[python-win32] Python - connexion to serial port

[Schoeni, Yann]

Ok guys,

I'm gonna try to give you a full explanation.

I thought it would be a great idea to keep it open during the application life time for one reason.

My webserver (running on windows) got a Velleman VM8090 module plugged in with a usb cable, my serial port is virtual.

Working process :


1)      A QR code is read by a QR code reader

2)      The QR code is paste into an input field and send to a controller

3)      The controller checks the validity of the code in agreement with a database

4)      If the code is approuved the controller use shell_exec to open a python command line

5)      A python script is call with args like this :

Python C:\temp\gate.py on


6)      Every time the script is launch, it open the serial port, send the command depending on the argument and close it.

7)      Sometimes, the script return < The Serial port is already open >, and a delay is identified. Below the function that open the port :

def open_device() :
    try:
        print("Opening serial port")
        ser = serial.Serial(
            port='COM200',
            baudrate=19200,
            parity=serial.PARITY_NONE,
            stopbits=serial.STOPBITS_ONE,
            bytesize=serial.EIGHTBITS,
        )
    except IOError:
        print("Serial port already open !")
        ser.close()
        ser.open()
    return ser


8)      Because of this delay I was just thinking about keeping the serial port open while the application is running.

What do you guys think ? $

Best wishes !

Yann Schoeni
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