I have 7 Modbus room thermostats, 1 relay pack and 1 electricity meter on the bus currently. All works good until one device in the bus loses power. Each of the other devices go to "reconnect" state and they are not able to get back up until the one device is powered on again. I am not very familia…

There is a certain amount of guesswork in the following, but I am sure it is close to describing what is happening. The first thing to remember is that all of the comms is happening down one pair of wires and that only one device can be polled at a time. All the comms passes through the one modbus…

[image] Weller1: I am using Moxa usb to modbus adapter Do you mean usb to serial? Or is it a specialist modbus device? Did you read the first sentence of the help text for the modbus read node? " If you have more than 10 nodes on one communication configuration, use the Modbus-Flex-Getter …

Ah sorry. Yes I mean USB to Serial converter. UPORT 1130 is the model if I remember correctly. I did some testing today and found out that by using the older package called node-red-contrib-serial-modbus, the bus works correctly. By using that package I was able to keep polling other devices while…

Could you export that flow here please? See this post for details of how to do that if you don't know - How to share code or flow json

[image] Weller1: Any ideas on what should I check ? Have you asked the developer on the Git Hub site? If anyone knows, it would be the one(s) who made it.

I suspect I know what the problem is, but I need to see the flow.

How is your termination on the Bus setup ? As you know RS485 is setup as a Serial connection topology where a single pair of cables goes from each device to the next - some devices have an IN and an OUT port - others you just wire the cables between them The most important thing is that to operate…

Here is the code I been testing with now [{"id":"bdc7638d.9337f","type":"debug","z":"54bc74df.bb994c","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":1390,"y":400,"wires":[]},{"id":"87186745.9fbb98","type":"modbus-f…

Thanks for the help! This seemed to be my problem. I changed the Timeout (ms) to 100ms and untick the Reconnect on timeout. Now it seems to be able to keep the bus on even tho one device dies. And I think I also now understood what went wrong there. I have one more question regarding this. What sh…

[image] Weller1: The answers will start to stutter and messages come in very randomly. Why will they?

[image] Weller1: I have one more question regarding this. What should be the best/proper way to poll the devices? Clearly if I poll each of my 9 devices with the flex-getter like in the picture (with 1 second inject interval). The answers will start to stutter and messages come in very randomly.…

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Modbus Serial - Whole bus disconnects when one device drops

General

Steve-Mcl 21 July 2021 07:13 16

Your best bet is to wire in series.

Read Registers From Modbus Not in Sequence

I need to perform an arithmetic operation between 2 variables of the same modbus device

read 2 spaces with node-red-contrib-modbustcp

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Modbus Serial - Whole bus disconnects when one device drops

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