Get data from BLE with Python Bleak

Suitable For

有 Python 基本概念或程式語言基礎

Prerequisite

Software
- Python 3.8 or above ( 2024/01/26: Bleak 0.21.1 only support Python 3.8 or above )
Hardware
- BLE device
- Computer with BLE support ( 支援 Bluetooth 4.0 以上的電腦 )

Code

本篇利用 Python 的 Bleak 套件來取得資料，並直接解析資料

Bleak 是 MIT 授權的開源套件，其相關的文件放在 Reference 1-3

本篇所有程式碼都放在 Github

安裝 Bleak
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pip install bleak

import Bleak 並且掃描周遭裝置

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import asyncio
from bleak import BleakScanner, BleakClient

async def main():
    # Scan for all available devices
    devices = await BleakScanner.discover()

    for device in devices:
        print(device)

asyncio.run(main())

執行結果如下圖:

會找到所有周遭的裝置，並且列出裝置地址與裝置名稱，後續可以利用這兩個資訊來建立連線

透過指定裝置地址或裝置名稱來建立連線

指定裝置名稱

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import asyncio
from bleak import BleakScanner

target_device_name = "YOUR_DEVICE_NAME"

async def main():
    # Scan for all available devices
    devices = await BleakScanner.discover()

    for device in devices:
        if device.name == target_device_name:
            print(f"Found target device: {device.name}, {device.address}")

asyncio.run(main())

指定裝置地址

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import asyncio
from bleak import BleakScanner

target_address = "YOUR_DEVICE_ADDRESS"

async def main():
    # Scan for all available devices
    devices = await BleakScanner.discover()

    for device in devices:
        if device.address == target_address:
            print(f"Found target device: {device.name}, {device.address}")

asyncio.run(main())

建立連線後，表列出此裝置所支援的所有 Services 和 Characteristics

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import asyncio
from bleak import BleakScanner, BleakClient

target_device_name = "YOUR_DEVICE_NAME"

async def main():
    # Scan for all available devices
    devices = await BleakScanner.discover()

    for device in devices:
        if device.name == target_device_name:
            print(f"Found target device: {device.name}, {device.address}")

            # Connect to the target device
            async with BleakClient(device) as client:
                print(f"Connected: {client.is_connected}")

                services = await client.get_services()
                # Print all services and characteristics
                for service in services:
                    print(f"Service: {service.uuid}")
                    for char in service.characteristics:
                        print(f"\tCharacteristic: {char.uuid}")

asyncio.run(main())

執行結果如下圖:

上圖表示的是此裝置所支援的所有 Services 和 Characteristics，僅有列出 UUID，此 UUID 是上一篇文章中提到的 ATT 中的 Attribute Types，代表服務類型

具體的服務類型需要參考藍牙或裝置規格書

藍牙規格書

依照藍牙規格書可以對應出上圖中的服務類型:

類型	UUID	名稱
Service	0x1800	Generic Access service
Characteristic	0x2A00	Device Name
Characteristic	0x2A01	Appearance
Characteristic	0x2A04	Peripheral Preferred Connection Parameters
Service	0x1801	Generic Attribute service
Service	0x180A	Device Information service
Characteristic	0x2a23	System ID
Characteristic	0x2a24	Model Number String
Characteristic	0x2a25	Serial Number String
Characteristic	0x2a26	Firmware Revision String
Characteristic	0x2a27	Hardware Revision String
Characteristic	0x2a28	Software Revision String
Characteristic	0x2a29	Manufacturer Name String
Characteristic	0x2a2a	IEEE 11073-20601 Regulatory Certification Data List
Characteristic	0x2a50	PnP ID

透過指定 Service 和 Characteristic 來取得資料

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import asyncio
from bleak import BleakScanner, BleakClient

target_device_name = "YOUR_DEVICE_NAME"
DEVICE_INFO_SERVICE_UUID = "0000180a-0000-1000-8000-00805f9b34fb"
MANUFACTURER_NAME_CHAR_UUID = "00002a29-0000-1000-8000-00805f9b34fb"
MODEL_NUMBER_CHAR_UUID = "00002a24-0000-1000-8000-00805f9b34fb"

async def main():
    # Scan for all available devices
    devices = await BleakScanner.discover()

    for device in devices:
        if device.name == target_device_name:
            print(f"Found target device: {device.name}, {device.address}")

            async with BleakClient(device) as client:
                print(f"Connected: {client.is_connected}")

                services = await client.get_services()
                print("Reading device information...")

                for service in services:
                    if service.uuid == DEVICE_INFO_SERVICE_UUID:
                        print(f"Device Information Service: {service.uuid}")
                        for char in service.characteristics:
                            if char.uuid == MANUFACTURER_NAME_CHAR_UUID:
                                manufacturer_name = await client.read_gatt_char(char)
                                print(f"\tManufacturer Name: {manufacturer_name}")
                            elif char.uuid == MODEL_NUMBER_CHAR_UUID:
                                model_number = await client.read_gatt_char(char)
                                print(f"\tModel Number: {model_number}")

asyncio.run(main())

執行結果如下圖:

後續可以透過 client.read_gatt_char(char) 來取得資料，並且透過 client.write_gatt_char(char, data) 來寫入資料