[SOLVED] PyQt5 The QLCNumber doesnt update

Issue

i want to make a program that count pulses then it go through some equation and display it in the gui . This my main.py

import sys
import time
import RPi.GPIO as GPIO
import PyQt5
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from mainwindow import Ui_MainWindow
GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.IN, pull_up_down = GPIO.PUD_UP)
 
class MainWindow(QMainWindow):
 # access variables inside of the UI's file
 def __init__(self):
     super().__init__()
     self.mainwindow = Ui_MainWindow()
     self.mainwindow.setupUi(self)
     self.i=100
     self.flow = 0
     self.flowliter = 0
     self.totalflow=0

     
     self.mainwindow.lcdNumber.display(self.i)
     self.mainwindow.lcdNumber_2.display(self.i)  
     self.show()
     
 
     self.mainwindow.startbttn.clicked.connect(lambda: self.pressedstartButton())
     self.mainwindow.stopbttn.clicked.connect(lambda: self.pressedstopButton())
     
 
 def pressedstartButton(self):
     print ("Pressed On!")
     self.data()
 
 def pressedstopButton(self):
     print ("Pressed Off!")
     
 def data(self) :
     global count
     count = 0

     def countPulse(channel):
      global count
      if start_counter == 1:
          count = count+1

     GPIO.add_event_detect(FLOW_SENSOR, GPIO.FALLING, callback=countPulse)

     while True:
        try:
         start_counter = 1
         time.sleep(1)
         start_counter = 4

         self.flow = (10 * 60)
         self.flowliter= (self.flow/60)
         self.totalflow += self.flowliter
         print("%d"% (count))
         print ("The flow is: %.3f Liter/min" % (self.flow))
         print ("The flowliter is: %.3f Liter" % (self.flowliter))
         print ("The volume is: %.3f Liter" % (self.totalflow))
         self.mainwindow.lcdNumber.display(self.flow)
         self.mainwindow.lcdNumber_2.display(self.flowliter)
         count = 0
         time.sleep(1)
        except KeyboardInterrupt:
         print ('\ncaught keyboard interrupt!, bye')
         GPIO.cleanup()
         sys.exit()


def main():
     app = QApplication(sys.argv)
     form = MainWindow()
     form.show()
     sys.exit(app.exec_())
 
if __name__ == "__main__":
    main()

the lcdnumber doesnt update in the gui but the self.flow update in the shell and i want display the value in the gui but i dont know which one suitable qtablewidget or qtextbroswer this code should count the pulse from the gpio 18 and show the flow in the gui.

Solution

You should not use time-consuming functions as they block the eventloop and the consequence is to freeze the GUI. In this case, you should not use an infinite loop or time.sleep but a QTimer is enough.

import sys
import RPi.GPIO as GPIO

from PyQt5.QtWidgets import *
from PyQt5.QtCore import *

from mainwindow import Ui_MainWindow


FLOW_SENSOR = 18


class MainWindow(QMainWindow):
    pinSignal = pyqtSignal()

    def __init__(self):
        super().__init__()
        self.mainwindow = Ui_MainWindow()
        self.mainwindow.setupUi(self)
        self.i = 100
        self.flow = 0
        self.flowliter = 0
        self.totalflow = 0

        self.mainwindow.lcdNumber.display(self.i)
        self.mainwindow.lcdNumber_2.display(self.i)
        self.show()

        self.mainwindow.startbttn.clicked.connect(self.pressedstartButton)
        self.mainwindow.stopbttn.clicked.connect(self.pressedstopButton)

        self.start_counter = False
        self.count = 0

        self.timer = QTimer(self, interval=1000, timeout=self.execute_every_second)
        self.pinSignal.connect(self.handle_pin_signal)

    def pressedstartButton(self):
        print("Pressed On!")
        GPIO.add_event_detect(FLOW_SENSOR, GPIO.FALLING, callback = lambda *args: self.pinSignal.emit())
        self.execute_every_second()
        self.timer.start()

    def pressedstopButton(self):
        print("Pressed Off!")
        self.timer.stop()
        GPIO.remove_event_detect(FLOW_SENSOR)

    def handle_pin_signal(self):
        if self.start_counter:
            self.count += 1

    def execute_every_second(self):
        if not self.start_counter:
            self.flow = 10 * 60
            self.flowliter = self.flow / 60
            self.totalflow += self.flowliter
            print("%d" % (self.count))
            print("The flow is: %.3f Liter/min" % (self.flow))
            print("The flowliter is: %.3f Liter" % (self.flowliter))
            print("The volume is: %.3f Liter" % (self.totalflow))
            self.mainwindow.lcdNumber.display(self.flow)
            self.mainwindow.lcdNumber_2.display(self.flowliter)
            self.count = 0
        self.start_counter = not self.start_counter


def main():
    GPIO.setmode(GPIO.BCM)
    GPIO.setup(FLOW_SENSOR, GPIO.IN, pull_up_down=GPIO.PUD_UP)

    app = QApplication(sys.argv)
    form = MainWindow()
    form.show()
    ret = app.exec_()

    GPIO.cleanup()

    sys.exit(ret)


if __name__ == "__main__":
    main()

Answered By - eyllanesc

Answer Checked By - David Goodson (WPSolving Volunteer)