✅ ESP32 + DHT11 + Bluetooth Terminal (COPY–PASTE CODE)

#include <DHT.h>
#include "BluetoothSerial.h"

// -------------------- Bluetooth Check --------------------
#if !defined(CONFIG_BT_ENABLED) || !defined(CONFIG_BLUEDROID_ENABLED)
#error Bluetooth is not enabled! Please enable it in ESP32 settings
#endif

// -------------------- Bluetooth Object --------------------
BluetoothSerial SerialBT;

// -------------------- DHT Setup --------------------
#define DHTPIN 4 // GPIO4 (D4)
#define DHTTYPE DHT11 // Sensor type

DHT dht(DHTPIN, DHTTYPE);

void setup() {
// Start Serial Monitor
Serial.begin(115200);

// Start Bluetooth with device name
SerialBT.begin("ESP32_DHT11");

// Startup messages
Serial.println("ESP32 DHT11 Bluetooth Started");
SerialBT.println("ESP32 DHT11 Bluetooth Started");

// Start DHT sensor
dht.begin();
}

void loop() {
// DHT11 needs at least 2 seconds delay between readings
delay(2000);

// Read humidity and temperature
float humidity = dht.readHumidity();
float temperature = dht.readTemperature(); // Celsius

// Check if sensor reading failed
if (isnan(humidity) || isnan(temperature)) {
Serial.println("Failed to read from DHT sensor");
SerialBT.println("Failed to read from DHT sensor");
return;
}

// -------------------- Serial Monitor Output --------------------
Serial.print("Temperature: ");
Serial.print(temperature);
Serial.print(" °C | Humidity: ");
Serial.print(humidity);
Serial.println(" %");

// -------------------- Bluetooth Terminal Output --------------------
SerialBT.print("Temperature: ");
SerialBT.print(temperature);
SerialBT.print(" °C | Humidity: ");
SerialBT.print(humidity);
SerialBT.println(" %");
}

🔌 Wiring (DHT11 → ESP32)

📱 How to Use Bluetooth Terminal App

Step 1

Upload code to ESP32.

Step 2

Open phone Bluetooth → pair with:
✅ ESP32_DHT11

Step 3

Open Bluetooth Terminal App and connect.

Now you will see:

🧠 Detailed Code Explanation (Teaching Style)

✅ 1) Library Include

🔹 DHT.h

Used to read:

• Temperature

• Humidity

🔹 BluetoothSerial.h

Used to send/receive data through:

• Bluetooth Classic Serial (like HC-05)

✅ 2) Bluetooth Enabled Check

This checks if Bluetooth is enabled in ESP32 settings.

If Bluetooth is disabled, it stops compilation and shows an error.

✅ 3) Create Bluetooth Object

This creates a Bluetooth Serial object called SerialBT.

Now you can use:

• SerialBT.begin()

• SerialBT.print()

• SerialBT.println()

✅ 4) DHT Pin and Type

🔹 DHTPIN 4

DHT11 DATA pin is connected to ESP32 GPIO4.

🔹 DHTTYPE DHT11

Tells library you are using DHT11.

✅ 5) Create DHT Object

This creates a DHT object named dht.

Now ESP32 can communicate with DHT11.

✅ 6) setup() Function

Runs only once when ESP32 starts.

🔹 Serial Monitor Start

Starts serial communication with computer.

🔹 Bluetooth Start

This starts Bluetooth and sets device name:

📌 Phone will see:
✅ ESP32_DHT11

🔹 Print Startup Messages

This prints the same message:

• On Serial Monitor

• On Bluetooth Terminal

So user knows it started successfully.

🔹 Start DHT Sensor

This initializes DHT11 sensor.

✅ 7) loop() Function

This runs again and again forever.

🔹 Delay

DHT11 needs minimum 2 seconds delay.

If you remove this:

• readings become wrong

• or NAN

✅ 8) Read Sensor Data

humidity

Reads humidity in percentage.

temperature

Reads temperature in Celsius.

✅ 9) Error Checking

If wiring is wrong or sensor fails, values become:

❌ NAN (Not a Number)

So we print error.

✅ 10) Print Data (Serial + Bluetooth)

Serial Monitor

Bluetooth Terminal

Both will show the same output.

✅ Final Output Example

Serial Monitor

Bluetooth Terminal App