蓝牙GATT数据在传输过程中损坏

Question

我正在使用noble来使用我的bleno外设。当数据缓冲区到达我高贵的Characteristic.read()时，我在onReadRequest()回调中返回的数据缓冲区不知何故被损坏了。我在onReadRequest()中的回调之前转储缓冲区，当我在Characteristic.read()中获得它时，我立即转储它

消费者

...
Characteristic.read((err, data) => {
      if (err) {
        reject(err);
      } else {     
        console.log(data);
      }
    });
...

生产者

...
const bleno = require('bleno');

const flags = {
    a: 1 << 0,
    b: 1 << 1,
    c: 1 << 2
  },
  numBytesInReturnData = 18,
  supportedFlags = flags.a | flags.b | flags.c,
  accelPrecision = Math.pow(10, 5),
  bPrecision = Math.pow(10, 3);

module.exports = class DataCharacteristic extends bleno.Characteristic {
  constructor(pin) {
    super({
      uuid: '1234',
      properties: ['read'],
      descriptors: [new bleno.Descriptor({
        uuid: '2901',
        value: 'blah'
      })]
    });
    this._hardware = hardware;
    this._hasData = false;
    this._dataBuffer = new Buffer.allocUnsafe(numBytesInReturnData).fill(0);
  }

  onReadRequest(offset, callback) {
    if (!offset) {
      this._hasData = false;
      this._dataBuffer.fill(0);
      Promise.all([
          this._hardware.getA),
          this._hardware.getB(),
          this._hardware.getC(),
        ]).then((responses) => {
          this._dataBuffer.writeUInt8(supportedFlags, 0);

          this._dataBuffer.writeUInt8(responses[0], 1);
          this._dataBuffer.writeInt32LE(responses[0] * aPrecision, 2, true);
          this._dataBuffer.writeInt32LE(responses[2].x * accelPrecision, 6, true); //accel
          this._dataBuffer.writeInt32LE(responses[2].y * accelPrecision, 10, true);
          this._dataBuffer.writeInt32LE(responses[2].z * accelPrecision, 14, true);

          console.log(this._dataBuffer);

          this._hasData = true;
          callback(this.RESULT_SUCCESS, this._dataBuffer);
        })
        .catch(err => {
          console.error('Error when reading hardware data', err);
          callback(this.RESULT_UNLIKELY_ERROR);
        });
    } else if (this._hasData) { //reading a second time for rest of data
      callback(this.RESULT_SUCCESS, this._dataBuffer.slice(offset));
    } else {
      callback(this.RESULT_ATTR_NOT_LONG);
    }
  }
}

生产者输出

<Buffer 07 00 00 00 00 00 c2 c9 ff ff e4 2c 00 00 1c 47 0f 00>

消费热潮

<Buffer 07 00 00 00 00 00 c2 c9 ff ff 5f 34 00 00 5f 43 0f 00>

正如您所看到的，只有部分缓冲区被损坏。这一切为什么要发生？

Answer 1

您是否可以在外围设备通知或指示后立即阅读？如果是这样，那么传递给读取回调的数据可能实际上是来自上一次通知或指示的数据。请参阅本期here。