Timothy Woo
Published © CC BY-SA

ESP32 BLE + Android + Arduino IDE = AWESOME

Experience the power of the ESP32's Bluetooth Low Energy capabilities with Arduino IDE and build your own custom Android app to control it!

IntermediateProtip15 minutes23,326
ESP32 BLE + Android + Arduino IDE = AWESOME

Things used in this project

Hardware components

ESP32 Dev Board
Pretty much any ESP32 development board will work but the LED pin number might differ!
×1
Android device
Android device
Make sure your device is BLE-compatible! (Bluetooth 4.0 or later)
×1
USB-A to Micro-USB Cable
USB-A to Micro-USB Cable
For programming your ESP32 board.
×1

Software apps and online services

Arduino IDE
Arduino IDE
Thunkable
This is a wonderful visual app-building tool for Android and iOS!

Story

Read more

Code

ESP32 BLE Arduino Code

Arduino
/*
    Video: https://www.youtube.com/watch?v=oCMOYS71NIU
    Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleNotify.cpp
    Ported to Arduino ESP32 by Evandro Copercini

   Create a BLE server that, once we receive a connection, will send periodic notifications.
   The service advertises itself as: 6E400001-B5A3-F393-E0A9-E50E24DCCA9E
   Has a characteristic of: 6E400002-B5A3-F393-E0A9-E50E24DCCA9E - used for receiving data with "WRITE" 
   Has a characteristic of: 6E400003-B5A3-F393-E0A9-E50E24DCCA9E - used to send data with  "NOTIFY"

   The design of creating the BLE server is:
   1. Create a BLE Server
   2. Create a BLE Service
   3. Create a BLE Characteristic on the Service
   4. Create a BLE Descriptor on the characteristic
   5. Start the service.
   6. Start advertising.

   In this example rxValue is the data received (only accessible inside that function).
   And txValue is the data to be sent, in this example just a byte incremented every second. 
*/
#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

BLECharacteristic *pCharacteristic;
bool deviceConnected = false;
float txValue = 0;
const int readPin = 32; // Use GPIO number. See ESP32 board pinouts
const int LED = 2; // Could be different depending on the dev board. I used the DOIT ESP32 dev board.

//std::string rxValue; // Could also make this a global var to access it in loop()

// See the following for generating UUIDs:
// https://www.uuidgenerator.net/

#define SERVICE_UUID           "6E400001-B5A3-F393-E0A9-E50E24DCCA9E" // UART service UUID
#define CHARACTERISTIC_UUID_RX "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
#define CHARACTERISTIC_UUID_TX "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"

class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      deviceConnected = true;
    };

    void onDisconnect(BLEServer* pServer) {
      deviceConnected = false;
    }
};

class MyCallbacks: public BLECharacteristicCallbacks {
    void onWrite(BLECharacteristic *pCharacteristic) {
      std::string rxValue = pCharacteristic->getValue();

      if (rxValue.length() > 0) {
        Serial.println("*********");
        Serial.print("Received Value: ");

        for (int i = 0; i < rxValue.length(); i++) {
          Serial.print(rxValue[i]);
        }

        Serial.println();

        // Do stuff based on the command received from the app
        if (rxValue.find("A") != -1) { 
          Serial.println("Turning ON!");
          digitalWrite(LED, HIGH);
        }
        else if (rxValue.find("B") != -1) {
          Serial.println("Turning OFF!");
          digitalWrite(LED, LOW);
        }

        Serial.println();
        Serial.println("*********");
      }
    }
};

void setup() {
  Serial.begin(115200);

  pinMode(LED, OUTPUT);

  // Create the BLE Device
  BLEDevice::init("ESP32 UART Test"); // Give it a name

  // Create the BLE Server
  BLEServer *pServer = BLEDevice::createServer();
  pServer->setCallbacks(new MyServerCallbacks());

  // Create the BLE Service
  BLEService *pService = pServer->createService(SERVICE_UUID);

  // Create a BLE Characteristic
  pCharacteristic = pService->createCharacteristic(
                      CHARACTERISTIC_UUID_TX,
                      BLECharacteristic::PROPERTY_NOTIFY
                    );
                      
  pCharacteristic->addDescriptor(new BLE2902());

  BLECharacteristic *pCharacteristic = pService->createCharacteristic(
                                         CHARACTERISTIC_UUID_RX,
                                         BLECharacteristic::PROPERTY_WRITE
                                       );

  pCharacteristic->setCallbacks(new MyCallbacks());

  // Start the service
  pService->start();

  // Start advertising
  pServer->getAdvertising()->start();
  Serial.println("Waiting a client connection to notify...");
}

void loop() {
  if (deviceConnected) {
    // Fabricate some arbitrary junk for now...
    txValue = analogRead(readPin) / 3.456; // This could be an actual sensor reading!

    // Let's convert the value to a char array:
    char txString[8]; // make sure this is big enuffz
    dtostrf(txValue, 1, 2, txString); // float_val, min_width, digits_after_decimal, char_buffer
    
//    pCharacteristic->setValue(&txValue, 1); // To send the integer value
//    pCharacteristic->setValue("Hello!"); // Sending a test message
    pCharacteristic->setValue(txString);
    
    pCharacteristic->notify(); // Send the value to the app!
    Serial.print("*** Sent Value: ");
    Serial.print(txString);
    Serial.println(" ***");

    // You can add the rxValue checks down here instead
    // if you set "rxValue" as a global var at the top!
    // Note you will have to delete "std::string" declaration
    // of "rxValue" in the callback function.
//    if (rxValue.find("A") != -1) { 
//      Serial.println("Turning ON!");
//      digitalWrite(LED, HIGH);
//    }
//    else if (rxValue.find("B") != -1) {
//      Serial.println("Turning OFF!");
//      digitalWrite(LED, LOW);
//    }
  }
  delay(1000);
}

Android APK App File

Java
This is the final app file that you should end up with after compiling your Thunkable app. You can install this file directly onto your Android device or use Thunkable Live to generate a QR code instead.
No preview (download only).

Thunkable Android App Native File

Java
Load this file in Thunkable to view and edit the app!
No preview (download only).

ESP32 Package for Arduino

This is the official ESP32 package for Arduino IDE

Credits

Timothy Woo

Timothy Woo

7 projects • 75 followers
I'm a young engineer with a passion for DIY and electronics! My motto is "Learn to share, share to learn!"
Thanks to Neil Kolban.

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