Problem with Node-red- Modbus / S7 node

General
1

Hi Everyone,

  1. I am presently working on Siemens S7-1500 PLC. I configured the PLC as modbus client. Now, I am trying to read the holding registers using Modbus read. But unfortunately, I am unable to establish the connection, The status on the node shows "Initialize" changes to "Error FSM not ready to read at state INIT" and then reconnecting. I have no clue how to solve this issue please help.

  2. I have also tried using node S7 node to connect the PLC but as soon as I enter the IP address and deploy it the status on the node changes to disconnect.

Please give your valuable suggestions.

Regards,
Somavaram

modbus_error
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2

I suggest you start by googling for
Error FSM not ready to read at state INIT
That shows a number of hits that may be relevant to your problem.

3

hello :smiley:

I'm using s7 node and work really nice.

in the PLC you have "Put / Get ..." active ?

Is "DB" configured without optimization? the plc port must also be configured on the S7 node

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but this all depends on the firmware version of your CPU, in the most extreme cases that happened to me, I added a PC in the network

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Node-Red side:

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configure your plc ip and rack , slot.....

how to read ?

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DB number, DB offset

2 Likes
4

Hi @Cristiano,

Thanks a lot for the pics. I am new to TIA Portal siemens. I configured the the PLC but I have not configured the Node-red PC. What does the PC Station do ? What PC systems should I use for the desktop? How do I configure it?

I am currenty using CPU 1512SP F-1 firmvare V2.1

Regards,
Somavaram

5

Hello

adding the station is not mandatory, but I used it in strange cases with the v1.x firmware. With firmware v2 I think it works without the station, but I'll leave the print below

1 step:

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2step: add network board

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3step: drag n drop connection
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Are you using the cpu simulator? or are you testing with a physical cpu?

6

Hi @Cristiano,

Thank you again for the pics. I am testing it on a physical device.
Didn't work after using a pc station as well.

Regards,
Somavaram

7

Hi @somavaram
have you tried to ping your PLC from the machine where you are running Node-RED? Does it ping?
If yes what happens if you only configure the IP address and rack and let the DB variables table empty?

8

You are a lifesaver