The document provides an overview of using Arduino and Android for controlling Christmas tree lights via Bluetooth Low Energy (BLE). It explains key concepts related to BLE, Arduino programming, and the structure of an Arduino sketch. Additionally, it includes code snippets for managing device connections and controlling LED effects through an Android application.

2. Agenda
1. Overview and BLE Basics
2. Arduino
3. Android
4. Demo + Q&A

3. The big picture
Effect
Color
O Off
O Steady
O Blink
Remote controlling of the Christmas tree lights

4. How to do?
Android
Smartphone App
Bluetooth Low Energy
Connectivity
Arduino-based
prototype

5. What is Arduino?
Arduino is a global leader
in open-source hardware and software
It provides a platform for building electronic prototypes,
designed to be accessible to all
It promotes sharing and transparency,
creating a collaborative ecosystem
Large and active community (> 30M developers)

6. The magic within the tree
The board
Arduino Nano 33 BLE
The strip light
NeoPixel WS2812B
Addressable color LEDs
The power supply
12VDC
● Development board part of Nano series
● BLE feature
● Integrated sensors: acc, gyro, …
● I/O pins: digital and analog

7. Bluetooth Low Energy 101
BLE is a communication technology based on Bluetooth and
designed for energy efficiency
Client-Server architecture (Central-Peripheral)
Supported by a wide range of devices
Widely used in fitness trackers, smart home devices, industrial
sensors, and other IoT applications
Central
(Client)
Peripheral
(Server)

8. BLE: Services & Characteristics
A Peripheral organizes and exchanges data through:
● Services: a collection of related functionalities
● Characteristics: a specific piece of information within a Service
Effect
Characteristic
Color
Characteristic
Led
Service
A Characteristic:
● Has Read/Write/Notify properties
● Is identified by an UUID
● Has a fixed length (up to 20 bytes)
Represents the light effect
(0=Off, 1=Steady, etc.)
Represents the light color
(3 bytes: R,G,B)

9. BLE: Scan & Advertising
Scan: The action performed by a central to
find nearby peripherals
Advertising: A peripheral actively
announces its presence and share
information about its identity and features
Central
Peripheral
“Hi all! My name is
GDG-Arduino and
I offer Led Service feature.”
“Hey! Is anyone there?”

10. Arduino: Let’s code!

11. The sketch
A program written for an Arduino board
Two main parts:
● setup(): Initializes variables, features,
runs once at the beginning
● loop(): main code that runs repeatedly
Key tasks:
● Advertising to make device discoverable by the
Android app
● Provide LED strip control functionalities

12. Let’s begin!
#include <ArduinoBLE.h> // Arduino BLE Library
void setup() {
// BLE initialization
BLE.begin();
// Set advertised local name
BLE.setLocalName("GDG-Arduino");

13. Exposing features
BLEService ledService("1e03ce00-b8bc-4152-85e2-f096236d2833");
BLEByteCharacteristic ledEffectCharacteristic("...", BLERead | BLEWrite);
BLECharacteristic ledColorCharacteristic("...", BLERead | BLEWrite, 3);
ledService.addCharacteristic(ledEffectCharacteristic);
ledService.addCharacteristic(ledColorCharacteristic);
BLE.addService(ledService);
BLE.setAdvertisedService(ledService);
BLE.advertise();
Add Characteristics inside
the Led service
Services and Characteristics
declaration
Add Service
inside the peripheral BLE stack
Start advertising
UUID: randomically generated
Properties

14. Managing App requests (1/2)
void loop() {
BLEDevice central = BLE.central(); // listen for BLE central to connect
if (central) { // if a central is connected to peripheral
while (central.connected()) {
// Check ledEffect characteristic write
if (ledEffectCharacteristic.written()) {
ledEffect = ledEffectCharacteristic.value();
}
applyEffect(ledEffect);
}
}

15. ledStrip is an instance of the library
<Adafruit_NeoPixel.h> used to simplify the
control of NeoPixel RGB LED strips
Managing App requests (2/2)
void applyEffect(byte effect) {
…
switch(effect) {
case OFF_EFFECT:
ledStrip.clear();
ledStrip.show();
break;
case STEADY_EFFECT:
// Set all pixels to the specified color
for (int i = 0; i < LED_NUM; i++) {
ledStrip.setPixelColor(i, ledColor[0], ledColor[1], ledColor[2]);
}
ledStrip.show();
break;
…

16. Use BLE on Android

17. Permissions on Android <= 11
ACCESS_FINE_LOCATION
BLUETOOTH BLUETOOTH_ADMIN

18. Permissions on Android >= 12
BLUETOOTH_SCAN
BLUETOOTH_ADVERTISE
BLUETOOTH_CONNECT ACCESS_FINE_LOCATION

19. BLE Adapter
val bleManager = context.getSystemService(BLUETOOTH_SERVICE) as BluetoothManager

20. BLE Key Steps
SCAN CONNECT

21. BLE Scan Configuration
SCAN SETTINGS
SCAN FILTER ScanFilter.Builder().setServiceUuid(<UUID>)
ScanSettings.Builder()
.setScanMode(ScanSettings.SCAN_MODE_LOW_POWER)
You can also filter for:
MAC Address, device name, Manufacturer Data
There are 4 types of scan mode!

22. BLE Scan Callback
val scanCallback = object : ScanCallback() {
override fun onScanResult(callbackType: Int, result: ScanResult) {
with(result.device) {
Log.i(“ScanCallback”, "Found BLE device! Name: ${name ?: "Unnamed"},
address: $address")
}
}
}
SCAN RESULT
BLUETOOTH DEVICE
RSSI
SCAN RECORD

23. BLE Scan Execution
_bleManager.adapter.bluetoothLeScanner?.startScan(
mutableListOf(scanFilter), scanSettings, scanCallback
)
_bleManager.adapter.bluetoothLeScanner?.stopScan(scanCallback)

24. BLE GATT Callback
override fun onConnectionStateChange(gatt: BluetoothGatt?, status: Int, newState: Int)
override fun onServicesDiscovered(gatt: BluetoothGatt?, status: Int)
override fun onCharacteristicRead(
gatt: BluetoothGatt?,
characteristic: BluetoothGattCharacteristic?,
status: Int
)
override fun onCharacteristicWrite(
gatt: BluetoothGatt?,
characteristic: BluetoothGattCharacteristic?,
status: Int
)
override fun onCharacteristicChanged(
gatt: BluetoothGatt?,
characteristic: BluetoothGattCharacteristic?
)

25. BLE Device Connection
bleManager.adapter.getRemoteDevice(“macAddress”)?.let {
mBluetoothGatt = bluetoothDevice?.connectGatt(context, false, gattCallback)
}
BLE Device Disconnection
mBluetoothGatt?.disconnect()

26. BLE Discover Services
mBluetoothGatt?.discoverServices()

27. BLE Device Read Characteristic
fun readLEDColor(): Boolean? {
val service = mBluetoothGatt?.getService(LedUUID.LedService.uuid)
val characteristic =
service?.getCharacteristic(LedUUID.LedService.Color.uuid)
return mBluetoothGatt?.readCharacteristic(characteristic)
}

28. BLE Device Write Characteristic (1/2)
fun setLEDEffect(effectIndex: Int): Boolean? {
val service = mBluetoothGatt?.getService(LedUUID.LedService.uuid)
val characteristic =
service?.getCharacteristic(LedUUID.LedService.Effect.uuid)
val payload = byteArrayOf(effectIndex.toByte())
return sendCommand(characteristic, payload)
}

29. BLE Device Write Characteristic (2/2)
fun sendCommand(
characteristic: BluetoothGattCharacteristic?,
payload: ByteArray
): Boolean? {
characteristic?.let {
val result = mBluetoothGatt?.writeCharacteristic(
characteristic,
payload,
BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT
)
val res = when (result) {
BluetoothStatusCodes.SUCCESS -> true
else -> false
}
return res
}
}

30. BLE Common Problems
1. Android can manage up to 32 BLE connections
2. You cannot run more than 5 scan in 30 sec.
3. You cannot connect a device directly without scan unless you have bonded it
4. You have to manage your BLE instance yourself, if you saturate it an 133 Error can occur
5. Before Scan or Connect you have to check yourself if BLE is on/off
(you can do it by using bleManager.adapter.isEnabled).
“FUN FACT”: This information is not present in the documentation 😁

31. Q&A

32. DEMO TIME
Android Code: https://github.com/appersiano/GDG_LedStripTree_Android
Arduino Code: https://github.com/leonardocavagnis/GDG_LedStripTree_Arduino

33. THANK YOU!
Alessandro Persiano
Email: appersiano@gmail.com
LinkedIn: alessandro-persiano
GitHub: appersiano
Leonardo Cavagnis
Email: l.cavagnis@arduino.cc
LinkedIn: leonardocavagnis
GitHub: leonardocavagnis

34. CHALLENGE TIME!
https://kahoot.it