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A PLC communication library for Python

Project Description

pycomm is a package that includes a collection of modules used to communicate with PLCs. At the moment the first module in the package is ab_comm.


The library is currently test on Python 2.6, 2.7.


The package can be installed from


git clone
cd pycomm
sudo python install


pip install pycomm


ab_comm is a module that contains a set of classes used to interface Rockwell PLCs using Ethernet/IP protocol. The “clx” class can be used to communicate with Compactlogix, Controllogix PLCs The “slc” can be used to communicate with Micrologix or SLC PLCs

I tried to followCIP specifications volume 1 and 2 as well as Rockwell Automation Publication 1756-PM020-EN-P - November 2012 .

See the following snippet for communication with a Controllogix PLC:

from pycomm.ab_comm.clx import Driver as ClxDriver
import logging

if __name__ == '__main__':
        format="%(levelname)-10s %(asctime)s %(message)s",
    c = ClxDriver()


        print(c.read_tag(['parts', 'ControlWord', 'Counts']))

        print(c.write_tag('Counts', -26, 'INT'))
        print(c.write_tag(('Counts', 26, 'INT')))
        print(c.write_tag([('Counts', 26, 'INT')]))
        print(c.write_tag([('Counts', -26, 'INT'), ('ControlWord', -30, 'DINT'), ('parts', 31, 'DINT')]))

        # To read an array
        r_array = c.read_array("TotalCount", 1750)
        for tag in r_array:
            print (tag)

        # reset tha array to all 0
        w_array = []
        for i in xrange(1750):
        c.write_array("TotalCount", "SINT", w_array)


See the following snippet for communication with a Micrologix PLC:

from pycomm.ab_comm.slc import Driver as SlcDriver
import logging

if __name__ == '__main__':
        format="%(levelname)-10s %(asctime)s %(message)s",
    c = SlcDriver()

        print c.read_tag('S:1/5')
        print c.read_tag('S:60', 2)

        print c.write_tag('N7:0', [-30, 32767, -32767])
        print c.write_tag('N7:0', 21)
        print c.read_tag('N7:0', 10)

        print c.write_tag('F8:0', [3.1, 4.95, -32.89])
        print c.write_tag('F8:0', 21)
        print c.read_tag('F8:0', 3)

        print c.write_tag('B3:100', [23, -1, 4, 9])
        print c.write_tag('B3:100', 21)
        print c.read_tag('B3:100', 4)

        print c.write_tag('T4:3.PRE', 431)
        print c.read_tag('T4:3.PRE')
        print c.write_tag('C5:0.PRE', 501)
        print c.read_tag('C5:0.PRE')
        print c.write_tag('T4:3.ACC', 432)
        print c.read_tag('T4:3.ACC')
        print c.write_tag('C5:0.ACC', 502)
        print c.read_tag('C5:0.ACC')

        c.write_tag('T4:2.EN', 0)
        c.write_tag('T4:2.TT', 0)
        c.write_tag('T4:2.DN', 0)
        print c.read_tag('T4:2.EN', 1)
        print c.read_tag('T4:2.TT', 1)
        print c.read_tag('T4:2.DN',)

        c.write_tag('C5:0.CU', 1)
        c.write_tag('C5:0.CD', 0)
        c.write_tag('C5:0.DN', 1)
        c.write_tag('C5:0.OV', 0)
        c.write_tag('C5:0.UN', 1)
        c.write_tag('C5:0.UA', 0)
        print c.read_tag('C5:0.CU')
        print c.read_tag('C5:0.CD')
        print c.read_tag('C5:0.DN')
        print c.read_tag('C5:0.OV')
        print c.read_tag('C5:0.UN')
        print c.read_tag('C5:0.UA')

        c.write_tag('B3:100', 1)
        print c.read_tag('B3:100')

        c.write_tag('B3/3955', 1)
        print c.read_tag('B3/3955')

        c.write_tag('N7:0/2', 1)
        print c.read_tag('N7:0/2')

        print c.write_tag('O:0.0/4', 1)
        print c.read_tag('O:0.0/4')


The Future

This package is under development. The modules _ab_comm.clx_ and _ab_comm.slc_ are completed at moment but other drivers will be added in the future.


Thanks to patrickjmcd for the help with the Direct Connections and thanks in advance to anyone for feedback and suggestions.


pycomm is distributed under the MIT License

Release History

This version
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