android蓝牙4.0(BLE)开发之ibeacon初步

少年恃险若平地,独倚长剑凌清秋。这篇文章主要讲述android蓝牙4.0(BLE)开发之ibeacon初步相关的知识,希望能为你提供帮助。

此文使用的ibeacon模块是april beacon,至于什么是ibeacon。本文不做解释,具体请自查。
一个april beacon里携带的信息如下
0201061AFF4C0002159069BDB88C11416BAC3F33468C2788A3044B0378C60C09417072696C426561636F6E051250002003020A0000000000000000000000

具体是什么意思呢
02Number of bytes that follow in first AD structure 01Flags AD type 06 Flags value 0x1A = 000011010 bit 0 (OFF) LE Limited Discoverable Mode bit 1 (ON) LE General Discoverable Mode bit 2 (OFF) BR/EDR Not Supported bit 3 (ON) Simultaneous LE and BR/EDR to Same Device Capable (controller) bit 4 (ON) Simultaneous LE and BR/EDR to Same Device Capable (Host) 1a Number of bytes that follow in second (and last) AD structure 前面是常规智能硬件广播包部分ff (FF代表后面是Manufacture Data)4c 00(组织标识,0x4c00苹果公司标识,https://www.bluetooth.org/en-us/specification/assigned-numbers/company-identifiers) 02 (0x02 ibeacon标识位) 15 (0x15,22个字节标识长度,uuid,major,minor总和的长度) 90 69 bd b8-8c 11-41 6b-ac 3f-33 46 8c 27 88 a3 (Proximity UUID) 04 4b(1099,major) 03 78(888,minor) c6(切记这里是补码,转化为原码就是-58,iBeacon的信号发出强度值,用来作为和RSSI一起测距的基准 ,txPower) 计算 C6 1100 0110 补码 1100 0101 反码 1011 1010 原码 -(32+16+8+2) -58 0c09(未知) 417072696c426561636f6e(AprilBeacon字符串对应的十六进制) 051250002003020a0000000000000000000000(未知)

Proximity UUID :这是将你所有的beacon与其他人的beacon设备区别开的id!例如,目前在商店里某个区域分布着多个beacon形成一条“链带”,用于为顾客提供特定的服务,那么归属于同一条“链带”的beacon将分配到相同的proximity UUID。为这条“链带”设计的专用应用程序将会在后台使用这个UUID扫描到这条“链带”中的beacon设备。
major 编号:用于将相关的beacon标识为一组。例如,一个商店中的所有beacon将会分配到相同的major编号。通过这种方式,应用程序就能够知道顾客位于哪一家商店。
minor 标号:用于标识特定的beacon设备。例如一个商店中的每一个beacon设备都拥有唯一的minor编号,这样你才能够知道顾客位于商店中的哪个位置。
Measuring distance(测量距离)
最后一个值, TX power ,用于确定你和beacon之间距离有多近。根据这个值不但可以获得粗略的信息(比如靠近/远离/不在范围内等),也可以获取精确到米的距离(当然你也可以转换为以步为单位的距离)。那么如何实现?
TX power (上面例子中为0xC6=198,根据2的补码测得256-198=-58dBm)是距离设备1米测得的信号强度值(RSSI- Received Signal Strength Indication,接收到的信号强弱指标)。假如接收到的信号强度减弱了,那么我们可能在远离。只要知道1米距离的RSSI,以及当前的RSSI(我们可以从接收到的信号中一块获取到这些信息),那么计算出当前的距离是可能的。IOS已经实现了个这个功能,对于其它平台需要自己手动编码计算 。
一个简单的测距函数
protected static double calculateAccuracy(int txPower, double rssi) { if (rssi == 0) { return -1.0; // if we cannot determine accuracy, return -1. }double ratio = rssi * 1.0 / txPower; if (ratio < 1.0) { return Math.pow(ratio, 10); } else { double accuracy = (0.89976) * Math.pow(ratio, 7.7095) + 0.111; return accuracy; } }

在使用蓝牙时需要加权限

关键代码如下
package cn.edu.zafu.ble; import android.app.Activity; import android.bluetooth.BluetoothAdapter; import android.bluetooth.BluetoothDevice; import android.bluetooth.BluetoothManager; import android.content.Context; import android.content.Intent; import android.os.Bundle; import android.util.Log; public class MainActivity extends Activity { private BluetoothAdapter mBluetoothAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE); mBluetoothAdapter = bluetoothManager.getAdapter(); if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) { Intent enableBluetooth = new Intent( BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(enableBluetooth, 1); } mBluetoothAdapter.startLeScan(mLeScanCallback); }private BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() { @Override public void onLeScan(final BluetoothDevice device, final int rssi, final byte[] scanRecord) { int startByte = 2; boolean patternFound = false; // 寻找ibeacon while (startByte < = 5) { if (((int) scanRecord[startByte + 2] & 0xff) == 0x02 & & // Identifies // an // iBeacon ((int) scanRecord[startByte + 3] & 0xff) == 0x15) { // Identifies // correct // data // length patternFound = true; break; } startByte++; } // 如果找到了的话 if (patternFound) { // 转换为16进制 byte[] uuidBytes = new byte[16]; System.arraycopy(scanRecord, startByte + 4, uuidBytes, 0, 16); String hexString = bytesToHex(uuidBytes); // ibeacon的UUID值 String uuid = hexString.substring(0, 8) + "-" + hexString.substring(8, 12) + "-" + hexString.substring(12, 16) + "-" + hexString.substring(16, 20) + "-" + hexString.substring(20, 32); // ibeacon的Major值 int major = (scanRecord[startByte + 20] & 0xff) * 0x100 + (scanRecord[startByte + 21] & 0xff); // ibeacon的Minor值 int minor = (scanRecord[startByte + 22] & 0xff) * 0x100 + (scanRecord[startByte + 23] & 0xff); String ibeaconName = device.getName(); String mac = device.getAddress(); int txPower = (scanRecord[startByte + 24]); Log.d("BLE",bytesToHex(scanRecord)); Log.d("BLE", "Name:" + ibeaconName + "\nMac:" + mac + " \nUUID:" + uuid + "\nMajor:" + major + "\nMinor:" + minor + "\nTxPower:" + txPower + "\nrssi:" + rssi); Log.d("BLE","distance:"+calculateAccuracy(txPower,rssi)); } } }; static final char[] hexArray = "0123456789ABCDEF".toCharArray(); private static String bytesToHex(byte[] bytes) { char[] hexChars = new char[bytes.length * 2]; for (int j = 0; j < bytes.length; j++) { int v = bytes[j] & 0xFF; hexChars[j * 2] = hexArray[v > > > 4]; hexChars[j * 2 + 1] = hexArray[v & 0x0F]; } return new String(hexChars); }protected static double calculateAccuracy(int txPower, double rssi) { if (rssi == 0) { return -1.0; // if we cannot determine accuracy, return -1. }double ratio = rssi * 1.0 / txPower; if (ratio < 1.0) { return Math.pow(ratio, 10); } else { double accuracy = (0.89976) * Math.pow(ratio, 7.7095) + 0.111; return accuracy; } } }

至此,本文也就结束,所谓初步,就是获取ibeacon模块的基本信息。
【android蓝牙4.0(BLE)开发之ibeacon初步】源码下载
http://download.csdn.net/detail/sbsujjbcy/8503507



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