Run motor till stop button is pressed but have the ability to switch between windows

Question

I wish to make a motor control app. I have 3 windows, which are as follows (unfortunately I cannot upload pictures yet, can I upload them some other way ):

So, what I want to do is when a user clicks then "GO" button the motor rotates and when the user clicks the "STOP" button the motor stops. After the "GO" button has been pressed I would also like to go to a different window such as the window in the top and bottom picture.

However, the GUI freezes after clicking the "GO" button. Is there a way that doesn't freeze the GUI and allow me to get the desired functionality?

#! usr/bin/env python

import threading
import serial
import time
import tkinter as tk




System_State_is_Run=False
class DH_Corp_SCADA2(tk.Tk):
    def __init__(self, *args,**kwargs):
              tk.Tk.__init__(self, *args, *kwargs)
              container=tk.Frame(self)
              container.pack(side="top",fill="both",expand=True)
              container.grid_rowconfigure(0,weight=10)
              container.grid_columnconfigure(0,weight=10)
              self.frames={}
              for F in (HomePage, ControlPage, Speed1Page):
              frame=F(container,self)
              self.frames[F]=frame
              frame.grid(row=0, column=0, sticky="nsew")

              self.show_frame(HomePage)

    def show_frame(self,cont):
        frame=self.frames[cont]
        frame.tkraise()

class HomePage(tk.Frame):
      def __init__(self, parent, controller):
         tk.Frame.__init__(self, parent)
         someLabel=tk.Label(self,text='Welcome to the AGC SCADA....')
         AGC_Control=tk.Button(self,text='AGC Control & Parameters',
              command=lambda:controller.show_frame(ControlPage))
         AGC_Speed=tk.Button(self,text='Monitor Speed',command=lambda:
                               controller.show_frame(Speed1Page))
         Exit_Button=tk.Button(self, text='Exit',command=close_window)
             someLabel.grid(row=0, sticky="W")
         AGC_Control.grid(row=2, column=1, sticky="EW",padx=2,pady=2)
         AGC_Speed.grid(row=3,column=1, sticky="EW", padx=2,pady=2)
         Exit_Button.grid(row=4,column=1, sticky="EW",padx=2,pady=2)


    class ControlPage(tk.Frame):
          def __init__(self, parent, controller):
          tk.Frame.__init__(self, parent)
          someLabel1=tk.Label(self,text='From this page you may change p.')
          Go_Home1=tk.Button(self,text='Home Page',command=lambda:controller.show_frame(HomePage))
          AGC_Speed=tk.Button(self,text='Monitor Speed',command=lambda:controller.show_frame(Speed1Page))
          Exit_Button=tk.Button(self, text='Exit',command=close_window)
          Go_Button=tk.Button(self,text='GO',command=System_State_is_RunXY1)
          Stop_Button=tk.Button(self,text='STOP', command=System_State_is_RunXY2)
           someLabel1.grid(row=0, sticky="W")
          Go_Button.grid(row=2,column=1, sticky="EW",padx=2,pady=2)
          Stop_Button.grid(row=3,column=1, sticky="EW",padx=2,pady=2)
          Go_Home1.grid(row=4, column=1, sticky="EW",padx=2,pady=2)
          AGC_Speed.grid(row=5,column=1, sticky="EW", padx=2,pady=2)
          Exit_Button.grid(row=6,column=1, sticky="EW",padx=2,pady=2)




   class Speed1Page(tk.Frame):
         def __init__(self, parent, controller):
         tk.Frame.__init__(self, parent)
         someLabel2=tk.Label(self,text='From this page you can monitor speed parameter in channel 1 or left motor.')
         Go_Home2=tk.Button(self,text='Home  Page',command=lambda
                            :controller.show_frame(HomePage))
         AGC_Control=tk.Button(self,text='AGC Control & Parameters',command=
                            lambda:controller.show_frame(ControlPage))
         Exit_Button=tk.Button(self, text='Exit',command=close_window)
         someLabel2.grid(row=0, sticky="W")
         Go_Home2.grid(row=2,column=1, sticky="EW", padx=2,pady=2)
         AGC_Control.grid(row=3, column=1, sticky="EW",padx=2,pady=2)
         Exit_Button.grid(row=4,column=1, sticky="EW",padx=2,pady=2)        



def System_State_is_RunXY1():
    global System_State_is_Run
    System_State_is_Run=True
    print(System_State_is_Run)#check if System_State_is_Run changes
    running_car()

def System_State_is_RunXY2():
    global System_State_is_Run
    System_State_is_Run=False
    print(System_State_is_Run)#check if System_State_is_Run changes
    running_car()

def running_car():
     print(System_State_is_Run)#check if System_State_is_Run changes
     if System_State_is_Run==True:
         motor_run_callback()
         running_car()
    else:
         motor_off_callback()
         return


def motor_run_callback():# set motor speed to 25rpm
    ser = serial.Serial('COM6',115200,timeout=0)
    time.sleep(0.025)
    ser.write(bytes('!G 1 250\r','utf-8'))
    ser.close()
    return

def motor_off_callback(): #set motor speed to 0
    ser = serial.Serial('COM6',115200,timeout=0)
    time.sleep(0.025)
    ser.write(bytes('!G 1 0\r','utf-8'))
    ser.close()


def close_window(): 
    app.destroy()


app=DH_Corp_SCADA2()            
app.mainloop()

Answer 1

• The button calls System_State_is_RunXY1.
• System_State_is_RunXY1 sets System_State_is_Run to True, and then calls running_car().
  • running_car() sees that System_State_is_Run is True, and calls motor_run_callback(), and then calls itself again.
  • running_car() sees that System_State_is_Run is True, and calls motor_run_callback(), and then calls itself again.
  • running_car() sees that System_State_is_Run is True, and calls motor_run_callback(), and then calls itself again.
  • ... and so on

Nowhere in that logic do you allow the GUI to process events. Since tkinter is single threaded, you must allow the event loop to process events for the GUI to remain responsive.

Whether you are visualizing it or not, you are effectively doing an animation. Animation is typically done with the after method. You call a function which does a tiny bit of work (animates the motor, monitors a port, etc.) and then calls itself again in a few milliseconds. In the time after it finished but before it is called again, the event loop has a chance to handle events such as a click on a "Stop" button.

For a slightly longer description see https://stackoverflow.com/a/11505034/7432