In Modbus RTU, if master sends broadcast message to slaves, will slaves devices respond to the master with information?
In our current setup, modbus slave device is connected to PC application via USB. PC application detects the slave device and assigns it a modbus address.
In our new setup, there is a gateway board between PC application and slave devices. PC application will detect gateway board because it is directly connected to PC application via USB. But it won't detect slave devices because they are not directly connected the PC application.
Somehow PC application has to be informed as to which slave devices are on the modbus network so it can assign addresses to slave devices.
I'm thinking about using broadcast adress 0 to find out the identification of slave devices. Master Gateway will send broadcast messages to slaves. Will they respond to gateway?
In broadcast mode, the master can send a request to all slaves. No response is returned to broadcast requests sent by the master. The broadcast requests are necessarily writing commands. All devices MUST accept the broadcast for writing function. The address 0 is reserved to identify a broadcast exchange.
What do you think would happen if all slave devices replied to a broadcast request over the same line at the same time?
I know there will be massive bus contention if all slave devices replied to a broadcast request over the same line at the same time. I was going to think about a solution to this bus contention issue but I don't need to do that because now I know there is no response to broadcast.
Somehow I need to inform PC application what slaves are on the modbus RTU network so PC application can assign modbus address to slave devices.
Any ideas?
Thank you for answering the original question. I got answer to my follow-up question.