Example sharing of how WeChat applet implements Bluetooth

https://mp.weixin.qq.com/debug/wxadoc/dev/api/bluetooth.html#wxgetconnectedbluethoothdevicesobject

/**
 * 搜索设备界面
 */
Page({
 data: {
  logs: [],
  list:[],
 },
  onLoad: function () {
  console.log('onLoad')
var that = this;
// const SDKVersion = wx.getSystemInfoSync().SDKVersion || '1.0.0'
// const [MAJOR, MINOR, PATCH] = SDKVersion.split('.').map(Number)
// console.log(SDKVersion);
// console.log(MAJOR);
// console.log(MINOR);
// console.log(PATCH);

// const canIUse = apiName => {
//  if (apiName === 'showModal.cancel') {
//   return MAJOR >= 1 && MINOR >= 1
//  }
//  return true
// }

// wx.showModal({
//  success: function(res) {
//   if (canIUse('showModal.cancel')) {
//    console.log(res.cancel)
//   }
//  }
// })
   //获取适配器
   wx.openBluetoothAdapter({
   success: function(res){
    // success
    console.log("-----success----------");
     console.log(res);
     //开始搜索
    wx.startBluetoothDevicesDiscovery({
 services: [],
 success: function(res){
  // success
   console.log("-----startBluetoothDevicesDiscovery--success----------");
   console.log(res);
 },
 fail: function(res) {
  // fail
   console.log(res);
 },
 complete: function(res) {
  // complete
   console.log(res);
 }
})


   },
   fail: function(res) {
     console.log("-----fail----------");
    // fail
     console.log(res);
   },
   complete: function(res) {
    // complete
     console.log("-----complete----------");
     console.log(res);
   }
  })

   wx.getBluetoothDevices({
    success: function(res){
     // success
     //{devices: Array[11], errMsg: "getBluetoothDevices:ok"}
     console.log("getBluetoothDevices");
     console.log(res);
     that.setData({
     list:res.devices
     });
     console.log(that.data.list);
    },
    fail: function(res) {
     // fail
    },
    complete: function(res) {
     // complete
    }
   })

 },
 onShow:function(){


 },
  //点击事件处理
 bindViewTap: function(e) {
   console.log(e.currentTarget.dataset.title);
   console.log(e.currentTarget.dataset.name);
   console.log(e.currentTarget.dataset.advertisData);

  var title = e.currentTarget.dataset.title;
  var name = e.currentTarget.dataset.name;
   wx.redirectTo({
    url: '../conn/conn?deviceId='+title+'&name='+name,
    success: function(res){
     // success
    },
    fail: function(res) {
     // fail
    },
    complete: function(res) {
     // complete
    }
   })
 },
})

/**
 * 连接设备。获取数据
 */
Page({
  data: {
    motto: 'Hello World',
    userInfo: {},
    deviceId: '',
    name: '',
    serviceId: '',
    services: [],
    cd20: '',
    cd01: '',
    cd02: '',
    cd03: '',
    cd04: '',
    characteristics20: null,
    characteristics01: null,
    characteristics02: null,
    characteristics03: null,
    characteristics04: null,
    result,

  },
  onLoad: function (opt) {
    var that = this;
    console.log("onLoad");
    console.log('deviceId=' + opt.deviceId);
    console.log('name=' + opt.name);
    that.setData({ deviceId: opt.deviceId });
    /**
     * 监听设备的连接状态
     */
    wx.onBLEConnectionStateChanged(function (res) {
      console.log(`device ${res.deviceId} state has changed, connected: ${res.connected}`)
    })
    /**
     * 连接设备
     */
    wx.createBLEConnection({
      deviceId: that.data.deviceId,
      success: function (res) {
        // success
        console.log(res);
        /**
         * 连接成功，后开始获取设备的服务列表
         */
        wx.getBLEDeviceServices({
          // 这里的 deviceId 需要在上面的 getBluetoothDevices中获取
          deviceId: that.data.deviceId,
          success: function (res) {
            console.log('device services:', res.services)
            that.setData({ services: res.services });
            console.log('device services:', that.data.services[1].uuid);
            that.setData({ serviceId: that.data.services[1].uuid });
            console.log('--------------------------------------');
            console.log('device设备的id:', that.data.deviceId);
            console.log('device设备的服务id:', that.data.serviceId);
            /**
             * 延迟3秒，根据服务获取特征 
             */
            setTimeout(function () {
              wx.getBLEDeviceCharacteristics({
                // 这里的 deviceId 需要在上面的 getBluetoothDevices
                deviceId: that.data.deviceId,
                // 这里的 serviceId 需要在上面的 getBLEDeviceServices 接口中获取
                serviceId: that.data.serviceId,
                success: function (res) {
                  console.log('000000000000' + that.data.serviceId);
                  console.log('device getBLEDeviceCharacteristics:', res.characteristics)
                  for (var i = 0; i < 5; i++) {
                    if (res.characteristics[i].uuid.indexOf("cd20") != -1) {
                      that.setData({
                        cd20: res.characteristics[i].uuid,
                        characteristics20: res.characteristics[i]
                      });
                    }
                    if (res.characteristics[i].uuid.indexOf("cd01") != -1) {
                      that.setData({
                        cd01: res.characteristics[i].uuid,
                        characteristics01: res.characteristics[i]
                      });
                    }
                    if (res.characteristics[i].uuid.indexOf("cd02") != -1) {
                      that.setData({
                        cd02: res.characteristics[i].uuid,
                        characteristics02: res.characteristics[i]
                      });
                    } if (res.characteristics[i].uuid.indexOf("cd03") != -1) {
                      that.setData({
                        cd03: res.characteristics[i].uuid,
                        characteristics03: res.characteristics[i]
                      });
                    }
                    if (res.characteristics[i].uuid.indexOf("cd04") != -1) {
                      that.setData({
                        cd04: res.characteristics[i].uuid,
                        characteristics04: res.characteristics[i]
                      });
                    }
                  }
                  console.log(&#39;cd01= &#39; + that.data.cd01 + &#39;cd02= &#39; + that.data.cd02 + &#39;cd03= &#39; + that.data.cd03 + &#39;cd04= &#39; + that.data.cd04 + &#39;cd20= &#39; + that.data.cd20);
                  /**
                   * 回调获取 设备发过来的数据
                   */
                  wx.onBLECharacteristicValueChange(function (characteristic) {
                    console.log(&#39;characteristic value comed:&#39;, characteristic.value)
                    //{value: ArrayBuffer, deviceId: "D8:00:D2:4F:24:17", serviceId: "ba11f08c-5f14-0b0d-1080-007cbe238851-0x600000460240", characteristicId: "0000cd04-0000-1000-8000-00805f9b34fb-0x60800069fb80"}
                    /**
                     * 监听cd04cd04中的结果
                     */
                    if (characteristic.characteristicId.indexOf("cd01") != -1) {
                      const result = characteristic.value;
                      const hex = that.buf2hex(result);
                      console.log(hex);
                    }
                    if (characteristic.characteristicId.indexOf("cd04") != -1) {
                      const result = characteristic.value;
                      const hex = that.buf2hex(result);
                      console.log(hex);
                      that.setData({ result: hex });
                    }

                  })
                  /**
                   * 顺序开发设备特征notifiy
                   */
                  wx.notifyBLECharacteristicValueChanged({
                    deviceId: that.data.deviceId,
                    serviceId: that.data.serviceId,
                    characteristicId: that.data.cd01,
                    state: true,
                    success: function (res) {
                      // success
                      console.log(&#39;notifyBLECharacteristicValueChanged success&#39;, res);
                    },
                    fail: function (res) {
                      // fail
                    },
                    complete: function (res) {
                      // complete
                    }
                  })
                  wx.notifyBLECharacteristicValueChanged({
                    deviceId: that.data.deviceId,
                    serviceId: that.data.serviceId,
                    characteristicId: that.data.cd02,
                    state: true,
                    success: function (res) {
                      // success
                      console.log(&#39;notifyBLECharacteristicValueChanged success&#39;, res);
                    },
                    fail: function (res) {
                      // fail
                    },
                    complete: function (res) {
                      // complete
                    }
                  })
                  wx.notifyBLECharacteristicValueChanged({
                    deviceId: that.data.deviceId,
                    serviceId: that.data.serviceId,
                    characteristicId: that.data.cd03,
                    state: true,
                    success: function (res) {
                      // success
                      console.log(&#39;notifyBLECharacteristicValueChanged success&#39;, res);
                    },
                    fail: function (res) {
                      // fail
                    },
                    complete: function (res) {
                      // complete
                    }
                  })

                  wx.notifyBLECharacteristicValueChanged({
                    // 启用 notify 功能
                    // 这里的 deviceId 需要在上面的 getBluetoothDevices 或 onBluetoothDeviceFound 接口中获取
                    deviceId: that.data.deviceId,
                    serviceId: that.data.serviceId,
                    characteristicId: that.data.cd04,
                    state: true,
                    success: function (res) {
                      console.log(&#39;notifyBLECharacteristicValueChanged success&#39;, res)
                    }
                  })

                }, fail: function (res) {
                  console.log(res);
                }
              })
            }
              , 1500);
          }
        })
      },
      fail: function (res) {
        // fail
      },
      complete: function (res) {
        // complete
      }
    })
  },

  /**
   * 发送 数据到设备中
   */
  bindViewTap: function () {
    var that = this;
    var hex = &#39;AA5504B10000B5&#39;
    var typedArray = new Uint8Array(hex.match(/[\da-f]{2}/gi).map(function (h) {
      return parseInt(h, 16)
    }))
    console.log(typedArray)
    console.log([0xAA, 0x55, 0x04, 0xB1, 0x00, 0x00, 0xB5])
    var buffer1 = typedArray.buffer
    console.log(buffer1)
    wx.writeBLECharacteristicValue({
      deviceId: that.data.deviceId,
      serviceId: that.data.serviceId,
      characteristicId: that.data.cd20,
      value: buffer1,
      success: function (res) {
        // success
        console.log("success 指令发送成功");
        console.log(res);
      },
      fail: function (res) {
        // fail
        console.log(res);
      },
      complete: function (res) {
        // complete
      }
    })

  },
  /**
   * ArrayBuffer 转换为 Hex
   */
  buf2hex: function (buffer) { // buffer is an ArrayBuffer
    return Array.prototype.map.call(new Uint8Array(buffer), x => (&#39;00&#39; + x.toString(16)).slice(-2)).join(&#39;&#39;);
  }
})