Modbus Failure On State sending Get More About It By Logging

I am using a USB to RS485 converter (Waveshare) on my Raspberry Pi 4 to query two power meter (SDM630) via Modbus RTU using the Modbus-Flex-Getter. Everything works fine and stable without any errors over days as long as I don't touch the Flow (and especially the Flex-Getter-Node).

However if I am changing anything in the Flex-Getter-Node or in the Flow which sometimes causes the Flex-Getter-Node to do a reconnect, I get the following error messages:

The only thing I can do to get the Modbus communication working again is to restart Node-Red. It's not a big deal as it works perfectly fine if I don't touch the Flow, it's a somewhat annoying behavior regardless and I don't know where to start to debug this.

Here are my settings:


Raspberry Pi 4
Debian GNU/Linux 11 (bullseye)
Linux: 6.1.21-v8+

Node-Red: 3.1.3
node-red-contrib-modbus: 5.27.2
NodeJs: v20.11.0

Nodejs version 20 is not listed as tested / compatible with the Modbus nodes and some issue was reported on Github page (source)


try downgrading to Node version 18

If you want to further test before downgrading nodejs .. try to stop Node-red and run it with command
DEBUG=contribModbus*,modbus-serial node-red -v

this will give you a more detailed log in the terminal, of each of the Modbus nodes actions (source)

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Downgrading to NodeJS 18 did the trick! Now the Flex-Getter-Node is reconnecting properly without having to restart Node-Red first! Thanks a lot! :slight_smile:

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