Control a Crouzet em4 automaton with Python

I have a Crouzet em4 automaton that controls a pump and I would like to control the automaton with a Python script in order to start and stop the pump. I’ve heard it was possible but I’m stuck right now.

The initial configuration of the automation has been done by someone else and he hasn’t left much specs on it. I have access to the configuration file of the automaton but it only gives me the architecture of the automation and I don’t have (or at least I can’t find) a way to link the blocs of the program with register to input data with python.

I tried to remotely control the automation with the Crouzet Soft (a working feature) to see with wireshark if I could have some data. Unfortunately, I only have ACK from TCP and TLS protocol messages. I hope the soft and the automaton speak with Modbus but I can’t find any way to validate or unvalidate this guess.

When I try to write or read information from coils or holding registers with pymodbus, I can see that the automation reacts to Modbus protocol, however, I don’t know how to write or read in the right registers.

All I know right now is that my pump is connected to the output O1 and that it’s a PWM output.

If you have some clues to help me solve my problem I would be glad.