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SIM900A (Dual Band 900Mhz, 1800Mhz Celcom, Maxis only) Mini Size Module - Compatible with Arduino

1. IO Ports - RXD, TXD, Free USB to TTL for PC, supports 12000bps-115200bps, Supports AT commands GSM 07.07, 07.05, SIMCOM AT Extended commands
2. Anttena - SMA connector, comes with GSM 900M/1800M small antenna
3. Power Ports - DC 5V 2A 2.1 mm, BAT/GND connector for external mobile phone battery
4. SIM Slot - Support 1.8V/3V SIM card
5. Working Frequency - EGSM 900 Mhz/DCS 1800Mhz - Auto Dual Band
6. Size of PCB 59mm*43mm
7. With ESD Protection
8. With On/Off button and Power LED inidcator
9. Signal LED Indicator

#include 

#define KEY1 2

void setup()
{
    pinMode(KEY1, INPUT); 

    Serial.begin(9600);    //set baud rate to 9600
}

void loop()
{
    Scan_KEY();            
}

void SendMessage()
{
    Serial.print("AT+CSCS=");    
    Serial.print('"');    
    Serial.print("GSM");
    Serial.print('"');
    Serial.print(" ");

    delay(1000);
    Serial.print("AT+CMGF=1 ");
    delay(1000);
            
    Serial.print("AT+CMGS=");    
    Serial.print('"');    
    Serial.print("18067933376");            // set destination phone number
    Serial.print('"');
    Serial.print(" ");
    delay(1000);
    Serial.print("Hello World!");            // SMS
    delay(1000);
    Serial.write(0x1A);            // send
    delay(1000);
}



void Scan_KEY()                        // scan
{
    if( digitalRead(KEY1) == 0 )        // check if key is pressed
    {
        delay(20);                        
        if( digitalRead(KEY1) == 0 ) // check if key is pressed
        {            
            while(digitalRead(KEY1) == 0);        // key released
            SendMessage();
        }
    }
}