// ESP32 Sender - Sends "hello" every 5 seconds and receives "ciao"
#include <Arduino.h>

// Define UART pins
#define RX_PIN 16  // GPIO16 for UART2 RX
#define TX_PIN 17  // GPIO17 for UART2 TX

// Timer variables
unsigned long previousMillis = 0;
const long interval = 5000;  // 5 seconds interval

void setup() {
  // Initialize Serial Monitor for debugging
  Serial.begin(115200);
  Serial.println("ESP32 Sender Initialized");
  
  // Initialize UART2 for communication with the second ESP32
  Serial2.begin(9600, SERIAL_8N1, RX_PIN, TX_PIN);
}

void loop() {
  // Check if 5 seconds have passed
  unsigned long currentMillis = millis();
  
  if (currentMillis - previousMillis >= interval) {
    // Save the last time a message was sent
    previousMillis = currentMillis;
    
    // Send "hello" to the other ESP32
    Serial2.println("hello");
    Serial.println("Sent: hello");
  }
  
  // Check if data is available from the other ESP32
  if (Serial2.available()) {
    // Read the incoming message
    String message = Serial2.readStringUntil('\n');
    message.trim();  // Remove any whitespace or newline characters
    
    // Print received message
    Serial.print("Received: ");
    Serial.println(message);
  }
}