Question

下面是在GUI上创建按钮以控制秒表的代码。我想问一下是否有人知道如何修改代码，以便我们可以在覆盆子PI上使用GPIO引脚作为输入（意味着我们有3个按钮组件来控制秒表运行）。

我唯一知道的是我们必须将RPi.GPIO作为GPIO，GPIO.setmode（GPIO.BOARD）和GPIO.setup（）引入GPIO引脚。任何人都可以帮助我???

from Tkinter import *
import time

class StopWatch(Frame):  
    """ Implements a stop watch frame widget. """                                                                
    def __init__(self, parent=None, **kw):        
        Frame.__init__(self, parent, kw)
        self._start = 0.0        
        self._elapsedtime = 0.0
        self._running = 0
        self.timestr = StringVar()               
        self.makeWidgets()      

    def makeWidgets(self):                         
        """ Make the time label. """
        l = Label(self, textvariable=self.timestr)
        self._setTime(self._elapsedtime)
        l.pack(fill=X, expand=NO, pady=2, padx=2)                      

    def _update(self): 
        """ Update the label with elapsed time. """
        self._elapsedtime = time.time() - self._start
        self._setTime(self._elapsedtime)
        self._timer = self.after(50, self._update)

    def _setTime(self, elap):
        """ Set the time string to Minutes:Seconds:Hundreths """
        minutes = int(elap/60)
        seconds = int(elap - minutes*60.0)
        hseconds = int((elap - minutes*60.0 - seconds)*100)                
        self.timestr.set('%02d:%02d:%02d' % (minutes, seconds, hseconds))

    def Start(self):                                                     
        """ Start the stopwatch, ignore if running. """
        if not self._running:            
            self._start = time.time() - self._elapsedtime
            self._update()
            self._running = 1        

    def Stop(self):                                    
        """ Stop the stopwatch, ignore if stopped. """
        if self._running:
            self.after_cancel(self._timer)            
            self._elapsedtime = time.time() - self._start    
            self._setTime(self._elapsedtime)
            self._running = 0

    def Reset(self):                                  
        """ Reset the stopwatch. """
        self._start = time.time()         
        self._elapsedtime = 0.0    
        self._setTime(self._elapsedtime)

def main():

    root = Tk()
    sw = StopWatch(root)
    sw.pack(side=TOP)

    Button(root, text='Start', command=sw.Start).pack(side=LEFT)
    Button(root, text='Stop', command=sw.Stop).pack(side=LEFT)
    Button(root, text='Reset', command=sw.Reset).pack(side=LEFT)
    Button(root, text='Quit', command=root.quit).pack(side=LEFT)

    root.mainloop()

if __name__ == '__main__':
    main()

Answer 1

Makezine建议使用GPIO an extensive tutorial。

您可以在_update方法中轮询按钮值。

if self._running and (GPIO.input(23) ==1):
    self.Stop()

当你的时钟没有运行时，这将不起作用，所以你可能会调整你的逻辑以使你的_update后循环始终在运行（或者创建另一个专用于Pi按钮轮询的后循环）。 / p>

此外，GPIO在另一个线程中提供了waitloop。这是对Makezine的例子的改编，以链接回tkinter（未经测试）。

def relayToTkinter(channel):
    sw.event_generate('<<Start>>', when='tail')

GPIO.add_event_detect(23, GPIO.RISING, callback=relayToTkinter, bouncetime=300)
sw.bind("<<Start>>", lambda event:sw.Start())

event_generate("<<VirtualEvent>>", when='tail')是让另一个线程与主UI线程交互的安全方法。

Raspberry pi GPIO引脚控制Tkinter GUI秒表

1 个答案: