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pythonraspberry-pigpioplc

Raspberry Pi to AB controllogix: how to trigger output in GPIO based on continuosly reading plc tag value


I've discovered pylogix on GitHub and have been playing around with reading/writing tags on an AB L71 CPU. I am successful at the read/write part, but what I want to do is trigger a GPIO pin output based on plc value being larger than 0.

I can't seem to figure out what I need to do to get the constantly updated value into the output function.

import threading
from pylogix.eip import PLC
from gpiozero import LED
from time import sleep

comm = PLC()
comm.IPAddress = '10.201.191.177'

def readdata():
    threading.Timer(1.0, readdata).start()
    x = comm.Read('parts')
    print (x)
readdata()

if x > 0:
relay = LED(2)

Solution

  • It's nice to see I'm not the only one interested in PLCs on this forum. I might recommend this for you:

    Edit: I read the docs for your module. try this new code below docs can be found https://gpiozero.readthedocs.io/en/stable/

    import threading # I don't think this is necessity for your application
    import time
    from pylogix.eip import PLC
    from gpiozero import LED
    from time import sleep
    
    with PLC() as comm #small edit here to control the closing of sockets upon exit
        comm.IPAddress = '10.201.191.177'
        running=True
        relay = LED(2) #I believe the previous version of your code was constantly overwriting your 'relay' variable with a new instance of class LED
        while running==True:
            x=comm.read('parts')
            if x > 0:
                relay.on()
            else: relay.off()
        time.sleep(.5)
    #this will run forever updating your LED every 500ms, I would recommend writing code to exit this loop