Need Help with RS485 Communication on Revolution Pi Connect SE

[Bhanu Kiran]

Hi all,

I'm a newcomer to Revolution Pi, currently utilizing the Revolution Pi Connect S with an RS485 terminal for my project. I'm trying to establish communication using the built-in RS485 terminal but am facing some issues. Modbus communication is working as expected with python code using Py Modbus master but has issue with built-in Modbus Master using PiCtory.

Here’s a breakdown of my current setup:

- Network Configuration: There is only one slave device on the RS485 network.
- Connection Details: I have connected only the data lines to the built-in RS485 terminal. The ground cable is not connected to the Revolution Pi's inbuilt RS485 terminal.
- Power Supply: Both the Power and 0V lines are directly connected from the power supply to the slave device, while only the Data cables (RS485A and RS485B) are linked to the Revolution Pi Connect SE.

1. Question about Termination Resistor: Does the Revolution Pi Connect SE come with a built-in pull-up resistor for the Modbus slave network, or do I need to add a termination resistor externally?

2. Successful Communication: I have successfully communicated with a slave device using a python code. The setup was controlled via a Complete Python program utilizing the py-modbus library, and communication performed as expected. You can find an attached picture showing this setup.

3. Issue with Built-in Modbus Master: After confirming the cabling was correct with the python code (where the communication is working), I attempted to use the built-in Modbus Master using Pictory. Unfortunately, I am unable to establish communication using this method.

Any insights or suggestions on how to resolve the communication issue with the built-in terminal would be greatly appreciated!

Thank you!