🔵 ESP32 Bluetooth Tutorial – Classic SPP vs BLE (Bluetooth Low Energy)

In this tutorial, you’ll learn how to use both Classic Bluetooth (SPP) and BLE (Bluetooth Low Energy) with your ESP32 to wirelessly communicate with a smartphone or computer.

You’ll understand the difference between SPP and BLE, when to use each, and how to build simple programs to send and receive data wirelessly using both methods.

🧠 Principle: What is Bluetooth?

Bluetooth is a wireless technology standard that allows devices to exchange data over short distances. ESP32 supports two Bluetooth protocols:

Bluetooth Type Description Use Case
🔵 Classic Bluetooth (SPP) Works like a virtual serial port Debugging, terminal communication
🟦 Bluetooth Low Energy (BLE) Efficient, low-power, event-driven Sensors, mobile apps, fitness devices

🧠 SPP vs BLE (Quick Comparison)

Feature Classic Bluetooth (SPP) BLE (Bluetooth Low Energy)
Power Consumption 🔋 Higher ⚡ Very low
Communication Style Stream-based (Serial-like) Event-based (GATT Services/Characteristics)
Supported on iPhone ❌ No ✅ Yes
Easy to use for Serial ✅ Yes ❌ Requires GATT structure
Best For Terminals, debug, data logs Mobile apps, sensors, low-power devices

📌 Use SPP for simplicity and fast testing (on Android only), and use BLE for battery-friendly, cross-platform communication.

🧪 Part 1: Classic Bluetooth (SPP) Example – Serial Communication

📲 Use Case: Send and receive text with phone (Android only)

🔧 Circuit: None needed (optional: connect LED to GPIO 2)

#include "BluetoothSerial.h"

BluetoothSerial SerialBT;

void setup() {
  Serial.begin(115200);
  SerialBT.begin("ESP32_SPP_Device");  // Bluetooth name
  pinMode(2, OUTPUT);
  Serial.println("Classic Bluetooth SPP started!");
}

void loop() {
  if (SerialBT.available()) {
    String received = SerialBT.readStringUntil('\n');
    Serial.print("Received: ");
    Serial.println(received);
    
    SerialBT.print("Echo: ");
    SerialBT.println(received);

    if (received == "ON") digitalWrite(2, HIGH);
    if (received == "OFF") digitalWrite(2, LOW);
  }
}

✅ Test With:

🧪 Part 2: Bluetooth Low Energy (BLE) Example – GATT Server

📲 Use Case: Send data to iPhone or Android BLE app

🔧 Circuit: Optional LED on GPIO 2

#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

BLECharacteristic* pCharacteristic;
bool deviceConnected = false;

class MyServerCallbacks : public BLEServerCallbacks {
  void onConnect(BLEServer* pServer) {
    deviceConnected = true;
    Serial.println("BLE Client Connected");
  }

  void onDisconnect(BLEServer* pServer) {
    deviceConnected = false;
    Serial.println("BLE Client Disconnected");
  }
};

void setup() {
  Serial.begin(115200);
  pinMode(2, OUTPUT);

  BLEDevice::init("ESP32_BLE_Device");
  BLEServer *pServer = BLEDevice::createServer();
  pServer->setCallbacks(new MyServerCallbacks());

  BLEService *pService = pServer->createService("180F");  // Battery Service UUID
  pCharacteristic = pService->createCharacteristic(
                      "2A19",  // Battery Level characteristic
                      BLECharacteristic::PROPERTY_READ |
                      BLECharacteristic::PROPERTY_NOTIFY |
                      BLECharacteristic::PROPERTY_WRITE
                    );

  pCharacteristic->addDescriptor(new BLE2902());
  pCharacteristic->setValue("Hello from ESP32!");
  pService->start();

  pServer->getAdvertising()->start();
  Serial.println("BLE advertising started!");
}

void loop() {
  if (deviceConnected) {
    pCharacteristic->setValue("Updated at " + String(millis()));
    pCharacteristic->notify();
    delay(2000);
  }
}

✅ Test With:

🔍 How It Works

Function Classic SPP BLE
SerialBT.begin(name) Starts Bluetooth Serial —
BLEDevice::init() — Initializes BLE stack
SerialBT.readString() Reads from Bluetooth —
pCharacteristic->setValue() — Sets value for BLE characteristic
pCharacteristic->notify() — Pushes updated value to client

🛠 When to Use Which?

Goal Use This
Quickly test Bluetooth with Android ✅ Classic SPP
Send sensor data to iPhone ✅ BLE
Create a mobile app with BLE scanner ✅ BLE
Serial-style debug monitor ✅ SPP
Build a low-power fitness band or beacon ✅ BLE

📚 Useful Resources