MODBUS - Beginner Level Information to build an MODBUS Gateway

[Satya Prasad]

I am new to MODBUS and Fieldbus protocols. However I am trying to learn it. My tasks currently is to build a MODBUS application that receives MODBUS messages via Master then change the register / coil number and send it to another slave. Then wait for message response from the slave and send it back to Master.

I am using modbus-tk module but not able to understand how to create an synchronous client that waits for a messages and identifies message type. Then extract the register / coil number and set in as request to other slave and wait response from its end. Then create the response to be sand to MODBUS server.

Is there an example that I can refer using modbus-tk library?

How do we map the request and response accordingly in the app?

How can I timeout in case no response from slave?

Please provide some details to start with to build such an application?

The objective to understand both Modbus master / client implementation.