Modbus RTU telegram

[Valdievil]

Hallo everyone,

I need to send the following telegram to activate the remote control functionality of a device over Modbus RTU

00 05 01 92 FF 00 2D FA

The data sheet of the device says that 00 should be the head of the telegram as it is used dsitinguish between SCPI commands of ModBus

05 is the function code (Write single coil)

01 92 The address of the register

FF 00 the value to write in the register

2D FA is the checksum

Attached is a pic of the vi I made, but I keep getting the error −389112 regardless of whatever I try. Even reading registers throws the same error. Also I don't seem to completely undestand how to relate the telegram to the labview programming, specially the head 00 and the checksum 2DFA.

Thanks for help!

Regards

[K C]

Hi, 

In the picture I see a '1' as an input of the Unit ID. I assume that this is the slave address.

However in the data the first byte is a '00' That first byte is the slave address.

If you send data with the slave address at '00' it is handled as a broadcast to every slave with no response from a slave.

If you want to address slave 1 the data should be: 01 05 0192 FF00 2C2B

(The checksum of your data string (2DFA) is correct)

Kees