Plot Not Updating Qt Gui And Pyqtgraph Python

As the title says, my plot does not update. The objetive is to initiate the plot when the button is clicked. The window pops up and the axis are formed, but no curve is plotted. i

Solution 1:

It is recommended not to modify the code provided by Qt Designer since if you want to modify the design you will have to rewrite your code, besides the Ui_MainWindow class is not a widget but a class that is used to fill some widget, so I recommend deleting the changes .

On the other hand is not suitable to run with a timer with a range of 0, since it does not allow updating the GUI, on the other hand the reading of the serial is blocking, so a possible solution is to use QThread, and use a signal to update the data in the GUI thread.

classUi_MainWindow(object):
    ...

classArduinoThread(QtCore.QThread):
    dataChanged = QtCore.pyqtSignal(str)
    def__init__(self, *args, **kwargs):
        QtCore.QThread.__init__(self, *args, **kwargs)
        self.raw = serial.Serial('com4', 9600)
        self.raw.close()
        self.raw.open()

    defrun(self):
        whileTrue:
            datos_array = self.raw.readline().decode().split(',')
            if datos_array:
                datos = datos_array[0]
            self.dataChanged.emit(datos)
            QtCore.QThread.msleep(10)

classMainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def__init__(self, *args, **kwargs):
        QtWidgets.QMainWindow.__init__(self, *args, **kwargs)
        self.setupUi(self)
        self.BotonInicio.clicked.connect(self.start)
        self.m = 0defupdate_plot(self, dato):
        if self.m > 99:
            self.y1 = np.zeros(100, dtype=float)
            self.m = 0else:
            self.y1[self.m] = dato
            self.m += 1
        self.curva1.setData(self.y1)

    defstart(self):
        thread = ArduinoThread(self)
        thread.dataChanged.connect(self.update_plot)
        thread.start()
        self.win = pg.GraphicsWindow()
        self.win.setWindowTitle('Datos de arduino')
        self.p1 = self.win.addPlot()
        self.p1.setYRange(0, 1024, padding=0)
        self.curva1 = self.p1.plot()
        self.y1 = np.zeros(100, dtype=float)


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

As you can see, I have made some changes to improve the application as verifications, use variables when necessary, etc.

---

Although a way compatible with Qt is to use QSerialPort that emits the readyRead signal when there is a new data:

from PyQt5 import QtCore, QtGui, QtWidgets, QtSerialPort
....

classMainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def__init__(self, *args, **kwargs):
        QtWidgets.QMainWindow.__init__(self, *args, **kwargs)
        self.setupUi(self)
        self.BotonInicio.clicked.connect(self.start)

    defupdate_plot(self):
        while self.ser.canReadLine():
            line = bytearray(self.ser.readLine()).decode()
            self.processLine(line)

    defprocessLine(self, line):
        datos_array = line.strip().split(',')
        if datos_array:
            dato = datos_array[0]
            if self.m > 99:
                self.y1 = np.zeros(100, dtype=float)
                self.m = 0else:
                self.y1[self.m] = dato
                self.m += 1

            self.curva1.setData(self.y1)

    defstart(self):
        self.ser = QtSerialPort.QSerialPort("com4", self)
        self.ser.setBaudRate(9600)
        self.ser.readyRead.connect(self.update_plot)
        self.ser.open(QtSerialPort.QSerialPort.ReadOnly)
        self.win = pg.GraphicsWindow()
        self.win.setWindowTitle('Datos de arduino')
        self.p1 = self.win.addPlot()
        self.p1.setYRange(0, 1024, padding=0)
        self.curva1 = self.p1.plot()
        self.y1 = np.zeros(100, dtype=float)


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())