Tutorial: How to use SIM800L GSM Module using Arduino | Make or Answer Voice Calls

Here we will further our exploration with the SIM800L GSM Module by testing the voice call capability.

To make a voice call:
   1. Send ATD+ZZxxxxxxxxxx;<CR><LF>
      – this is tell the GSM module to dial the following mobile number
        ZZ – the country code of the mobile number you want to call
        xx – is the 10-digit mobile number
        ; – don’t forget semi-colon, it will error without the semi-colon
        CR – Cariage Return, ASCII character 13 or r
        LF – Line Feed, ASCII character 10 or n
 
To answer the incoming voice call:
   1. Send ATA<CR><LF>
      – this tells the GSM module to answer the incoming voice call
        CR – Cariage Return, ASCII character 13 or r
        LF – Line Feed, ASCII character 10 or n

To reject the incoming call or terminate ongoing call:
   1. Send ATH<CR><LF>
      – this tells the GSM module to hang up the call.
        CR – Cariage Return, ASCII character 13 or r
        LF – Line Feed, ASCII character 10 or n

Video Demonstration:

#include "SoftwareSerial.h"

SoftwareSerial mySerial(2, 3);

void setup(){

  Serial.begin(9600);
  mySerial.begin(9600);

}

void loop(){

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

}

Thank you and have a good day.