pcom 0.5

A basic PCOM implementation in Python

PCOM

A very basic Unitronics PCOM protocol implementation for Python 3.

How to use

from pcom import commands
from pcom.plc import EthernetPlc

with EthernetPlc(address=('192.168.5.43', 1616)) as plc:
    # Read realtime clock
    c = commands.ReadRtc()
    res = plc.send(c)
    print(res)

    # Set realtime clock
    c = commands.SetRtc(value=datetime.now())
    plc.send(c)

    # Set MB 300 through 304
    values = [True, False, True, True, False]
    c = commands.SetBits(code=commands.SetBits.MEMORY, address=300, values=values)
    plc.send(c)

See the commands Python package for available commands.

Datatable commands are in the commands.datatables package. To work with a datatable, its structure has to be defined. Here's an example:

from pcom import commands
from pcom.plc import EthernetPlc


with EthernetPlc(address=('192.168.5.47', 1616)) as plc:
    table_structure = commands.datatables.DatatableStructure("My table", offset=19000, rows=2, columns=[
        commands.datatables.Int(),
        commands.datatables.Int(2),
        commands.datatables.Int(),
        commands.datatables.Int(),
        commands.datatables.Long(),
    ])
    c = commands.datatables.ReadDatatable(structure=table_structure, row_count=2)
    res = plc.send(c)
    print('My table', res)

Writing to a datatable is very much alike:

from pcom import commands
from pcom.plc import EthernetPlc


with EthernetPlc(address=('192.168.5.47', 1616)) as plc:
    table_structure = commands.datatables.DatatableStructure("My table", offset=19000, rows=2, columns=[
        commands.datatables.Int(2),
        commands.datatables.Int(),
        commands.datatables.String(5),
        commands.datatables.Int(),
        commands.datatables.Int(),
        commands.datatables.Long(),
    ])

    rows = [
        [[11, 12], [13], "hello", [14], [15], [-673542]],
        [[11, 14], [15], "bye  ", [16], [17], [655666]],
    ]
    c = commands.datatables.WriteDatatable(structure=table_structure, data=rows)
    try:
        plc.send(c)
    except datatables.WriteDatatableError as ex:
        print(ex)

Known limitations

• General:
  • Serial communication is not implemented yet.
• Datatables:
  • "Part of project" columns are not supported.
  • Reading a datatable structure is not supported.