Android BLE 通知丢包

Question

我正在开发一种硬件设备，它通过 BLE 向 Android 应用程序发送连续的数据流。 Android 应用程序接收此数据作为 GATT 通知，然后处理此数据并将其保存到数据库中。

项目详细配置如下:

1. 手机 - Moto E 第一代
2. Android 版本 - Android 5.1 - Lollipop
3. iOS - iPhone 4 和 5，在 iOS 7 和 8 上测试
4. 硬件 - CC2541
5. Connection_Interval:40 ms(在硬件固件中设置)。
6. 每个连接间隔发送的数据包数:4(在硬件固件中设置)。

问题

当数据从硬件设备传输到Android手机上运行的BLE数据捕获应用程序时，没有收到所有数据包。它只收到大约 35-45 个数据包，而预期的数据包数量是 50。

更令人惊讶的是，当我们使用BLE数据包嗅探器时，Android手机嗅探和显示的数据(不完整/不正确的数据)之间存在完美匹配。这让我相信硬件在连接到 Android 手机而不是发送所有数据时表现不同。

当我们将相同的硬件与 iOS BLE 数据捕获应用程序一起使用时，可以正确接收数据。

我对Android中BLE数据捕获的这种行为感到困惑和无能为力。 iOS 设备上的应用程序如何能够正确捕获所有数据，而安卓手机上的应用程序根本无法正确捕获数据？

有没有人在安卓上使用BLE app遇到过这种丢包/数据不正确的问题？欢迎任何意见。非常感谢您的提前帮助。

Android 应用程序使用标准 BLE 代码通过 BLE 连接到设备。我使用的 Android 代码如下所示:

import android.annotation.TargetApi;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattDescriptor;
import android.bluetooth.BluetoothGattService;
import android.bluetooth.BluetoothManager;
import android.bluetooth.BluetoothProfile;
import android.bluetooth.le.BluetoothLeScanner;
import android.bluetooth.le.ScanCallback;
import android.bluetooth.le.ScanFilter;
import android.bluetooth.le.ScanResult;
import android.bluetooth.le.ScanSettings;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.nfc.Tag;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

@TargetApi(21)
public class BLETestActivity extends Activity {
    private BluetoothAdapter mBluetoothAdapter;
    private int REQUEST_ENABLE_BT = 1;
    private Handler mHandler;
    private static final long SCAN_PERIOD = 10000;
    private BluetoothLeScanner mLEScanner;
    private ScanSettings settings;
    private List<ScanFilter> filters;
    private BluetoothGatt mGatt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bletest);
        mHandler = new Handler();
        if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
            Toast.makeText(this, "BLE Not Supported",
                    Toast.LENGTH_SHORT).show();
            finish();
        }
        final BluetoothManager bluetoothManager =
                (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
        mBluetoothAdapter = bluetoothManager.getAdapter();

    }

    @Override
    protected void onResume() {
        super.onResume();
        if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
            Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
        } else {
            if (Build.VERSION.SDK_INT >= 21) {
                Log.i("innnnn","spinnnn - " + Build.VERSION.SDK_INT);
                mLEScanner = mBluetoothAdapter.getBluetoothLeScanner();
                settings = new ScanSettings.Builder()
                        .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
                        .build();
                filters = new ArrayList<ScanFilter>();
            }
            scanLeDevice(true);
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        if (mBluetoothAdapter != null && mBluetoothAdapter.isEnabled()) {
            scanLeDevice(false);
        }
    }

    @Override
    protected void onDestroy() {
        if (mGatt == null) {
            return;
        }
        mGatt.close();
        mGatt = null;
        super.onDestroy();
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REQUEST_ENABLE_BT) {
            if (resultCode == Activity.RESULT_CANCELED) {
                //Bluetooth not enabled.
                finish();
                return;
            }
        }
        super.onActivityResult(requestCode, resultCode, data);
    }

    private void scanLeDevice(final boolean enable) {
        if (enable) {
            mHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    if (Build.VERSION.SDK_INT < 21) {
                        mBluetoothAdapter.stopLeScan(mLeScanCallback);
                    } else {
                        mLEScanner.stopScan(mScanCallback);

                    }
                }
            }, SCAN_PERIOD);
            if (Build.VERSION.SDK_INT < 21) {
                mBluetoothAdapter.startLeScan(mLeScanCallback);
            } else {
                mLEScanner.startScan(filters, settings, mScanCallback);
            }
        } else {
            if (Build.VERSION.SDK_INT < 21) {
                mBluetoothAdapter.stopLeScan(mLeScanCallback);
            } else {
                mLEScanner.stopScan(mScanCallback);
            }
        }
    }


    private ScanCallback mScanCallback = null;/* new ScanCallback() {
        @Override
        public void onScanResult(int callbackType, ScanResult result) {
            Log.i("callbackType", String.valueOf(callbackType));
            Log.i("result", result.toString());
            BluetoothDevice btDevice = result.getDevice();
            connectToDevice(btDevice);
        }

        @Override
        public void onBatchScanResults(List<ScanResult> results) {
            for (ScanResult sr : results) {
                Log.i("ScanResult - Results", sr.toString());
            }
        }

        @Override
        public void onScanFailed(int errorCode) {
            Log.e("Scan Failed", "Error Code: " + errorCode);
        }
    };*/

    private BluetoothAdapter.LeScanCallback mLeScanCallback =
            new BluetoothAdapter.LeScanCallback() {
                @Override
                public void onLeScan(final BluetoothDevice device, int rssi,
                                     byte[] scanRecord) {
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            Log.i("onLeScan", device.toString());
                            connectToDevice(device);
                        }
                    });
                }
            };

    public void connectToDevice(BluetoothDevice device) {
        if (mGatt == null) {
            mGatt = device.connectGatt(this, false, gattCallback);
            scanLeDevice(false);// will stop after first device detection
        }
    }

    private final BluetoothGattCallback gattCallback = new BluetoothGattCallback() {
        @Override
        public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            Log.i("onConnectionStateChange", "Status: " + status);
            switch (newState) {
                case BluetoothProfile.STATE_CONNECTED:
                    Log.i("gattCallback", "STATE_CONNECTED");
                    gatt.discoverServices();
                    break;
                case BluetoothProfile.STATE_DISCONNECTED:
                    Log.e("gattCallback", "STATE_DISCONNECTED");
                    break;
                default:
                    Log.e("gattCallback", "STATE_OTHER");
            }

        }

        @Override
        public void onServicesDiscovered(BluetoothGatt gatt, int status) {
            List<BluetoothGattService> services = gatt.getServices();
           // Log.i("onServicesDiscovered", services.toString());

            for(int i=0;i<services.size();i++) {
                List<BluetoothGattCharacteristic> charList = services.get(i).getCharacteristics();
                for (int j = 0; j < charList.size();j++) {
                    BluetoothGattCharacteristic characteristic = charList.get(j);
                    if (characteristic.getUuid().compareTo(Constants.HEART_DATA_UUID) == 0) {
                        Log.i(BLETestActivity.class.getSimpleName(), "Characteristic UUID is " + characteristic.getUuid());
                        mGatt.setCharacteristicNotification(characteristic, true);
                        BluetoothGattDescriptor descriptor = characteristic.getDescriptor(Constants.HEART_DATA_DESCRIPTOR_UUID);
                        descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
                        mGatt.writeDescriptor(descriptor);
                    }
                }
            }
        }

        public void onCharacteristicChanged(BluetoothGatt gatt,
                                            BluetoothGattCharacteristic characteristic) {
            // Retrieve the byte values
            // Convert them to hex values
            byte[] data = characteristic.getValue();

            // The following array contains data in the follwing form:
            // 0-1 - running counter counts
            // 2-4, 5-7, 8-10  - Sample 1 data for channel 1, channel2 and channel 3
            // 11-13, 14-16, 17-19 - Sample 2 data for channel 1, channel 2 and channel 3

//            Log.i(TAG," ------ " + Thread.currentThread().getId());
            String heartBeatDataInHex = bytesToHex(data);


            // An error packet is received after every 17 samples.
            // Checking to make sure that this is not an error packet

            if (!(heartBeatDataInHex.substring(4, 10).equalsIgnoreCase("FFFFFF") && heartBeatDataInHex.substring(26, 40).equalsIgnoreCase("FFFFFFFFFFFFFF"))) {
                Log.i("testdata", heartBeatDataInHex + " ---- " + Thread.currentThread().getId());
            }
        }

        @Override
        public void onCharacteristicRead(BluetoothGatt gatt,
                                         BluetoothGattCharacteristic
                                                 characteristic, int status) {
            Log.i("onCharacteristicRead", characteristic.toString());
            gatt.disconnect();
        }

    };

    private String bytesToHex(byte[] bytes) {
        final char[] hexArray = "0123456789ABCDEF".toCharArray();
        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);
    }
}

Answer 1

我遇到过类似的问题!我进行了一些测试，确定最小连接间隔为 48 毫秒，android api 级别 18。(connection interval for BLE on Galaxy S3 Android 4.3)。

可能的解决方案:

1. 使连接间隔变慢(小于 48ms)。

2. 从 api 级别 21 到更高级别，您可以更改 CONNECTION_PRIORITY android developer修改间隔连接，但这意味着更多的能量消耗。