I am trying to determining if there is a way to write data directly to a manufactured HMI that is capable of Modbus TCP/IP communications. I want to display values that are stored in an SQL database for example, on the HMI screen. There would be no PLC in this system. Is this possible?
If it works as a modbus slave that you can send modbus data to that gets displayed then it should be possible using one of the modbus nodes. I am not certain from your description whether it does function like that though.
Sorry, is believe it is a slave in that regard? I am able to get modbus register data displayed to this HMI from other devices on the same network...for example I have a small Advantech unit counting pulses, and I can display the total number of pulses collected to this HMI screen. (Register 40002 for example) That device is set up with an static IP address and using port 502.
I think that means that the HMI is a modbus master, and asks the other devices for data which gets displayed. Is that right? If so then you would need a modbus slave node in node red. I am not aware of a modbus slave node.
I believe you are completely correct, and since there is not a slave node, I may be out of luck.