MODBUS RTU discovery.

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Hi,
I'm building a java modbus data acquisition system (using MODBUS4J), I've successfully communicated with the modbus device using its slave id, address, datatype.

But is there a way to just detect slaves, by just addressing slaves from 0-255 without specific register or coil addresses? So, that slaves with matching slaveId's respond.

Modbus does not provide a built-in way of detecting slaves. So to do what you want to do would need to be a hack or workaround...Such as polling each slave, if there is a response from that slaveId even if it is an error code such as "illegal address", then there is probably a slave of that ID ??