Problem with Node-red- Modbus / S7 node

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.


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.

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

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

Node-Red side:

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

how to read ?

DB number, DB offset


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



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:

2step: add network board

3step: drag n drop connection

Are you using the cpu simulator? or are you testing with a physical cpu?

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.


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?

You are a lifesaver