Arduino Mega with SIM800L

sim800l.ino

#include <SoftwareSerial.h>
/* Tutorial link:  https://pijaeducation.com/arduino/gsm/send-receive-messages-using-sim800l-with-arduino/
   Create software serial pins: pin 2 as RX & 3 as TX
   Connect SIM800L module Rx to Pin 3 (Tx) of Arduino & Tx to Pin 2 (Rx) of Arduino
*/

/*
Not all pins on the Mega and Mega 2560 boards support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69). Not all pins on the Leonardo and Micro boards support change interrupts, so only the following can be used for RX: 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI).
*/
#define rx 10
#define tx 11
SoftwareSerial mySerial(rx, tx);

void setup() {
  pinMode(rx, INPUT);
  pinMode(tx, OUTPUT);
  Serial.begin(9600);
  mySerial.begin(9600);
  Serial.println("Initializing...");
  for (int i =0; i < 30; i++) {
    Serial.print(".");
    delay(1000);
  }
  Serial.println(".");

  Serial.println("Send attention command to check if all fine, it returns OK");
  mySerial.println("AT");
  updateSerial();

  Serial.println("Signal quality test, value range is 0 - 31 , 31 is the Excellent");
  mySerial.println("AT+CSQ");
  updateSerial();

  Serial.println("Used to read the ICCID from the SIM, if returns means SIM is plugged");
  mySerial.println("AT+CCID");
  updateSerial();

  Serial.println("Check whether it has registered on the network");
  mySerial.println("AT+CREG?");
  updateSerial();

  Serial.println("Configuring module in TEXT mode");
  mySerial.println("AT+CMGF=1");
  updateSerial();

  Serial.println("Decides how newly arrived SMS messages should be handled");
  mySerial.println("AT+CNMI=1,2,0,0,0");   
  updateSerial();
}

void loop() {
  updateSerial();
}

// For data transmission from Serial to Software Serial port & vice versa
void updateSerial() {
  delay(500);
    while (mySerial.available()) {

    Serial.write(mySerial.read());//Forward what Software Serial received to Serial Port
  }
  while (Serial.available()) {
    mySerial.write(Serial.read());//Forward what Serial received to Software Serial Port
  }


}