Owning a backyard pool means learning about chemicals, and dealing with covers, vacuuming, brushes and adjusting the thermostats and circuits. A saltwater pool makes things a bit easier, but you still need to keep an good eye on the system.

The OPNpool integrates the functionality of a traditional Pool Controller into the modern smart home. It keeps tabs on the status of the connected controller, pool pump and chlorinator. This provides not only a more convenient solution than physically interacting with the pool equipment, but the ability to create automations that runs the pump for a duration depending on the temperature.

Thanks to the people that reverse engineered RS485-based protocol, OPNpool can listen into the communication between the pool components. The ESP32 shares the resulting state information as JSON/HTTP and can publish it using MQTT. Last but not least, it integrates seamlessly with Home Assistant thanks to MQTT Discovery.

Credentials are provisioned using an Android app. It even supports over-the-air updates when you decide to hack the software!

OPNpool interface


  • Visualizes the status of the thermostats, pump, chlorinator, circuits, and schedules.
  • Allows you adjust the thermostats and toggle circuits
  • No physical connection to your LAN
  • Supports over-the-air updates
  • Easily one-time provisioning from an Android phone
  • Integrates with MQTT and Home Assistant
  • Accessible as a webapp
  • Protected with IP68 waterproof case and connectors
  • Does not require a power adapter
  • Open source!

This device was tested with the Pentair SunTouch controller with firmware 2.080, connected to an IntelliFlo pump and IntelliChlor salt water chlorinator.

This open source and hardware project is intended to comply with the October 2016 exemption to the Digital Millennium Copyright Act allowing “‘good-faith’ testing,” in a controlled environment designed to avoid any harm to individuals or to the public.

This open source project is hosted at

Continue reading to learn about the RS-485 bus access.

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