Modbus RTU problem reading address

Hi everyone,

I am using a IoT2050 in order to get data from a temperature controller (the attached document contains the controller's manual). The problem comes when I try to read the registers. The error I get is: "Error: Data length error, expected 7 got 1".
The wiring is correct as IoT2050 can recognize the controller:

I've use this nodes before without this problem and I don't know what can cause this error.

Any help will be welcome!! Thank you in advance

Here is some information about software version:
-Node.js: v12.22.5
-Node red: v2.0.6
-node-red-contrib-modbus: v5.14.1
-server configuration:
-node configuration:

Eurotherm-3216-3208-3204-User-Manual-Issue13.pdf (5.4 MB)

Hello .. by reading some similar issues on the Modbus node's Github page some people suggested trying


I've try this and now the meesage is: "Error: Timed out". Also Node red seems to not be ok with this...

have you confirmed that the Modbus node's settings for address, baud rate and parity are set the same as with your device's settings (page 90 in the manual) ..

For the node, you need to switch to Serial Expert to see all options

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Sorry for the delay.

Yes I've checked all the options. During these days I've doing several test with the computer and other software to ensure that the controller is working properly. The results have been satisfactory, so the problem is with IoT2050 or Node-red

I have tested the Node-red in a different device updating node-red to the last version available (v3.0.2). I've also updated the node-red-contrib-modbus (v5.23.1). Everything works properly so I suppose that the problem is in the IoT2050 periphericals.

Thank you for your help

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Im glad you managed to get it working in a different device ..
A while back i remember sharing a video i found on the net that describes how they updated the IoT2050 to the latest versions for Node-red and Node-js .. personally im not familiar with the device but here is the post in case you want to ask the person that has it if everything is running smoothly.
Also you can try asking on the Siemens if they have any official update procedure.

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