I have Fuji Electric AC units at home that I wanted to become integrated with my smart home network. Unfortunatelly, those are old-school devices with IR and wired remotes and no WiFi.
This package contains a simple daemon that will convert serial interface of the AC unit into RPC service. In order to use it, you will need a device capable of handling UART @ 500bps (author of the code used Raspberry Pi Zero). Release package contains pre-compiled ARM package suitable to use with Raspbian.
Hardware directory contains schematics and PCB design of a Raspberry PI Zero hat that interfaces directly with the AC Unit main board. It effectively replaces UTY-TWBXF module. Hat converts 400V DC available on the mainboard into 5V DC necessary to power up Raspberry PI and converts Tx/Rx logic. PCB dimensions make Raspberry Pi Zero + Hat fit the AC unit internal space so that entire device is WiFi enabled without any extra cables.
If you want to run this on ESP32 or Arduino, there is another library based on this work ported by unreality into smaller package and available here: https://github.com/unreality/FujiHeatPump
This software was tested against RSG09LUCA and RSG12LUCA and should interface well with Fuji Electric/Fujitsu Air conditioners that are using UTY-RNNUM, UTY-RNNXM or similar controllers.