ValueError:无法将字符串转换为浮点数:使用 matplotlib、arduino 和 pyqt5 时 [英] ValueError: could not convert string to float: when using matplotlib, arduino and pyqt5

问题描述

虽然使用 arduino 代码(也将引脚 13 连接到 arduino uno 中的 A0)以更改值

While using an arduino code (also connecting pin 13 to A0 in an arduino uno) to have changing values

int PinOutput = 13;
int PinInput = A0;
int inph;
int inpl;

void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(PinInput, INPUT);
pinMode(PinOutput, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
inpl = analogRead(PinInput)/4;
Serial.println(inpl);
analogWrite(PinOutput,255);
delay(1000);
inph = analogRead(PinInput)/4;
Serial.println(inph);
analogWrite(PinOutput,0);
delay(1000);
}

然后尝试使用python读取代码，

And then trying to read the code with python using,

from PyQt5 import QtCore, QtGui, QtWidgets
import serial
import time
import sys 
import random 
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg
import matplotlib
matplotlib.use('Qt5Agg')

ser = serial.Serial('COM3', baudrate = 9600, timeout = 1)
time.sleep(3)
class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(325, 237)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setGeometry(QtCore.QRect(110, 20, 61, 16))
        self.label.setObjectName("label")
        self.textEdit = QtWidgets.QTextEdit(self.centralwidget)
        self.textEdit.setGeometry(QtCore.QRect(90, 60, 104, 71))
        self.textEdit.setObjectName("textEdit")
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(100, 150, 75, 23))
        self.pushButton.setObjectName("pushButton")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 325, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)


    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "test window"))
        self.label.setText(_translate("MainWindow", "pyqt5 tests"))
        self.pushButton.setText(_translate("MainWindow", "test button"))
        self.pushButton.clicked.connect(self.label_change)  
        self.thread_start = MyThread()
        self.thread_start.ard_signal.connect(self.label.setText)        
        self.thread_start.start()
    
    def label_change(self):
        self.pushButton.setText('Button Clicked!')
        self.textEdit.setText('taco')

class MainWindowm(QtWidgets.QMainWindow):

    def __init__(self, *args, **kwargs):
        super(MainWindowm, self).__init__(*args, **kwargs)

        self.canvas = MplCanvas(self, width=5, height=4, dpi=100)
        self.setCentralWidget(self.canvas)

        n_data = 50
        self.xdata = list(range(n_data))
        self.ydata = [random.randint(0, 10) for i in range(n_data)]

        self._plot_ref = None
        self.update_plot()

        self.show()

        self.timer = QtCore.QTimer()
        self.timer.setInterval(1000)
        self.timer.timeout.connect(self.update_plot)
        self.timer.start()

    def update_plot(self):

        time.sleep(1)
        self.ydata = self.ydata[1:] +  [float(ser.readline().decode().split('\r\n')[0].strip())]
        self.canvas.axes.cla()  
        self.canvas.axes.plot(self.xdata, self.ydata, 'r')

        self.canvas.draw()

class MyThread(QtCore.QThread):
    ard_signal = QtCore.pyqtSignal(str)

    
    def __init__(self):
        QtCore.QThread.__init__(self)
        
    def run(self):
        counter = 0
        while 1:
            time.sleep(1)
            self.ard_signal.emit(str(ser.readline().decode().split('\r\n')[0]))
            counter += 1
        sys.exit()

if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    w = MainWindowm()

    sys.exit(app.exec_())

如果我将 arduino 代码中的延迟设置为 delay(1) 然后我看不到任何错误(至少，只要我尝试等待，大约 20 分钟)，并且显示在绘图和窗口中的值为 0 或 255.但是延迟为 1000 时，我会收到类似的错误，

If I set the delays in the arduino code to delay(1) then I don't see any error (at least, not for as long as I've tried waiting, about 20 minutes), and values that show up in the plot and window are 0 or 255. But with the delay at 1000, I get errors like,

Traceback (most recent call last):

  File "C:\Documents\ardmatlibpyqt5.py", line 141, in update_plot
    self.ydata = self.ydata[1:] +  [float(ser.readline().decode().split('\r\n')[0].strip())]

ValueError: could not convert string to float: '25\r0'

或者像这样的结尾

ValueError: 无法将字符串转换为浮点数:'255\r0'

窗口中显示的值可能是 255 或 0 或什么都没有的数字，或者它们的一部分(使用的数字，而不是中间的数字).所以当 arduino 运行得很快时，没有错误，但是当它很慢时，就会有.我试图让多个东西同时运行，pyqt5 与 arduino 和 matplotlib.我已经让所有这些单独运行(如 pyqt5 和 arduino，matplotlib 和 arduino，arduino 和 pyqt5)，如果我只是用 arduino 运行 pyqt5，打印出值，则没有错误.任何有关可能导致错误的想法都会有所帮助，谢谢.

with the value showing up in the window being digits that may be like 255 or 0 or nothing, or parts of them (the digits used, not numbers in between). So when the arduino is running fast, there are no errors, but when it's slow, there are. I'm trying to get multiple things running at once, pyqt5 with arduino and matplotlib. I've gotten all of these to run separately together (like pyqt5 and arduino, matplotlib and arduino, arduino and pyqt5), there are no errors if I just run pyqt5 with arduino, printing out values. Any ideas on what could be causing the error would be helpful, thanks.

推荐答案

不要使用 pyserial 而是 QSerialPort 因为它提供了通过信号通知是否有数据的优点，因此您将避免使用计时器或 time.sleep().

Do not use pyserial but QSerialPort since it offers the advantage of notifying if there is data or not through signals and thus you will avoid using timers or time.sleep().

import random
import sys

from PyQt5 import QtCore, QtGui, QtWidgets, QtSerialPort

from matplotlib.figure import Figure
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg


class MainWindowm(QtWidgets.QMainWindow):
    def __init__(self, *args, **kwargs):
        super(MainWindowm, self).__init__(*args, **kwargs)

        self.canvas = FigureCanvasQTAgg(Figure(figsize=(5, 4), dpi=100))
        self.setCentralWidget(self.canvas)

        self.axes = self.canvas.figure.subplots()

        n_data = 50
        self.xdata = list(range(n_data))
        self.ydata = [random.randint(0, 10) for i in range(n_data)]

        self.serial_port = QtSerialPort.QSerialPort("COM3")
        self.serial_port.setBaudRate(QtSerialPort.QSerialPort.Baud9600)
        self.serial_port.errorOccurred.connect(self.handle_error)
        self.serial_port.readyRead.connect(self.handle_ready_read)
        self.serial_port.open(QtCore.QIODevice.ReadWrite)

    def handle_ready_read(self):
        while self.serial_port.canReadLine():
            codec = QtCore.QTextCodec.codecForName("UTF-8")
            line = codec.toUnicode(self.serial_port.readLine()).strip().strip('\x00')
            try:
                print(line)
                value = float(line)
            except ValueError as e:
                print("error", e)
            else:
                self.update_plot(value)

    def handle_error(self, error):
        if error == QtSerialPort.QSerialPort.NoError:
            return
        print(error, self.serial_port.errorString())

    def update_plot(self, value):
        self.ydata = self.ydata[1:] + [value]
        self.axes.cla()
        self.axes.plot(self.xdata, self.ydata, "r")
        self.canvas.draw()


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindowm()
    w.show()

    sys.exit(app.exec_())

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