I have a Fujitsu unit and I’ve been looking for ways to control it using Home Assistant. There hasn’t been anything until I found this project: https://github.com/unreality/FujiHeatPump, someone actually cracked the protocol and released an Arduino library. Then I see the opportunity to finally contribute to the community.
Source code here:
I 3D printed a case for the circuit board now it looks better.
To avoid confusion:
If you use my code as-is, you need a Fujitsu wall controller acting as the “master” controller, our board is going to emulate a “slave” controller.
MCP2025 RXD(pin5) → ESP32 Serial2 RX (GPIO16)
MCP2025 TXD (pin6) → ESP32 Serial2 TX (GPIO17)
MCP2025 GND(pin3) → ESP32 GND (GND of AC controller, MCP2025 and ESP32 must be connected together)
I use a buck converter to convert the 12v to 5v for my ESP32.
You need to turn off the AC power and wait for the controller to go blank, before wiring anything. The AC and ESP32 need to be turned on at the same time, or the ESP should be powered on before the AC. If you see an error code on your controller, try power cycling it
And it seems like this also works for older Fujitsu AC controllers, see @miriumar reply in the thread.