I have a PC setup as a modbus master. I have ONE modbus slave. I'm using modbus RTU over RS232. All works just fine.
I now want to add a second slave.
I read the way to do this is to use RS485 - i.e. implement a single to multipoint "network".
Having read up on RS485 it seems it's "thing" is it allows comms over longer distances than RS232. However, my TWO slaves and the master are physically within a few feet of each other so I had thought of implementing RS485 "in a box" i.e. 3 RS232 ports connected via a "foot long" RS485 but then thought - do I need to do this? - is this overkill? Can I not just connect the two RS232 slaves and the RS232 master "in parallel". There shouldn't be "bus" contention problems at the protocol level because modbus should handle this. BUT - can you do this at the "electrical" level?
So I guess what I'm asking is can you do this:
master(com1)(tx) -> RS232(rx)(slave1) -> RS232(rx)(slave2)
master(com1)(rx) <- RS232(tx)(slave1) <- RS232(tx)(slave2)
Thanks
I now want to add a second slave.
I read the way to do this is to use RS485 - i.e. implement a single to multipoint "network".
Having read up on RS485 it seems it's "thing" is it allows comms over longer distances than RS232. However, my TWO slaves and the master are physically within a few feet of each other so I had thought of implementing RS485 "in a box" i.e. 3 RS232 ports connected via a "foot long" RS485 but then thought - do I need to do this? - is this overkill? Can I not just connect the two RS232 slaves and the RS232 master "in parallel". There shouldn't be "bus" contention problems at the protocol level because modbus should handle this. BUT - can you do this at the "electrical" level?
So I guess what I'm asking is can you do this:
master(com1)(tx) -> RS232(rx)(slave1) -> RS232(rx)(slave2)
master(com1)(rx) <- RS232(tx)(slave1) <- RS232(tx)(slave2)
Thanks