发送buffer信息成功，蓝牙设备能正确接收信息，但是writeBleCharacteristic api 一直返回错误：

后测试固定数据写入，使用iphone6p手机依然写入失败

    let buffer= new ArrayBuffer(4)
    let dataView = new DataView(buffer)
    dataView.setUint8(0, 0x1b)
    dataView.setUint8(1, 0x84)
    dataView.setUint8(2, 0x00)
    dataView.setUint8(3, 0x84)      
    wx.writeBLECharacteristicValue({
        deviceId: this._deviceId,
        serviceId: this._serviceId,
        characteristicId: this._characteristicId,
        value: buffer,
        success: (res) => {
          this.setPrcess(` uuid:${this._characteristicId}写入二进制数据成功： ${res.errMsg}`)
          console.log('writeBLECharacteristicValue success', res.errMsg)
        },
        fail: (res) => {
          this.setPrcess(` uuid:${this._characteristicId}写入二进制数据失败`)
          this.setData({ writeErrorMsg: `写入失败：${e.errMsg}` })
        }