如何用Python控制LEGO Wedo 2.0的电机

乐高官方提供的编程工具都是图形化的，这篇文章分享下如何用Python来连接控制LEGO Wedo 2.0中提供的蓝牙主控设备和电机。

学习资源

网上有两篇很有用的文章：

Controlling a WeDo 2.0 motor
WeDo 2.0 – reverse engineering

使用pygattlib可以通过Python和蓝牙低功耗设备通讯。这个库只支持Linux。

命令行工具和开发环境

通过测试发现，Windows的Linux子系统和VMWare虚拟机是不支持的。我最终选了树莓派做开发环境。
使用系统自带的命令行工具可以直接测试蓝牙连接。
扫描设备获取地址：

sudo hcitool -i hci0 lescan
LE Scan ...
98:07:2D:DD:98:56 (unknown)
98:07:2D:DD:98:56 LPF2 Smart Hub

连接设备：

gatttool -I
[                 ][LE]> connect <ble address>

使用Python创建界面控制程序

安装依赖库以及gattlib:

sudo apt-get update
sudo apt-get install libbluetooth-dev bluez bluez-hcidump libboost-python-dev libboost-thread-dev libglib2.0-dev
sudo pip install gattlib

用Tkinter创建界面：

import Tkinter as tk
from gattlib import DiscoveryService
from gattlib import GATTRequester
from time import sleepdef run():global button_runbutton_run.after(DELAY, motor_run)def stop():global button_stopbutton_stop.after(DELAY, motor_stop)def connect():global button_disconnectbutton_disconnect.after(DELAY, smart_hub_connect)def disconnect():global button_disconnectbutton_disconnect.after(DELAY, smart_hub_disconnect)def up():global button_upbutton_up.after(DELAY, motor_up)def down():global button_downbutton_down.after(DELAY, motor_down)root = tk.Tk()
root.title("Lego Wedo 2.0 Motor Control")label = tk.Label(root, fg="dark green", text='N/A')
label.pack()button_connect = tk.Button(root, text='Connect Smart Hub', width=BUTTON_WIDTH, command=connect)
button_connect.pack()button_disconnect = tk.Button(root, text='Disconnect Smart Hub', width=BUTTON_WIDTH, command=disconnect, state='disabled')
button_disconnect.pack()button_run = tk.Button(root, text='Run motor', width=BUTTON_WIDTH, command=run, state='disabled')
button_run.pack()button_up = tk.Button(root, text='Speed up', width=BUTTON_WIDTH, command=up, state='disabled')
button_up.pack()button_down = tk.Button(root, text='Speed down', width=BUTTON_WIDTH, command=down, state='disabled')
button_down.pack()button_stop = tk.Button(root, text='Stop motor', width=BUTTON_WIDTH, command=stop, state='disabled')
button_stop.pack()root.mainloop()

使用DiscoveryService和GATTRequester查找连接设备：

def smart_hub_connect():service = DiscoveryService("hci0")devices = service.discover(2)for address, name in devices.items():if name != '' and 'Smart Hub' in name:label['text'] = addressglobal button_run, button_stop, button_disconnect, reqbutton_connect['state'] = 'disabled'button_run['state'] = 'normal'button_stop['state'] = 'normal'button_disconnect['state'] = 'normal'button_up['state'] = 'normal'button_down['state'] = 'normal'req = GATTRequester(address, True, "hci0")break

运行电机：

def motor_run():global reqif req != None:req.write_by_handle(0x3d, str(bytearray([0x01, 0x01, 0x01, 0x64]))
)

第一个字节代表端口号。主控设备上有两个端口，选择对应的端口号。

通过gatttool也可以查看端口变化：

[98:07:2D:DD:98:56][LE]> char-read-hnd 0015
Characteristic value/descriptor: 01 01 00 01 01 00 00 00 01 00 00 00
[98:07:2D:DD:98:56][LE]> char-read-hnd 0015
Characteristic value/descriptor: 02 01 01 01 01 00 00 00 01 00 00 00

最后一个字节代表速度。可以通过代码动态调节：

MAX_SPEED = 100
MIN_SPEED = 1
SPEED_CHANGE = 4current_speed = 100
req = Nonedef motor_up():global req, current_speedif req != None:if current_speed == MAX_SPEED:returncurrent_speed += SPEED_CHANGEreq.write_by_handle(HANDLE, str(bytearray([0x01, 0x01, 0x01, current_speed])))sleep(WEDO_DELAY)def motor_down():global req, current_speedif req != None:if current_speed == MIN_SPEED:returncurrent_speed -= SPEED_CHANGEreq.write_by_handle(HANDLE, str(bytearray([0x01, 0x01, 0x01, current_speed])))sleep(WEDO_DELAY)

运行程序的时候，如果没有root权限，会出现错误。

运行界面程序需要用gksudo而不是sudo。

在Windows中可以通过SmarTTY来显示远程的GUI。

源码

https://github.com/yushulx/lego-wedo-motor-control