Vérifiez simplement la communication série avec tk

# -*- coding: utf-8 -*-
import tkinter as tk
import serial as sl
import time
import datetime as dt


class App(tk.Frame):
    finFlag = True
    serial = None
    def __init__(self, master=None):
        super().__init__(master)
        self.master.protocol('WM_DELETE_WINDOW', self.On_Close) 
        #Ici, vous pouvez décider arbitrairement du paramètre de communication série
        self.serial = sl.Serial('COM7', 19200, timeout=0)
        while( self.serial.is_open is False):
            time.sleep(100)
            
        self.createPage()
        
        self.after(10, self.readData)
        
    def createPage(self):
        self.page1 = tk.Frame(self.master)
        self.page1.pack(pady=5, padx=30)
        
        self.timelabel = tk.Label(self.page1)
        self.timelabel.grid(column=0, row=0)
        self.timelabel['text'] = dt.datetime.now().strftime("%Y/%m/%d %H:%M:%S")
        
        self.label = tk.Label(self.page1, font=("",20), relief='ridge')
        self.label.grid(column=1, row=0)
        self.label['text'] = '00.0A'
        
           
    def readData(self):
        line = None
        self.timelabel['text'] = dt.datetime.now().strftime("%Y/%m/%d %H:%M:%S")
        if ( self.serial.is_open):
            line = self.serial.readline()
            line = line.strip().decode('utf-8')

            
        if( (line is not None) and (line != '')):

            print(line)
            
            self.label['text'] = line
            
        if ( self.finFlag ):
            self.after(10, self.readData)
        
    def On_Close(self):
        self.finFlag = False
        self.serial.close()
        self.master.destroy()

def main():
    root = tk.Tk()
    app = App(root)
    app.mainloop()

if __name__ == '__main__':
    main()