Show Raspberry Pi GPIO readings with PyQt [duplicate] - python-3.x

Question

My python script need to change one object lcd_p1 every time the function wait_thread_v1 is call every second by a thread t1, but how do this? I don't know how to access this object inside the function? Anyone can help?
vazao1 = 12
global pulses_v1
pulses_v1 = 0
GPIO.setmode(GPIO.BCM)
GPIO.setup(vazao1, GPIO.IN)
class Window(QWidget):
def __init__(self):
super().__init__()
self.setGeometry(50, 50, 640, 480)
self.setWindowTitle("Programa")
self.initUI()
def initUI(self):
self.lcd_v1 = QLCDNumber(self)
self.lcd_v1.display(0)
self.lcd_v1.setDigitCount(4)
self.lcd_v1.setFixedWidth(180)
self.lcd_v1.setFixedHeight(80)
self.lcd_v1.move(60,320)
def count_pulses_v1(channel):
global pulses_v1
pulses_v1 += 1
def wait_thread_v1():
global pulses_v1
while True:
time.sleep(1)
print("Pulsos total de vazão 1: "+str(pulses_v1))
#Window.initUI.self.lcd_p1.display(100)
pulses_v1 = 0
GPIO.add_event_detect(vazao1, GPIO.FALLING, callback=count_pulses_v1)
t1 = Thread(target=wait_thread_v1, name='thread_01', args=())
t1.start()
if __name__ == '__main__':
app = QApplication(sys.argv)
window = Window()
window.show()
sys.exit(app.exec())

Answer 1

You cannot and should not modify the GUI from a secondary thread as indicated by the docs since Qt does not guarantee that it works besides that it is unnecessary to create a new thread. In this case it is better to create a QObject that emits the signal when the callback is invoked since it is thread-safe, and then connect that signal to a slot that increases the pulses, then use a QTimer to implement the logic of the thread.
import sys
from PyQt5.QtCore import pyqtSignal, pyqtSlot, QObject, QTimer
from PyQt5.QtWidgets import QApplication, QLCDNumber, QWidget
import RPi.GPIO as GPIO
class Window(QWidget):
def __init__(self):
super().__init__()
self.pulses = 0
self.setGeometry(50, 50, 640, 480)
self.setWindowTitle("Programa")
self.initUI()
timer = QTimer(self, timeout=self.on_timeout, interval=1000)
timer.start()
def initUI(self):
self.lcd_v1 = QLCDNumber(self)
self.lcd_v1.display(0)
self.lcd_v1.setDigitCount(4)
self.lcd_v1.setFixedWidth(180)
self.lcd_v1.setFixedHeight(80)
self.lcd_v1.move(60, 320)
#pyqtSlot()
def falling_slot(self):
self.pulses += 1
#pyqtSlot()
def on_timeout(self):
self.lcd_v1.display(self.pulses)
self.pulses = 0
class GPIOManager(QObject):
fallingSignal = pyqtSignal()
def __init__(self, parent=None):
super().__init__(parent)
pin = 12
GPIO.setmode(GPIO.BCM)
GPIO.setup(pin, GPIO.IN)
GPIO.add_event_detect(pin, GPIO.FALLING, callback=self.falling_callback)
def falling_callback(self, channel):
# This method is called in the thread where GPIOs are monitored.
self.fallingSignal.emit()
if __name__ == "__main__":
app = QApplication(sys.argv)
window = Window()
window.show()
manager = GPIOManager()
manager.fallingSignal.connect(window.falling_slot)
sys.exit(app.exec())