ModBus multipoll word swapping support

Posted almost 6 years ago by Josse Aertssen

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Josse Aertssen

Currently we use the multipoll node to allow flexible reading of multiple device types.

The queries are configured via flows and webui.

Current data types only have support for big endian and little endian, however in ModBus there is also a mode where the words are swapped, so the data should be interpreted as CDAB. (example for 32bit value)

Can this mode be added in the format list? Right now I worked around this with bit.ror operations but I'd like to properly support this mode in the flows.

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OPTION Support

OPTION Support posted over 5 years ago Admin

Hi Dean,

That is a good work around in case you have a format that the multipoll node doesn't support, which the extract node does.

Making one large request is indeed more efficient than multiple smaller ones.
That is why the multipoll node already combines smaller requests into one larger one (if possible) and splits the result automatically.

Best regards,


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Dean Laing posted over 5 years ago

What i did which works very nicely is use the single poll to poll 124 registers, then use the extract node to process the data. the extract node gives you six different combinations of ABCD. it is also best practice to make one large request instead of a bunch of single ones like with the multipoll

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