Hi, I have a sensor that outputs three variables, and I need to write those three variables to a server using Modbus TCP/IP. I would do this with the ModbusMaster() instruction, but where would I configure the server's IP address? TCPOpen?
Could someone help me?
Use TCPOpen() to open the connection. Use the socket number returned by TCPOpen for the comport in ModbusMaster().
Writing data over Modbus TCP/IP can feel confusing at first, but the idea is simple: the server waits for specific register writes, and the client pushes values to those addresses. The main challenge is making sure both sides agree on register mapping and data format. If the mapping is off, the server receives the request but nothing changes. Once the addresses and function codes match, the communication becomes steady and predictable. It’s one of those setups where a small configuration detail can make the whole system finally click.
When you're using ModbusMaster to send your sensor data to a server, you'll need to tell your program where that server is - specifically, its IP address. Usually, this is done when you open the connection, which is done with the TCPOpen() function.
Think of TCPOpen() as dialing up the server. When you call it, you give it the server's IP address and the port number (which is often 502 for Modbus). Once the connection is open, you can send your three variables using Modbus commands.