Is it possible to send a value to multiple MODBUS devices at a time?

If I have 5 MODBUS devices with devices IDs 1,2,3,4 and 5. Is it possible to send a value to the same register of all 5 devices together?

Not in a single device transaction. The modbus protocol doesn’t have any way to address multiple devices in a single operation. The closest you can get is to pack all five writes into a single system.opc.writeValues() call.

In theory you can write to address 0. That’s the broadcast address. You’ll have to make sure the slaves support that. They will not respond, so your write will get a timeout even if it works.

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Whenever I am sending something to 0, nothing happens.