real time graph is freezing in raspberry pi

[Jan Sebastian]

I write an application that displays random number in real time graph, it run perfectly on windows but when I try it on raspberry pi it alwarys stop updating the graph, but the proses in the python shell is still running generate a rundom number and the program didn't.

Any idea, how to fix it?

the example of my code:

from PyQt4 import QtCore,QtGui,uic

from PyQt4.QtCore import QTime, QTimer

import sys

import time

import threading

from pyqtgraph import ViewBox, PlotWidget

#import pyqtgraph as pg

from pyqtgraph.Qt import QtCore, QtGui

import numpy as np

from blupblupshub import BlumBlumShub

from TimeAxisItem import TimeAxisItem

from collections import deque

import random

qtCreatorFile = "mejaGetar2.ui"

Ui_MainWindow,QtBaseClass = uic.loadUiType(qtCreatorFile)

class MyApp(QtGui.QTabWidget,Ui_MainWindow):

    akselerasi = 0

    threads = []

    threads2 = []

    varGraph1 = object 

    aa = False

    def __init__(self):

        QtGui.QTabWidget.__init__(self)

        Ui_MainWindow.__init__(self)

        self.setupUi(self)

        self.akselerasi.setMinimum(0)

        self.akselerasi.setMaximum(30)

        self.akselerasi.setValue(0)

        

        self.akselerasi.sliderReleased.connect(self.getThread)

        self.graph1.setRange(xRange=None, yRange=[-1, 1 ])

        self.graph1.setLabel('bottom', 'time', 's')

        self.graph1.showGrid(x=True, y=True)

        #self.graph1.setLab('bottom',TimeAxisItem(orientation='bottom'))

        self.graph1.setMouseEnabled(x=False, y=False)

        MyApp.varGraph1 = self.graph1

        self.l1.setText(str(self.akselerasi.value()))

        #self.currentChanged.connect(self.forceCloseThread)

        

    def getThread(self):

        

        if self.sender() == self.akselerasi:

            MyApp.akselerasii = int(self.akselerasi.value())

        if MyApp.akselerasii > 0:

            

            thread1 = DynamicThread("akselerasi")

            

            if MyApp.aa == True:

                print("second")

                minRange = int(self.akselerasi.value()) * -1

                self.graph1.setRange(xRange=None, yRange=[minRange, int(self.akselerasi.value()) ])

                thread1.trigrer(MyApp.akselerasii)

                

            else:

                thread1.trigrer(MyApp.akselerasii)

                MyApp.threads2.append(thread1)

                minRange = int(self.akselerasi.value()) * -1

                self.graph1.setRange(xRange=None, yRange=[minRange, int(self.akselerasi.value()) ])

                MyApp.aa = True

                

                print("first")

                thread1.start()

        else:

            for t in MyApp.threads2:

                MyApp.aa = False

                t.stop()

                self.graph1.clear()

        

class DynamicThread(threading.Thread,MyApp):

    intAkselerasi = 0

    ruuun = False

    def __init__(self,sub):

        threading.Thread.__init__(self)

        

        self.subject = sub

        

    def trigrer(self,num):

        DynamicThread.intAkselerasi = num

        

    def run(self):

        listData = []

        a = 0

        count = 0

        test = 0

        t = QTime()

        t.start()

        dataGraph = deque(maxlen=20)

        x1 = []

        y1 = []

        

        print("starting " + self.subject)

        dynamicGenerator = BlumBlumShub()

        curve = MyApp.varGraph1.plot(pen=(255,0,0))

        while DynamicThread.ruuun == True:

            if DynamicThread.intAkselerasi > 0:

                minus = DynamicThread.intAkselerasi *-1

                data = random.randint(minus,DynamicThread.intAkselerasi)

                

                dataGraph.append({'x': t.elapsed(), 'y': data})

                x1 = [item['x'] for item in dataGraph]

                y1 = [item['y'] for item in dataGraph]

                curve.setData(x=x1, y=y1)

                print("test: ",data)

                print("\n")

                a = a + 1

                time.sleep(0.5)

                

            else:

                DynamicThread.ruuun = False

                print("stop")

                break

        print("stoping " + self.subject)

        dataGraph = []

        x1 = []

        y1 = []

        

    def start(self):

        DynamicThread.ruuun = True

        super(DynamicThread,self).start()

    def stop(self):

        DynamicThread.ruuun = False

if __name__ == "__main__":

    app = QtGui.QApplication(sys.argv)

    window = MyApp()

    window.show()

    sys.exit(app.exec_())

[Luke Campagnola]

My first thought is that the example is attempting to perform GUI operations from a thread. Qt does not support this behavior, so that probably explains the freezing. If you search a little, there are many articles and examples that discuss how to properly use threads with Qt.

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[Jan Sebastian]

so, can I using this: https://groups.google.com/forum/#!topic/pyqtgraph/haiJsGhxTaQ as a example for my code if I didn't want using qTimer?

[Jeremy Webster]

To add to Luke's point

1. I suspect you should use QThread instead of python's threading.Thread, since QThread will provide signals and slots that will easily allow the thread to communicate back and forth with the GUI.

2.  Some tutorials will tell you to subclass QThread, but that seems to be bad advice, the correct way is to create a worker object, then add it to a QThread.

3. (For a C++ based explanation, but one that applies to pyqt as well https://mayaposch.wordpress.com/2011/11/01/how-to-really-truly-use-qthreads-the-full-explanation/ )

4. For a pyqt4 example, check out Matthew Levine's solution in this stackoverflow post... ( https://stackoverflow.com/questions/6783194/background-thread-with-qthread-in-pyqt? )

[Patrick]

I had an issue similar to this which I solved while still using Python's threads/events etc rather than QThread (which was easier and less disruptive to my existing code). The trick was to make your own pyqtSignal and slots and only use those for communicating between the Python data acquisition thread and the Qt GUI thread when updates are required.

Demo example:

https://groups.google.com/d/msg/pyqtgraph/ajykxBvysEc/e1V8lvZSCgAJ

[Jan Sebastian]

Thank you for all of your explanation and examples, it's work

Pada Selasa, 15 Mei 2018 23.17.41 UTC+7, Luke Campagnola menulis:

[Jan Sebastian]

Thank you for all of your explanation and examples, it's work