I cant read more than 5 modbus Holding register

General
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1

Hi! Im creating a Dashboard to show diferent values extracted from an equipment. I can read the just 5 modbus adress, but when I try to get 6 or more readings lost all the connections. How can I fix it?

2

Hi unfortunately nowhere near enough info I'm afraid.

What device is it? What address are you accessing? Can you link to a manual that lists the registers?

Lastly, can you clarify this ...

... What exactly happens?

3

Hi! Im Agree, I going to try to be clearest:

Device: Battery Energy Storage System-
Address: I can read any address, but just 5 as maximum, If I try to read 6 address so it disconnect some nodes.

In the first image Just reading 5 address (from 12295 to 12299) and all ok:

5 address
5 address695Ă—410 47.4 KB

In the second image trying to read 6 address (from 12295 to 12300) but I dont understand why it disconnect some nodes:

6 address
6 address718Ă—425 49.8 KB

Function Code: 3 read holding register
Poll rate: 2 seconds

best regards!!

4

I read 60 registers with no issue but use only one node. why do you have so many nodes ?

can you not put address 12295 and put 10 quantity ?

image

can you show the setting of the node like above ?

5

This is the least efficient and most problematic way of gathering data I'm afraid. This document has some good advice and practical info directly related to your requirement: Modernize your legacy industrial data. Part 2. • FlowFuse

6

Thanks, I Feel this is the best option. But Im concerning about use just one node in my scenarios , let me show you how the registers address are distributed:
image

In this case, is ok read in one node from 257 until 24643 address? it mean 24386 registers, I feel it is a lot, but Im not sure if it is any problem.

7

Thanks! I read it, it is too helpful to understand more about the modbus efficiency!

8

No, the maximum read count is 125 registers in one request.

9

Got it. So, it is a limitation for my case? is any way to get all the data? or should I look for something different to node-red?

10

The limitation is the modbus specification, not node-red. Other software will have exactly the same limitations. The are some exceptions like certain PLC's but typically, 125 is the protocol limitation

11

Your best bet is to read those ranges 1 at a time by connecting the modbus nodes in series instead of parallel.

12

Thanks, do you mean something similar like this?? How to create an Modbus-TCP alarm status dashboard - #20 by Steve-Mcl

13

In series, like that example, yes.

14

thanks it work for me. Is my first time in this forum and the experience was so good.