小编Mar*_*ark的帖子

我正在研究由 Pratik Desai（令人讨厌的聪明人）编写的“Python Programming for Arduino”一书。

我陷入了练习，学生正在学习实现一个滑块，该滑块可以改变连接到引脚的 LED 的强度。我标记了代码不能正常工作的地方。

代码是：

import tkinter
from pyfirmata import ArduinoMega
from time import sleep

port = '/dev/ttyACM0'
board = ArduinoMega(port)
sleep(5)
lenPin = board.get_pin('d:11:o')

top = tkinter.Tk()
top.title('Specify time using Entry')
top.minsize(300, 30)
timePeriodEntry = tkinter.Entry(top, bd=5, width=25)
brightnessScale = tkinter.Scale(top, from_=0, to=100, 
orient=tkinter.HORIZONTAL)
brightnessScale.grid(column=2, row=2)
tkinter.Label(top, text='Time (seconds)').grid(column=1, row=1)
tkinter.Label(top, text='Brightness (%)').grid(column=1, row=2)

def onStartPress():
    time_period = timePeriodEntry.get()
    time_period = float(time_period)
    ledBrightness = brightnessScale.get()
    ledBrightness = float(ledBrightness)
    startButton.config(state=tkinter.DISABLED)
    lenPin.write(ledBrightness / 100.0) # this …