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Modbus Starting Page

A guide and index to Modbus resources in this Wiki

Python Code Samples

At present there is no complete "Modbus Library" since by itself it cannot do anything - thus one needs to define how one wants Modbus to integrate with a Python application before one can have a library. Here are Wiki pages which explain the basic concepts for creating Modbus requests under Python:

Leveraging the Modbus Bridge in the WAN IA / X4 / X8 products

Some Digi products include a powerful multi-master Modbus Bridge which freely converts between Modbus/TCP, Modbus/RTU and Modbus/ASCII. Thus your Modbus Python code can be quite simple, yet have full function. This page explains the integration:

External resources

What is Modbus? It is a 30 year old protocol which is best described as a "remote memory table access protocol". It literally allows a client/master to go to a server/slave and ask "return 16-bit words, starting at offset 23 and include 4 words". Modbus places no interpretation on that data; it assumes the client/master and server/slave AGREE as to the meaning. So 4 words of data might consist of:

  • one word with 16 status (on/off) bits
  • one word of unsigned data with only valid meaning from 0 to 10,000
  • two words as a 32-bit float, however Modbus doesn't even promise WHICH of the two words is the upper word and which is lower word

The Modbus specification is here:

Here is background info on Modbus:

Pages in Category Modbus

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