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Control Crevis Modbus I/O Adapters using Python

Python module that lets you control discrete I/O pins on Modbus adapters from Crevis. E.g. the NA9189.

The module uses the following, possibly very idiosyncratic, terminology:

Term Meaning
Adapter Represents an entire I/O device.
Module Each adapter has 0 or more modules connected to it.
Slot Each module is referenced by its slot number, i.e. distance from the adapter.
Pin The pin number on a module, a slot:pin tuple identifies a specific pin.

To use it:

import crevisio

# Connect to the adapter
io = crevisio.adapter('198.18.122.10')

# Show some info about the adapter
print repr(io)

# Enable module 0, output pin 4
io[0][4] = True

cio

A commandline interface to crevisio.

In a typical setup, you often contact the same I/O, and have fixed equipment connected to the I/O pins. For that reason, cio can read the default address from a configuration file, avoiding the need to specify it at every invocation. The configuration file can also be used to reference individual pins using aliases.

A simple example may look like this:

address: 192.168.0.100

aliases:
  - name: coffee-maker
    slot: 0
    pin:  1
  - name: nuke
    slot: 0
    pin:  4
  - name: door-bell
    slot: 0
    pin:  5

If you install the argcomplete package, cio will be able to autocomplete pin aliases from your configuration file.

cio will load the first file in any of the following paths:

  • ~/.cio.yaml
  • ~/.config/cio.yaml
  • /etc/cio.yaml

That means that if your system administrator has setup cio already, you do not have to do anything. But if you would like to use a different address, or different aliases, you can override the system default settings.

See cio --help for more information on command usage.