Module GSM GPRS SIM800L V2.0 5V

/* 
* Réaliser par Micro-Electroniques Générales au Maroc 
* Visite notre site megma.ma 
*/

#include <SoftwareSerial.h>
SoftwareSerial sim(10, 11);
int _timeout;
String _buffer;
String number = "+6281222329xxx"; //-> change with your number
void setup() {
//delay(7000); //delay for 7 seconds to make sure the modules get the signal
Serial.begin(9600);
_buffer.reserve(50);
Serial.println("Sistem Started...");
sim.begin(9600);
delay(1000);
Serial.println("Type s to send an SMS, r to receive an SMS, and c to make a call");
}
void loop() {
if (Serial.available() > 0)
switch (Serial.read())
{
case 's':
SendMessage();
break;
case 'r':
RecieveMessage();
break;
case 'c':
callNumber();
break;
}
if (sim.available() > 0)
Serial.write(sim.read());
}
void SendMessage()
{
//Serial.println ("Sending Message");
sim.println("AT+CMGF=1"); //Sets the GSM Module in Text Mode
delay(200);
//Serial.println ("Set SMS Number");
sim.println("AT+CMGS=\"" + number + "\"\r"); //Mobile phone number to send message
delay(200);
String SMS = "Hello, how are you? greetings from miliohm.com admin";
sim.println(SMS);
delay(100);
sim.println((char)26);// ASCII code of CTRL+Z
delay(200);
_buffer = _readSerial();
}
void RecieveMessage()
{
Serial.println ("SIM800L Read an SMS");
sim.println("AT+CMGF=1");
delay (200);
sim.println("AT+CNMI=1,2,0,0,0"); // AT Command to receive a live SMS
delay(200);
Serial.write ("Unread Message done");
}
String _readSerial() {
_timeout = 0;
while (!sim.available() && _timeout < 12000 )
{
delay(13);
_timeout++;
}
if (sim.available()) {
return sim.readString();
}
}
void callNumber() {
sim.print (F("ATD"));
sim.print (number);
sim.print (F(";\r\n"));
_buffer = _readSerial();
Serial.println(_buffer);
}