Node-Red Modbus write node's not working

In my house i have main automation (lights, heating, Hot water) done using Unipi PLC controller and Home Assistant on Raspberry Pi4 for additional task like camera, tracking and some more other things.
Both controllers are integrated using modbus , on home assistant i have Node red addon to read data from Unipi1.1. I have 16 read nodes for coils, 2 read nodes for holding registers (for temperature) and 2 nodes for writing data to coils controlling heating and hot water. For several months it was everything ok exept sometimes after update core or node red addon i experience some problems with write nodes(not working). Usually restarting helps so overall it was ok. Last week i add 7 more read nodes, also i done core and node red updates, form then all read nodes work perfect but write nodes sometimes work but very slow and then not working at all.
For few days im trying to solve the promlem but no luck…
Any help will be helpful.
Thanks in advance.

I don’t use mod bus but have seen quite a few post recently because of changes to the platform. Have you tried to write from HA? You can go to dev tools under services. try to write to one of your devices to see if this isn’t from changes made to the core.

Hello Mike.
Thanks for reply. I try to configure modbus device using configuration.yaml file and looks like you right, in my opinion something its wrong with modbus libraries on HA. I spend a lot of time to learn modbus and i dont believe my settings are wrong.
BTW are you trying to say Node red addon using modbus libraries from HA not Node red one’s?

I don’t know how much is handled by HA. On a supervised pi HA is the OS so who knows. There are 2 ways of looking at it. If it does use HA’s library’s then you’ll need to check the forum for what changed.

If it is independent, then you have 2 clients that are having trouble communicating to you modbus controller. So maybe it’s in the connection.

Modbus is a pretty raw protocol, I’d guess that you could sniff the packets being sent with wireshark. Then be able to look at the message structure to see what’s being sent.

Another option would be to search nodered’s forum for recent modbus problems.


Yes, i create exactly the same topic on Node-RED forum as well

In the end i think problem was too many read node’s in configuration, it’s not recommended to use more then 10, even if it’s working cause problems with forcing coils.
The best solution was reading coils and holding registers using Buffer-Parser node (as on pictures).
Thank You for help.

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