STM32_TestCall.ino

// Pin Definitions
#define POWER_KEY_PIN PA8  // Power key for the GSM module

// Create HardwareSerial for STM32 (UART2 is already set up in STM32CubeMX)
HardwareSerial sim800Serial(2);  // Using UART2

// Phone number to dial
String phoneNumber = "+1234567890";

void setup() {
  // Start Serial communication for debugging (for USB port)
  Serial.begin(9600);         // Communication with STM32 USB serial monitor
  sim800Serial.begin(9600);   // Communication with SIM800C module via UART2
  
  // Power on GSM module
  pinMode(POWER_KEY_PIN, OUTPUT);
  digitalWrite(POWER_KEY_PIN, HIGH);  // Set HIGH to power on the GSM module
  delay(3000);                      // Hold HIGH for 3 seconds
  digitalWrite(POWER_KEY_PIN, LOW);   // Set LOW to power it on
  
  // Allow time for SIM800C to initialize
  delay(5000); // Wait for GSM module to power up and initialize
  
  // Send a simple AT command to check if the GSM module is responsive
  sendATCommand("AT", 1000); // Send AT command to check for response
  
  // Make a call to the specified phone number
  makeCall(phoneNumber);
}

void loop() {
  // Nothing needs to be done in the loop for this example
}

// Function to send AT command and check for response
void sendATCommand(String command, unsigned long timeout) {
  Serial.print("Sending: ");
  Serial.println(command);
  
  sim800Serial.println(command);
  unsigned long startMillis = millis();
  
  while (millis() - startMillis < timeout) {
    if (sim800Serial.available()) {
      char c = sim800Serial.read();
      Serial.write(c);  // Print response from GSM module to serial monitor
    }
  }
}

// Function to make a call using the GSM module
void makeCall(String number) {
  String command = "ATD" + number + ";";  // ATD is the AT command for dialing a number
  sendATCommand(command, 5000);            // Dial the phone number
  
  Serial.println("Call initiated to: " + number);
  
  // Wait a bit before returning to ensure the call has been attempted
  delay(10000);  // Wait for the call to be connected or the timeout period
}