# Node Red - Modbus Custom FC

**URL:** <https://discourse.nodered.org/t/node-red-modbus-custom-fc/94438>\
**Category:** General\
**Created:** [7 January 2025 20:35 UTC](https://discourse.nodered.org/t/node-red-modbus-custom-fc/94438 "2025-01-07T20:35:05Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [7 January 2025 21:37 UTC](https://discourse.nodered.org/t/node-red-modbus-custom-fc/94438/2 "2025-01-07T21:37:50Z")

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I don't think any of the modbus nodes are developed to support custom function codes.

I have previously done a POC, custom parsing that could be modified to use the serial nodes and support any FC - it is after all just simple ASCII codes and checksums.

> [@How to create an Modbus-TCP alarm status dashboard](https://discourse.nodered.org/t/how-to-create-an-modbus-tcp-alarm-status-dashboard/43041/14):
>
> Slight update: Added header checks - works quite nicely reading 350 registers... [{"id":"f77e01bf.42f16","type":"inject","z":"5e6c8b.7f38b374","name":"FC4: Read 50 from address 100","props":[{"p":"topic","vt":"str"},{"p":"sid","v":"1","vt":"num"},{"p":"pid","v":"0","vt":"num"},{"p":"len","v":"6","vt":"num"},{"p":"uid","v":"1","vt":"num"},{"p":"fc","v":"4","vt":"num"},{"p":"address","v":"100","vt":"num"},{"p":"registerCount","v":"50","vt":"num"}],"repeat":"","crontab":"","once":false,"…

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