No. It would require his firmware. What I’m saying is that after issuing a command, I can verify that the command was received on the next check of the registers.
Are you talking about the connection between the two in general? I’d need to check with him about how that’s initiated, but modbus is a well defined and understood data communications protocol going back to the 1970s, which is why he’s suggesting it. Assuming the libraries referenced in my first post work well with Xojo, the understanding is I don’t really need to think too much about the underlying transport issues, just what/when to send and retrieve data.
More Specifically, I’m referring to this post by @Dennis_Hoskins