Setting the Modbus Slave ID

Submitted by hanky on Wed, 01/27/2010 - 22:28
in

G'day,
i think an option to set the slae ID in the tag data would be useful. Sometimes you may have a Modbus TCP to Modbus RTU gateway with multiple small PLCs with different slave ID's on the RTU network. Being able to specify which slave ID a tag comes from could be quite useful.

Cheers

‹ Decimal Points in integers Modbus word-swapped tags ›

ScadaMobile currently

Submitted by Joan on Thu, 01/28/2010 - 09:46.

ScadaMobile currently defaults to Unit '1' as in most cases this is simply ignored by Modbus/TCP devices. But you are right the 'Unit Identifier' is typically used to communicate to serial line Modbus slaves through a Ethernet gateway. This ID clearly refers to or identifies a PLC but I think it should be still implemented in ScadaMobile at a tag level (not at a source level as it could seem), because the IP address where commands will have to be sent will be unique anyway. Am I right?

Thanks,

Joan
SweetWilliam, S.L.

Yes, i think it would be good

Submitted by hanky on Mon, 02/01/2010 - 02:05.

Yes, i think it would be good to be able to set it at a tag level. Usually the IP address is unique, however there are often lots of small controllers on a single RTU network which then feeds to a single Eth/Modbus gateway, so having it set for all may not be ideal. But as a first step, yes, if you could set the slave ID for a group of tags(or piece of 'equipment') that would be great.

Cheers