Codesys service disables serial communication

2020-02-27T16:04:56.046000Z

This is the python code that stops working when codesys service is active. Any ideas how to get both of them working in parallel?

\#! /usr/bin/env python3
import RPi.GPIO as GPIO
import serial
ENABLE_PIN  = 18              # The BCM pin number corresponding to GPIO1
SERIAL_PORT = '/dev/ttyUSB0'  # The location of our serial port.  This may
                              # vary depending on OS and RPi version.  The
\#SERIAL_PORT = '/dev/ttyS0'   # RPi 3 has apparently used 'ttyAMA0' for
                              # Bluetooth and assigned 'ttyS0' to the GPIO
                              # serial port, so uncomment the appropriate
                              # SERIAL_PORT definition for your setup.
                              # Failing that, check the output of:
                              #   $ dmesg | grep serial
                              # to get an idea as to where serial has been
                              # assigned to.
                              
def validate_rfid(code):
    # A valid code will be 12 characters long with the first char being
    # a line feed and the last char being a carriage return.
    s = code.decode("ascii")
    if (len(s) == 12) and (s[0] == "\n") and (s[11] == "\r"):
        # We matched a valid code.  Strip off the "\n" and "\r" and just
        # return the RFID code.
        return s[1:-1]
    else:
        # We didn't match a valid code, so return False.
        return False
    
def main():
    # Initialize the Raspberry Pi by quashing any warnings and telling it
    # we're going to use the BCM pin numbering scheme.
    GPIO.setwarnings(False)
    GPIO.setmode(GPIO.BCM)
    # This pin corresponds to GPIO1, which we'll use to turn the RFID
    # reader on and off with.
    GPIO.setup(ENABLE_PIN, GPIO.OUT)
    # Setting the pin to LOW will turn the reader on.  You should notice
    # the green LED light on the reader turn red if successfully enabled.
    print("Enabling RFID reader and reading from serial port: " + SERIAL_PORT)
    GPIO.output(ENABLE_PIN, GPIO.LOW)
    # Set up the serial port as per the Parallax reader's datasheet.
    ser = serial.Serial(baudrate = 2400,
                        bytesize = serial.EIGHTBITS,
                        parity   = serial.PARITY_NONE,
                        port     = SERIAL_PORT,
                        stopbits = serial.STOPBITS_ONE,
                        timeout  = 1)
    # Wrap everything in a try block to catch any exceptions.
    try:
        # Loop forever, or until CTRL-C is pressed.
        while 1:
            # Read in 12 bytes from the serial port.
            data = ser.read(12)
            # Attempt to validate the data we just read.
            code = validate_rfid(data)
            # If validate_rfid() returned a code, display it.
            if code:
                print("Read RFID code: " + code);
    except:
        # If we caught an exception, then disable the reader by setting
        # the pin to HIGH, then exit.
        print("Disabling RFID reader...")
        GPIO.output(ENABLE_PIN, GPIO.HIGH)
        
if __name__ == "__main__":
    main()

Codesys service disables serial communication

2020-02-27T16:04:53.844000Z

Hi all,

I'm very new to codesys (and plc programming), so I'm not only looking for a solution but some explanation would be very welcome

I've installed codesyscontrol service on my Pi, and followed some simple tutorial for making a LED blink with webvisu. (this works fine)
I also have an RFID module attached to the Pi, and (for now) I handle serial communication with a Python script. (later I would like to use the serial data from RFID inside codesys application, but like I said first time with codesys so 1 step at a time)

However, when the codesyscontrol.service is active ( $ systemctl | grep codesys) I cannot read serial data with the Python script anymore. I figured this was because the Pi only has 1 UART, so I got an FTDI USB serial port adapter to handle the serial communication with the RFID module. I edit the Python script to use /tty/USB0 instead of /tty/AMA0, but I have the same problem: when I stop the codesys service everything works fine, as soon as I start codesys service it stops working.

I've gone through the forum and I've tried adding

[SysCom]
Linux.Devicefile=/dev/ttyUSB

to CODESYScontrol.cfg but this doesnt fix my problem.

So some questions...
1: Can someone explain why codesyscontrol.service would cause this problem?
2: What exactly does
[SysCom]
Linux.Devicefile=/dev/ttyUSB
do? I suspect it points codesys to the correct hardware address for serial communication?
3: In some forum posts I see
portnum := COM.SysCom.SYS_COMPORT1
added to the .cfg, what does this do?
4: Final question, how do I fix my problem?

Thank you in advance.

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