Modbus-Tk RTU Server

[Brad Natelborg]

Hi,

I'm trying to create an RTU server using Modbus-TK.  For testing purposes, I want to imitate several real MODBUS devices on a raspberry Pi using Modbus-TK.  I want to connect the raspberry Pi to an existing MODBUS network, which will have multiple MODBUS slaves on it.

I am able to get a server running using the example, and I was even able to get a couple of hooks set up, but it appears that the server fails when it receives a slave ID that is not one of it's own?  I'm hooking up the raspberry Pi to a MODBUS network with multiple other devices on it, so there is quite a bit of traffic going across the network for many different slave IDs.  I have the Modbus-tk server set up with Slave ID #10, but it throws an error for Slave ID #1 (which is for a different device).

You can see the error I'm getting below:

sudo python3 server.py                                                                     
RtuServer /dev/ttyUSB0 is opened                                                                                       
running...                                                                                                             
enter 'quit' for closing the server                                                                                 
After Read bytearray(b'\x01\x03\x00\x00\x00\x02\xc4\x0b')handle request failed: Slave 1 doesn't exist                   
Before Write b'\x83\x04'
After Write b'\x83\x04'
After Read bytearray(b'\x01\x03\x04\x00\xe4\x01F:f')handle request failed: Slave 1 doesn't exist

How can I set up an RTU MODBUS server to only respond to messages that are for the slave IDs that it owns?

Thanks! 

[Brad Natelborg]

Answered my own question.

You can set the `error_on_missing_slave` flag to `False`.  

server = modbus_rtu.RtuServer(serial.Serial(port=PORT,

baudrate=BAUDRATE,

bytesize=BYTESIZE,

parity=PARITY,

stopbits=STOPBITS),

error_on_missing_slave=False)