| Re: [volttron-dev] Custom Controller Agent Causes Modbus Read Error |
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Background:
I am using Volttron 8.1.3 on a Raspberry Pi to coordinate the operation / testing of 2 devices over Modbus:
- An energy storage system with a BMS that Volttron’s platform.driver communicates with over modbus
- An inverter that also communicates with Volttron’s platform.driver via modbus
Using the Listener Agent I can see that the platform.driver is reading all of my modbus points perfectly every 5 seconds (see the attached volttron_Without_Controller.log).
I have a simple custom agent, enervenue_ctrlagent (see the “agent.txt” file, changed from “agent.py” for attaching), that is subscribed to the "devices/STAC/EnervenueBMS" topic and runs a simple read from the battery, decide what to do, and write to the inverter loop every 5 seconds when new "devices/STAC/EnervenueBMS" data comes in. The writing is just to a single “Output Power Command” register on the inverter.
The Problem:
When enervenue_ctrlagent is installed and started, modbus reads of the inverter begin to fail. The controller’s attempts to write power setpoints are successful, but I start to receive this modbus_tk error (see the attached volttron_With_Controller.log):
Expected Behavior:
I was expecting that my controller agent should be able to run in tandem with the platform agent with no conflicts between reading and writing, but something funny is happening that I don’t understand.
Any and all help is greatly appreciated!
Joe Thompson
Engineer / Scientist
Electric Power Research Institute
Energy Storage and Distributed Generation
(912) 663-3407
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