ModBus function code 23

We have a added a new piece of equipment and unfortunately this device only support ModBus function 23 for Writing multiple registers. The generel Modbus nodes only support code 16 for writing multiple registers, and does not support code 23. I have not been able to find anything supporting code 23 in the available node-red pallets. Does one of you know if there is a node that support code 23, or if it is possible to program this in a funtion node?

It is certainly possible to write this in a function node.

Here is a simple demo i did using node-red core nodes + buffer-parser.

It doesnt do writes or support fn 23 but it is certainly not impossible (or that difficult) to do.

You would have to read the spec for FN23 to know how to format the bytes. Alternatively, you could wireshark a working implementation & work it out easily enough.


Hi Steve, Thanks for the example. I downloaded the example and tried to understand how it is working but I am not able to see what I would need to write in a function to write to a holding register. If I would like to write a specific value to register 200, what would I need to have in the function node.

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