Introduction

This article is a tutorial article for those who want to perform BLE communication of SwitchBot using Bleak on Windows 10. It connects to SwitchBot and sends instruction bytes. The language is python. Also, although SwitchBot is used in this article, it can be used for other BrueTooth devices as BLE communication using Bleak because it only connects and sends instruction bytes. (Probably)

Requirements

Windows10
python 3.7.6
bleak 0.7.1
SwitchBot
Bluetooth_Dongle 5.0 (required if the PC does not have a built-in transmitter / receiver)

SwitchBot It is a switch that can be operated remotely by Bluetooth. There are multiple types, but this time we will use the following SwitchBot https://www.switchbot.jp/bot

BLE communication

BLE (Bluetooth Low Energy) communication is a standard added from Bluetooth version 4.0 that enables communication with Bluetooth devices with low power consumption. I think it is easier to understand this area if you refer to the article of the predecessor. https://houwa-js.co.jp/blog/2018/06/20180629/
https://jellyware.jp/kurage/bluejelly/ble_guide.html

Pyblues cannot be used under Windows environment

If you want to perform BLE communication of SwitchBot under Windows environment, pybluez, which is the main BLE communication library used, cannot be used on Windows. (Reference: https://atatat.hatenablog.com/entry/2020/07/09/003000#3-Bleak%E3%81%AE%E5%88%A9%E7%94%A8) In addition, github for BLE communication on PC is published on SwitchBot, but since it is a code supported only by pyblues, It cannot be used as it is.

Use of Bleak

From this article Since it was said that a module called Bleak can be used for BLE communication under Windows environment, I will use it. Execute the following pip command.

pip install bleak

Find out the MAC address of the SwitchBot

While referring to the Official Document, execute the program to search for nearby Bluetooth devices on your PC.

`Discover.py`


import asyncio
from bleak import discover

async def run():
    devices = await discover()
    for d in devices:
        #Show mac address, name, distance of found device
        print(d.address,d.name,d.rssi)
        print(d)

loop = asyncio.get_event_loop()
loop.run_until_complete(run())

If SwitchBot is found here, the MAC address of SwitchBot will be displayed, so copy it. If you can't find it, download the Bluetooth driver from here and check if the SwitchBot is recognized correctly. In addition, there is a possibility of initial failure of SwitchBot, so it is recommended to perform a connection test from the SwitchBot app provided by the Android / iOS app. The detailed method is described in the quick start guide enclosed with Switchbot.

Connection with SwutchBot

If the MAC address can be obtained, connect to SwitchBot using BLE communication → send a command. The following program is a sample of the created connection and transmission.

`Bleak_Connect_SwitchBot.py`


import asyncio
from bleak import discover

async def run():
import asyncio
from bleak import BleakClient
import time

#switchbot mac address.[Discover.py]Need to find out in
address = " "
#switchbot UUID.Excavated from SwitchBot's github
UUID = "cba20002-224d-11e6-9fb8-0002a5d5c51b"


async def run(address, loop):
    async with BleakClient(address, loop=loop) as client:
        #Pause to prevent synchronization mistakes.
        time.sleep(5)

        #Connection test below.[Connected: False]Is displayed, the connection has failed.
        x = await client.is_connected()
        print("Connected: {0}".format(x))
        #Check the current status of switchbot
        y = await client.read_gatt_char(UUID)
        print(y)
        print("The connection was successful. Please enter the command.\n command → press,on,off,exit")
        while True:
            #Receive input. Change the instruction to be sent for each command. exit if exit
            command = input()
            if command == "press":
                write_byte = bytearray(b'\x57\x01\x00')
            elif command == "on":
                write_byte = bytearray(b'\x57\x01\x01')
            elif command == "off":
                write_byte = bytearray(b'\x57\x01\x02')
            elif command == "exit":
                #[exit]If you enter, it will end in 1 second
                await asyncio.sleep(1.0, loop=loop)
                break
            else:
                print("Please enter the command.\n command → press,on,off,exit")
                continue

            #Send instructions to switchbot
            await client.write_gatt_char(UUID, write_byte)
            #Check the current status of switchbot
            y = await client.read_gatt_char(UUID)
            print(y)
            #Pause due to synchronization error
            time.sleep(2)


#Start communication with switchbot by bleak
loop = asyncio.get_event_loop()
loop.run_until_complete(run(address, loop))

This program waits for input from standard I / O if the connection is successful. You can enter the following command:

press: Switch Bot on / off (b'\ x57 \ x01 \ x00')
on: Turn SwitchBot on (b'\ x57 \ x01 \ x01')
off: Turn off SwitchBot (b'\ x57 \ x01 \ x02')
exit: exit

Switch the instruction byte according to the operation you want to perform, and send the instruction to Switchbot by client.write_gatt_char (UUID, write_byte). If the SwitchBot works correctly, you are successful.

Summary

I explained how to use SwitchBot for BLE communication (python) under Windows environment. The content explained in this article can only connect and send, and I do not yet know how to switch modes of SwtichBot due to my lack of study. In the future, when I find a mode switching method from the official document or github, I would like to add it and describe it in another article.

[]( Github that summarizes the code is here (only the code in this article is available) ) Postscript (2020/09/11): SwitchBot API uses BlueZ, so it could not be used on Windows. https://github.com/RoButton/switchbotpy

[PYTHON] Run SwitchBot on Windows 10 with Bleak