带有线程的Python串行端口-冻结计算机

Question

Okay, time for another question/post...

So currently i am trying to develop a simple python program that has a webkit/ webpage view and a serial port interface.. Not that it should matter, but this is also running on a raspberry pi.

The following code works fine.. But it will freeze the system as soon as i uncomment the serial port line that you can see commented out.

The day has been long and this one for some reason has my brain fried.. Python is not my strongest point, but mind you this is just a quick test script for now... Yes i have used google and other resources...

#!/usr/bin/env python

import sys
import serial
import threading
import time

from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4.QtWebKit import *

sURL = ""
sURL2 = ""
objSerial = serial.Serial(0)

def SerialLooper():
    global objSerial
    if objSerial.isOpen() == True:
        print("is_responding")
        #objSerial.write("is_responding")
        time.sleep(10)
        SerialLooper()

class TestCLASS(object):
    def __init__(self):
        global sURL
        global sURL2
        global objSerial
        objSerial = serial.Serial(0)
        sURL = "http://localhost/tester"
        app = QApplication(sys.argv)
        webMain = QWebView()
        webMain.loadFinished.connect(self.load_finished)
        webMain.load(QUrl(sURL))
        webMain.show()
        thread = threading.Thread(target=SerialLooper)
        thread.start()
        sys.exit(app.exec_())

    def load_finished(boolNoErrors):
        global sURL
        print("Url - " + sURL)
        #something here
        #something else here

newObjClass = TestCLASS()

EDIT Futher on this, it appears its not the multithreading but the serial.write()

Answer 1

It has been a while since I used serial, but IIRC it is not threadsafe (on Windows at least). You are opening the port in the main thread and performing a write in another thread. It's a bad practice anyway. You might also consider writing a simple single-threaded program to see if the serial port is actually working.

PS Your program structure could use some work. You only need one of the global statements (global objSerial), the rest do nothing. It would be better to get rid of that one, too.

And the recursive call to SerialLooper() will eventually fail when the recursion depth is exceeded; why not just use a while loop...

def SerialLooper():
    while objSerial().isOpen():  # Drop the == True
        # print something 
        # write to the port
        # Sleep or do whatever