sendData(str) {
    let that = this;
    let dataBuffer = new ArrayBuffer(str.length)
    let dataView = new DataView(dataBuffer)
    for (var i = 0; i < str.length; i++) {
      dataView.setUint8(i, str.charAt(i).charCodeAt())
    }
    let dataHex = that.ab2hex(dataBuffer);
    this.writeDatas = that.hexCharCodeToStr(dataHex);
    wx.writeBLECharacteristicValue({
      deviceId: that.connectedDeviceId,
      serviceId: that.services[0].uuid,
      characteristicId: that.notifyCharacteristicsId,
      value: dataBuffer,
      success: function (res) {
        console.log('发送的数据：' + that.writeDatas)
        console.log('message发送成功')
        
      },
      fail: function (res) {
        console.log('message发送失败')
      }
    })
  }
})

我这边显示发送成功，但是我觉得实际上外设没有接受到数据，所以它也不会有回调结果，不知道这个是不是设备的原因