Simple example for getting started sending SMS (using a button to send the required CTRL+Z char)

7600_example.h

// First, wait for the green LED to go solid green
// Then, set the pin code using
// AT+CPIN=2643

// When the green LED blinks, you can check the name of the operator
// AT+CSPN?

// The turn on sending plain text messages (ASCII chars only)
// AT+CMGF=1

// Then start sending the message. The module will output a single ">" char. Then press the button to send!
// AT+CMGS="+4790691786"

#include <SoftwareSerial.h>
SoftwareSerial mySerial(8, 9);

const int buttonPin = 2;
int buttonState = 0;

void setup()
{
  delay(500);
  Serial.begin(115200);     // use these two lines on a new module using 115200 baud by default
  mySerial.begin(115200);
  
  //Serial.begin(19200);    // after changing the baud rate to 19200 using AT+IPR=19200, we use the speeds instead
  //mySerial.begin(19200);
  
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(buttonPin, INPUT);
  delay(1000);
}

int counter = 0;

void loop()
{
  /* send everything received from the hardware uart to usb serial & vv */
  if (Serial.available() > 0) {
    Serial.print(">");
    delay(100);
    while ( Serial.available() ) {
      char ch = Serial.read();
      Serial.print(ch);
      mySerial.print(ch);
    }
  }

  if (mySerial.available() > 0) {
    Serial.print(":");
    delay(10);
    while ( mySerial.available() ) {
      digitalWrite(LED_BUILTIN, HIGH);
      char ch = mySerial.read();
      if ( ch ) {
        Serial.print(ch);
      }
    }
  } else {
    digitalWrite(LED_BUILTIN, LOW);
  }

  buttonState = digitalRead(buttonPin);
  // check if the pushbutton is pressed. If it is, the buttonState is HIGH:
  if (buttonState == HIGH) {
    digitalWrite(LED_BUILTIN, HIGH); // Turn on the LED for debugging
    delay(200);
    mySerial.print("Testing SMS\r\n"); // type your message here
    mySerial.print(char(26));
    Serial.println("CRTL+Z was sent to the module!"); // just print in the Serial monitor that we sent the special char
  } else {
    delay(200);
    digitalWrite(LED_BUILTIN, LOW);
  }
}