() != 1) {
    delay(500);
  }

  Watchdog.reset();
  delay(5000); // wait a few seconds to stabilize connection
  Watchdog.reset();

  fona.setGPRSNetworkSettings(apn, username, password);

  Serial.println(F("Disabling GPRS"));
  fona.enableGPRS(false);

  Watchdog.reset();
  delay(5000); // wait a few seconds to stabilize connection
  Watchdog.reset();

  Serial.println(F("Enabling GPRS"));
  if (!fona.enableGPRS(true)) {
    Serial.println(F("Failed to turn GPRS on"));
    return false;
  }
  Watchdog.reset();

  return true;
}