Bluetooth LE Gatt Example, step-by-step

Last post demonstrate the Android Bluetooth Le Gatt example code with Arduino/Genuino 101. This post start to (TRY to) implement my own Bluetooth LE Gatt Example, step-by-step. The aim of the examples (in coming series) are scan BLE device, find and link with specified device Genuino 101 (programmed with "LEDCB", refer previous post), and read and write characteristic of the device to turn ON/OFF the Genuino 101 on-board LED.

The main reference material are:
- Android Developers Guide > Bluetooth Low Energy
- The Android example code - BluetoothLeGatt. (The example in last post)

In this first step, create a new project in Android Studio, named AndroidBleGatt.

In my example (in coming post) I will scan LE device using BluetoothLeScanner (Added in API level 21) instead of calling deprecated startLeScan() and stopLeScan() methods as in the BluetoothLeGatt example, so specify the Min Sdk Version of API 21.

Edit AndroidManifest.xml to add uses-feature of "android.hardware.bluetooth_le", uses-permission of "android.permission.BLUETOOTH", "android.permission.BLUETOOTH_ADMIN" and "android.permission.ACCESS_COARSE_LOCATION".

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.blogspot.android_er.androidblegatt">

    <uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>
    <uses-permission android:name="android.permission.BLUETOOTH"/>
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Edit MainActivity.java

package com.blogspot.android_er.androidblegatt;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothManager;
import android.bluetooth.le.BluetoothLeScanner;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private BluetoothAdapter mBluetoothAdapter;
    private BluetoothLeScanner mBluetoothLeScanner;

    private boolean mScanning;

    private static final int RQS_ENABLE_BLUETOOTH = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Check if BLE is supported on the device.
        if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
            Toast.makeText(this,
                    "BLUETOOTH_LE not supported in this device!",
                    Toast.LENGTH_SHORT).show();
            finish();
        }

        getBluetoothAdapterAndLeScanner();

        // Checks if Bluetooth is supported on the device.
        if (mBluetoothAdapter == null) {
            Toast.makeText(this,
                    "bluetoothManager.getAdapter()==null",
                    Toast.LENGTH_SHORT).show();
            finish();
            return;
        }

    }

    @Override
    protected void onResume() {
        super.onResume();

        if (!mBluetoothAdapter.isEnabled()) {
            if (!mBluetoothAdapter.isEnabled()) {
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, RQS_ENABLE_BLUETOOTH);
            }
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        if (requestCode == RQS_ENABLE_BLUETOOTH && resultCode == Activity.RESULT_CANCELED) {
            finish();
            return;
        }

        getBluetoothAdapterAndLeScanner();

        // Checks if Bluetooth is supported on the device.
        if (mBluetoothAdapter == null) {
            Toast.makeText(this,
                    "bluetoothManager.getAdapter()==null",
                    Toast.LENGTH_SHORT).show();
            finish();
            return;
        }

        super.onActivityResult(requestCode, resultCode, data);
    }

    private void getBluetoothAdapterAndLeScanner(){
        // Get BluetoothAdapter and BluetoothLeScanner.
        final BluetoothManager bluetoothManager =
                (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        mBluetoothAdapter = bluetoothManager.getAdapter();
        mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();

        mScanning = false;
    }
}

Up to here, the app simple check Bluetooth LE available and enable it. In next post, I will show how to scan available Bluetooth LE devices in range.

Next:
- Bluetooth LE Gatt Example, scan BLE devices
- Scan specified BLE devices with ScanFilter
- Connect to Bluetooth LE device and display GATT Services

Bluetooth Le Gatt example to link with Arduino/Genuino 101

This post show how to run the Android Bluetooth Le Gatt example Code to link with Arduino/Genuino 101.

The Arduino/Genuino 101 board contains the Intel® Curie™ Module. The 101 adds Bluetooth Low Energy capabilities and has an on-board 6-axis accelerometer/gyroscope, providing exciting opportunities for building creative projects in the connected world. More information about the technical specifications and documentation can be found on the Arduino/Genuino 101 main page.

In Arduino/Genuino 101 board, program with example:
> File > Examples > CurieBLE > CallbackLED


This example setup Arduino/Genuino 101 as Bluetooth LE device (named "LEDCB") with service with UUID "19B10000-E8F2-537E-4F6C-D104768A1214" and create switch characteristic allowing remote device to read and write, with UUID "19B10001-E8F2-537E-4F6C-D104768A1214". We need the UUIDs in future examples.

So I copy here for future reference:

/*
  Copyright (c) 2015 Intel Corporation. All rights reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-
  1301 USA
*/


#include <CurieBLE.h>

const int ledPin = 13; // set ledPin to use on-board LED
BLEPeripheral blePeripheral; // create peripheral instance

BLEService ledService("19B10000-E8F2-537E-4F6C-D104768A1214"); // create service

// create switch characteristic and allow remote device to read and write
BLECharCharacteristic switchChar("19B10001-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite);

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT); // use the LED on pin 13 as an output

  // set the local name peripheral advertises
  blePeripheral.setLocalName("LEDCB");
  // set the UUID for the service this peripheral advertises
  blePeripheral.setAdvertisedServiceUuid(ledService.uuid());

  // add service and characteristic
  blePeripheral.addAttribute(ledService);
  blePeripheral.addAttribute(switchChar);

  // assign event handlers for connected, disconnected to peripheral
  blePeripheral.setEventHandler(BLEConnected, blePeripheralConnectHandler);
  blePeripheral.setEventHandler(BLEDisconnected, blePeripheralDisconnectHandler);

  // assign event handlers for characteristic
  switchChar.setEventHandler(BLEWritten, switchCharacteristicWritten);
// set an initial value for the characteristic
  switchChar.setValue(0);

  // advertise the service
  blePeripheral.begin();
  Serial.println(("Bluetooth device active, waiting for connections..."));
}

void loop() {
  // poll peripheral
  blePeripheral.poll();
}

void blePeripheralConnectHandler(BLECentral& central) {
  // central connected event handler
  Serial.print("Connected event, central: ");
  Serial.println(central.address());
}

void blePeripheralDisconnectHandler(BLECentral& central) {
  // central disconnected event handler
  Serial.print("Disconnected event, central: ");
  Serial.println(central.address());
}

void switchCharacteristicWritten(BLECentral& central, BLECharacteristic& characteristic) {
  // central wrote new value to characteristic, update LED
  Serial.print("Characteristic event, written: ");

  if (switchChar.value()) {
    Serial.println("LED on");
    digitalWrite(ledPin, HIGH);
  } else {
    Serial.println("LED off");
    digitalWrite(ledPin, LOW);
  }
}

In Android side, load with example code of Bluetooth Le Gatt:


How it run:


This demo haven't show any real function indeed. In coming posts, I will TRY to implement my own example app (with re-using part of the Bluetooth Le Gatt example) to control and read state from Genuino 101. Currently, I don't know how much I can.

Check if your Android device support Bluetooth Low Energy

Android 4.3 (API Level 18) introduces built-in platform support for Bluetooth Low Energy in the central role and provides APIs that apps can use to discover devices, query for services, and read/write characteristics.

To check if your device support Bluetooth Low Energy programmically, check (getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)).

Nexus 7, 1st gen, not support BlueTooth LE!

MK 908III Android mini PC support both Bluetooth and Bluetooth LE

package com.example.androidcheckbtle;

import android.support.v7.app.ActionBarActivity;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  TextView textManufacturer = (TextView)findViewById(R.id.manufacturer);
  TextView textModel = (TextView)findViewById(R.id.model);
  TextView textSupportBT = (TextView)findViewById(R.id.supportbt);
  TextView textSupportBTLE = (TextView)findViewById(R.id.supportbtle);
  
  //Get brand, manufacturer and model of your device
  textManufacturer.setText(Build.BRAND + " : " + Build.MANUFACTURER);
  textModel.setText(Build.MODEL);
  
  //Check if your device support BlueTooth
  if (getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH)){
   textSupportBT.setText("Support BLUETOOTH");
  }else{
   textSupportBT.setText("NOT Support BLUETOOTH");
  }
  
  //Check if your device support Bluetooth Low Energy
  if (getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)){
   textSupportBTLE.setText("Support BLUETOOTH_LE");
  }else{
   textSupportBTLE.setText("NOT Support BLUETOOTH_LE");
  }
 }

}

/res/layout/activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="com.example.androidcheckbtle.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/manufacturer"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/model"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/supportbt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/supportbtle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    
</LinearLayout>