LOGO! 8 (FS4) as modbus server

Hi all,

I am trying to read inputs of the LOGO!8 with node red (using IOT 2020). I I'm using modbus TCP as a communication protocol.

I made a successful communication, I do get some data, but not what I want.

The mapping of the LOGO! is in attachement, witch function codes correspond to these address types, because when try function code 2 (input status) I find the values "false", but when I activate an input (with a button), I get nothing changed.

See attached table to find the right Modbus registers. If the beginning address is 0, then reduce numbers by 1.

Regards, Scorp

Hi scorp, 

According to your table , is it okay to fill the I/O table like this ? (see attachement)

As ixo65 has written it would be better to use the S7 protocol instead of Modbus with iot2020/2040.

You can use Modbus, if you absolutely want, but then don't create a vm mapping.  Open a new diagram, a network project is not needed. Then go to the menu Tools -> Ethernet connections and create a Modbus server, allow all connections or only from one ip address, that's all.If you have several Modbus connections, then you can change the port 502 to 503, 504... as you need.

Regards, Scorp

ixo65, I got your idea.

I have an iot2020, I went for the modbus method because I could not install node-red-contrib-s7.

I tried several times without a result.

Ok Scorp,

I did what you said to me, now trying to pull the digital inputs. it's function code 02 in node red isn't it ?

perhaps the unit id is missing, but how to know it from LOGO Software ?

I don't know, how to setup iot2020 in node-red. If have not used it until now. Try 0 and 255 for the unit id and check this out. If both have no function, then ask in the IOT2000 forum.

You also can check the Logo itself with a PC Modbus client to ensure this part of the communication. You will find several Modbus clients in the internet without costs.

Regard, Scorp

P.S. Try also to read an other element, e.g. M1. For this use a pulse generator and connect the output to M1.