从 BLE 设备读取值

Question

我拥有一条 Polar H10 胸带，它以低功耗蓝牙运行并提供心率和心率变异性。

我想用 Android 应用程序读出这些值。感谢 official BLE tutorial 中的帮助，我能够连接到设备。现在的问题是从设备中读出心率和心率变异性值。每当设备上有一个新值时，我都想读出这个值（并且至少每秒都有一个新值）。

我找到了以下代码片段：

private static double extractHeartRate(
            BluetoothGattCharacteristic characteristic) {

        int flag = characteristic.getProperties();
        Log.d(TAG, "Heart rate flag: " + flag);
        int format = -1;
        // Heart rate bit number format
        if ((flag & 0x01) != 0) {
            format = BluetoothGattCharacteristic.FORMAT_UINT16;
            Log.d(TAG, "Heart rate format UINT16.");
        } else {
            format = BluetoothGattCharacteristic.FORMAT_UINT8;
            Log.d(TAG, "Heart rate format UINT8.");
        }
        final int heartRate = characteristic.getIntValue(format, 1);
        Log.d(TAG, String.format("Received heart rate: %d", heartRate));
        return heartRate;
    }



private static Integer[] extractBeatToBeatInterval(
            BluetoothGattCharacteristic characteristic) {

        int flag = characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT8, 0);
        int format = -1;
        int energy = -1;
        int offset = 1; // This depends on hear rate value format and if there is energy data
        int rr_count = 0;

        if ((flag & 0x01) != 0) {
            format = BluetoothGattCharacteristic.FORMAT_UINT16;
            Log.d(TAG, "Heart rate format UINT16.");
            offset = 3;
        } else {
            format = BluetoothGattCharacteristic.FORMAT_UINT8;
            Log.d(TAG, "Heart rate format UINT8.");
            offset = 2;
        }
        if ((flag & 0x08) != 0) {
            // calories present
            energy = characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT16, offset);
            offset += 2;
            Log.d(TAG, "Received energy: {}"+ energy);
        }
        if ((flag & 0x16) != 0){
            // RR stuff.
            Log.d(TAG, "RR stuff found at offset: "+ offset);
            Log.d(TAG, "RR length: "+ (characteristic.getValue()).length);
            rr_count = ((characteristic.getValue()).length - offset) / 2;
            Log.d(TAG, "RR length: "+ (characteristic.getValue()).length);
            Log.d(TAG, "rr_count: "+ rr_count);
            if (rr_count > 0) {
                Integer[] mRr_values = new Integer[rr_count];
                for (int i = 0; i < rr_count; i++) {
                    mRr_values[i] = characteristic.getIntValue(
                            BluetoothGattCharacteristic.FORMAT_UINT16, offset);
                    offset += 2;
                    Log.d(TAG, "Received RR: " + mRr_values[i]);
                }
                return mRr_values;
            }
        }
        Log.d(TAG, "No RR data on this update: ");
        return null;
    }

假设我已连接到设备，我如何使用它来提取心率和 r-r 间隔（心跳间隔）？如果有人能举一个简短的例子，我会很高兴。另外，我想使用一项服务，以便它在后台运行，我可以做其他工作并且消耗更少的电池。但是该服务应该具有最高优先级，这样它就不会被杀死。

在 extractBeatToBeatInterval() 方法中有一个 int offset = 1; 的描述

This depends on hear rate value format and if there is energy data

我不明白这个offest的意思。我应该使用什么偏移值？

其次，如果连接中断，我希望收到通知以便我可以处理它（例如显示消息）。我该怎么做？

Answer 1

关于这件事我可以帮你做几件事。对于连接中断，你可以这样处理

public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            if (newState == BluetoothGatt.STATE_CONNECTED) {
                Log.e(Constants.TAGGattConnectThread, "Connected to the GATT Server " + status + " " +newState);
                Log.e(Constants.TAGGattConnectThread, "Attempting to discover services");
                bluetoothGatt.discoverServices();
            }
            else if(newState == BluetoothGatt.STATE_DISCONNECTED)
            {
                Log.e(Constants.TAGGattConnectThread,"Band disconnected");
               //Write you disconnect handling code here
            }

您还可以在连接到 Gatt

时将“自动连接”选项设置为 'True'

bluetoothGatt = bluetoothDevice.connectGatt(context, true, bluetoothGattCallback);

对于创建服务，您可以创建一个 Sticky 服务，它会自行重启，除非强制停止。

从 BLE 设备读取值

Reading values from BLE device

android

bluetooth-lowenergy

android-bluetooth