Performance of Modbus RTU server

[MinzaGayas]

I am developing a Modbus server using pymodbus v2.5.3 synchronous server and RTU framer. The client is sending requests @600ms. I have set the serial socket with timeout of 1s because below this, framer does not send proper responses. Can the framer work at below 1s limit because it loses half of the requests sent by client?

[janiversen]

The framer does not have demands on timing, apart from the 3.5character wait between messages. The framer depends on the driver to do the read timeout.

[janiversen]

Timeout should normally be:
0 < timeout < time to send 3.5char

[MinzaGayas]

Does it also depend on the number of bytes serial socket has to read? say 256bytes in this case

[janiversen]

it is timeout, not a time to read.

[MinzaGayas]

I am trying to set this timeout of serial-Serial socket in _connect function of server file sync.py
self.socket = serial.Serial(port=self.device, timeout=self.timeout, bytesize=self.bytesize, stopbits=self.stopbits, baudrate=self.baudrate, parity=self.parity)
I have not made any changes to framer timings for 3.5char wait.
With timeout set at 3ms, framer still gives these errors. Also, Modbus sniffer does not show the responses with a proper start if timeout is set less than 1s.

[MinzaGayas]

Hi @janiversen,
After doing more analysis, I suppressed any responses from the server and just tried to receive client requests. Regardless of timeout value set, the framer either shows frame not ready or frame check failed for half of the requests being received.
what could be the possible reason behind this? It does not seem to depend on serial read timeout at all. Is the client too fast for it?

[janiversen]

How is your development progressing ?

[MinzaGayas]

It is still stuck with RTU framer not responding to below 1s request rate :(

[janiversen]

have you upgraded to our current version, a lot of changes went into version 3.0 and more in the other versions.

I have no problem with sending frames very fast.