从 react-native-ble-plx 中的 GATT 特征值获取权重

Question

我正在开发一个 react-native 应用程序，它获取支持蓝牙的体重秤 (MI SCALE2) 的重量值。（我对蓝牙一无所知。）

//版本

"react-native": "0.66.1",

"react-native-ble-plx": "https://github.com/below/react-native-ble-plx",

当我上秤时，我能够得到这些值。

# feature
{"data": [33, 0, 0, 0], "type": "Buffer"}

# Weight
{"data": [2, 156, 74, 178, 7, 1, 7, 22, 33, 1], "type": "Buffer"}
{"data": [2, 156, 74, 178, 7, 1, 7, 22, 33, 1], "type": "Buffer"}
{"data": [2, 156, 74, 178, 7, 1, 7, 22, 33, 1], "type": "Buffer"}
{"data": [2, 156, 74, 178, 7, 1, 7, 22, 33, 2], "type": "Buffer"}
{"data": [2, 156, 74, 178, 7, 1, 7, 22, 33, 2], "type": "Buffer"}
{"data": [34, 156, 74, 178, 7, 1, 7, 22, 33, 2], "type": "Buffer"}
{"data": [162, 156, 74, 178, 7, 1, 7, 22, 33, 6], "type": "Buffer"}

看了几个地方的Q&A，知道需要结合特征的值和权重数组的值

我想知道如何从我的结果中获取重量值，例如“94.9kg，95.5kg，...”

下面是我写的代码


manager.startDeviceScan(null, null, (error, device) => {
      if (error) {
        console.log('error : ' + error);
        return;
      }

      console.log(device.name);

      if (device.name === 'MI SCALE2') {
        console.log('detected!!');
        manager.stopDeviceScan();
        device
          .connect()
          .then(device => {
            return device.discoverAllServicesAndCharacteristics();
          })
          .then(device => {
            return device.services();
          })
          .then(services => {
            const result = services.filter(id => id.uuid.indexOf('181d') != -1); // 181d is Weight Scale -> org.bluetooth.service.weight_scale;
            return result[0].characteristics();
          })
          .then(characters => {
            const resultDateObject = characters.filter(
              data => data.uuid.indexOf('2a2b') != -1, // 2a2b is Current Time -> org.bluetooth.characteristic.current_time;
            );
            const resultWeightFeature = characters.filter(
              data => data.uuid.indexOf('2a9e') != -1, // 2a9e is Weight Scale Feature -> org.bluetooth.characteristic.weight_scale_feature
            );
            const resultWeight = characters.filter(
              data => data.uuid.indexOf('2a9d') != -1, // 2a9d is Weight Measurement -> org.bluetooth.characteristic.weight_measurement;
            );
            const resultPosition2D = characters.filter(
              data => data.uuid.indexOf('2a2f') != -1, // 2a2f is Position 2D -> org.bluetooth.characteristic.position_2d;
            );
            
            // const DeviceID = resultWeightFeature[0].deviceID;
            // const ServiceUUID = resultWeightFeature[0].serviceUUID;
            // const DateCharacterUUID = resultDateObject[0].uuid;
            // const WeightFeatureCharacterUUID = resultWeightFeature[0].uuid;
            // const WeightCharacterUUID = resultWeight[0].uuid;
            // const PositionCharacterUUID = resultPosition2D[0].uuid;

            resultWeight[0].monitor((error, characteristic) => {
              if (error) {
                console.log('error:::::', error);
                return;
              }
              let your_bytes = Buffer.from(characteristic.value, "base64");
              console.log(your_bytes);
            })
            return resultWeightFeature[0].read();

          }).then(feature => {
            let feature_bytes = Buffer.from(feature.value, "base64");
            console.log('feature.value');
            console.log(feature_bytes);
          })
      }
    });

Answer 1

据我了解您的代码，您的体重秤使用蓝牙 Weight Scale Profile and Weight Scale Service。您在相应特征中找到的数据需要按照Personal Health Devices Transcoding

中的描述进行解释

编辑：您可以在此处找到有关数据结构的更多信息： GATT Specification Supplement 5

示例：

特征([33,0,0,0]) => 0x00000011 => ...00 0010 0001 =>

value	description
1	Time Stamp Supported: True
0	Multiple Users Supported: False
0	BMI Supported: False
0100	Weight Measurement Resolution: Resolution of 0.05 kg or 0.1 lb
000	Height Measurement Resolution: Not specified

体重 = [34, 156, 74, 178, 7, 1, 7, 22, 33, 2] => 0x22 0x9c 0x4a 0xb2 0x07 0x01 0x07 0x16 0x21 0x02

第一个字节是标志字段 => 0x22 => 0010 0010

value	description
0	Measurement Units: SI
1	Time Stamp present: True
0	User ID present: False
0	BMI and Height present: False
0010	Reserved for Future Use

重量以千克为单位，分辨率为 0.005 (uint16) => 0x4a9c => 95,5 kg

时间戳 0xb2 0x07 0x01 0x07 0x16 0x21 0x02

年（uint16）=> 0x07b2 => 1970

月（uint8）=> 0x01 => 1

天（uint8）=> 0x07 => 7

小时（uint8）=> 0x16 => 22

分钟(uint8) => 0x21 => 33

秒（uint8）=> 0x02 => 2

日期 1970-01-07T22:33:02

从 react-native-ble-plx 中的 GATT 特征值获取权重

get weight from GATT characteristics value in react-native-ble-plx

android

android-bluetooth

react-native

react-native-ble-plx