/*
  HC-05 Bluetooth Module — Combined Sample Sketch
  Tishvi Docs · guide.tishvi.com

  Wiring (Arduino UNO R3):
    HC-05 VCC  -> Arduino 5V
    HC-05 GND  -> Arduino GND
    HC-05 TXD  -> Arduino D2                 (direct — 3.3V registers as HIGH)
    HC-05 RXD  -> Arduino D3, via a voltage divider:
                    D3 -> R1 (1kΩ) -> RXD -> R2 (2kΩ) -> GND
                  (never wire RXD straight to a 5V pin)
    LED        -> Arduino pin 13 (built-in LED works fine)

  What it does:
    - Bridges Serial Monitor <-> Bluetooth so you can confirm the module
      is wired correctly (type in either window, see it in the other).
    - Also listens for '1' / '0' over Bluetooth to turn the LED on/off.

  Pairing:
    Default PIN is usually 1234 or 0000. Use a Bluetooth serial terminal
    app (e.g. "Serial Bluetooth Terminal" on Android) to connect and send
    characters.

  Baud rate:
    9600 — this is the HC-05's default DATA mode baud rate. If you've
    changed it with an AT+UART command, update BTSerial.begin() below
    to match.

  Library:
    SoftwareSerial — built into the Arduino IDE, no installation needed.
*/

#include <SoftwareSerial.h>

SoftwareSerial BTSerial(2, 3); // RX, TX — D2<-HC-05 TXD, D3->HC-05 RXD
const int ledPin = 13;

void setup() {
  pinMode(ledPin, OUTPUT);

  Serial.begin(9600);
  BTSerial.begin(9600);

  Serial.println("HC-05 ready. Pair with 'HC-05' on your phone (PIN 1234 or 0000).");
  Serial.println("Send '1' or '0' over Bluetooth to control the LED.");
}

void loop() {
  // Anything received over Bluetooth...
  if (BTSerial.available()) {
    char c = BTSerial.read();

    // ...is echoed to the Serial Monitor for debugging
    Serial.write(c);

    // ...and checked for LED commands
    if (c == '1') {
      digitalWrite(ledPin, HIGH);
      BTSerial.println("LED ON");
    } else if (c == '0') {
      digitalWrite(ledPin, LOW);
      BTSerial.println("LED OFF");
    }
  }

  // Anything typed in Serial Monitor is sent out over Bluetooth
  if (Serial.available()) {
    BTSerial.write(Serial.read());
  }
}