Hello
I’m sorry for not answering before. I’ve been out working. I have tried several options from the datasheet and it has not worked. No message appears on the control.
I have found mcp2025-330 and mcp 2025-500 in Europe at a reasonable price, to test with nodemcu and esp32.
I am still interested in the project to add functions to my old air conditioner. Thank you very much
Cheers
I’m about to join you in this little project. I’ve written down the shopping list, and I understand all I need is:
Am I missing anything?
I have prior experience flashing Sonoff devices with custom firmwares, but it was centuries ago… Wish me luck!
Edited: Added buck converter to the list and clarified ESP32 type, as per Aaron’s reply.
You need something to power the board.
I use the 12v power from the controller and step it down to 5v for the ESP32.
I would suggest getting one of those buck converters, either fixed voltage or variable voltage, that’s probably the easiest way.
As for ESP32, I’d suggest you get an ESP32 development board that has USB built-in, that way you don’t need any other tools to flash it. Make sure you get the older ESP32 with 2 cores, the newer ones with a single core are not supported
Almost missed that; added to the list. Thank you Aaron!
Components ordered! The MCP2025 may take a couple of weeks to get here (ordered in Reichelt), but I’ll start tinkering with the ESP32 and Aaron’s code as soon as tomorrow.
In case it helps anyone, this is a (I think) suitable ESP32: https://amzn.eu/d/asmAFzm
This is exciting stuff 
.
(Editing here, as consecutive posts are not allowed)
Progress report!
In case it helps anyone, the wiring to the thermostat bus is as follows (according to Fujitsu’s service manual):
Red: 12V
White: Signal
Black: COM (ground)
Also, while awaiting delivery of the bus microcontroller, I’ve flashed the bare ESP32 board, without attaching any logic to its pinout. It doesn’t pass the setup step, entering an infinite reboot cycle, and not showing up in ESPhome - I assume this is normal, given that it can’t communicate with the thermostat bus?
Still awaiting delivery of the MCP2025, I’ve calibrated the buck converter to 3.3V, from the AC unit output (11ish V in my case).
I’ve put everything together on a prototyping board, with a placeholder component in place of the MCP, and started planning for the PCB. Attaching below, in case it helps anyone.
I just found this project. I am wondering: Why are single core ESP32 not supported? I have a GitHub - 01Space/ESP32-C3-0.42LCD sitting around that I was hoping to use. Is dual core a requirement for this project or is it just that I would have to change build settings?
Hey Andreas, I’ve not tested it on ESP32-C3. If ESPHome runs fine on it, the single-core version (it’s in a separate branch) might work.
In the master branch (multi-core version) I dedicate one core just to handle the serial communication. I think the AC unit wants the controller to always “ping” back reporting its health status or something, one time the WiFi went down, and the ESP32 spent quite a bit of time trying to connect to wifi, and probably the serial connection “missed” a beat, and the AC gave out error code on the main controller, and I had to power cycle it.
Hi. I have a fujitsu air and I want to remotely control it. I dicided to follow this project. First of all I want to buy the hardware required. On aliexpess I see a lot of esp32 boards, wroom, CAM, 32pin, 32U, 38 pin, etc … Can anybody helpme to choose the right one? Thank you.
Pd: I have a spare ttgo esp32 with lcd at home. Would do the job?
Hi @Sisku, I posted the shopping list (as well as a link to buy the same ESP32 I used) in one of my comments above, along with some diagrams.
It’s extremely simple to wire and set-up (both circuit and ESPhome config worked for me on the first attempt). The most “difficult” part is getting the MCP2025 chip delivered, as shipping to Spain took a bit longer than anticipated .
Edit: not sure if your ESP32 will be compatible, maybe someone else can help there. An important requirement is that it’s dual core, to avoid bus signal processing latency that could result in errors.
Thank you for sharing this info, I have purchased all the parts and started to assemble them on the breadboard. Managed to load the code, and setup Home Assistant - First time testing this sort of stuff, and looking forward to hooking it up next to the controller this weekend.
I noticed during compiling, I recieved the below errors, I have tried both git repo include the single core.
As well as the below:
I think these were warnings, not errors, did it fail to compile? Did you see a bin file after the compilation finishes?
Hi,
Thanks for your reply. Compiled till it said successful and bin file loaded ok - based on the logs I can see it connected to my wifi ok as fujitsu device.
And it Works!! Geez. 12 Midnight - What a time to try it.
Thanks Aaron!
Does anyone else’s every so often connection get interrupted?
Yes, the esp32 is sitting next to the wifi router.
This has something to do with your environment configuration, might be the board or the dependencies.
Hi all, I read with pleasure that there are a few people interested in this topic.
I will preface this by saying that I tend to use Homekit at home because it is much easier for my parents, consequently I have been using the Unreality repository to be able to command my unit.
Further premise: what I have made does not work on the software side, probably because the version of Homespan (the Homekit framework for ESP32) has changed and along with it the authentication part, plus Unreality does not have time to update everything so I am here with a really nice but not working harware. I, unfortunately, do not have the ability to update it properly because I am not familiar with the Homespan environment.
I am, therefore, pleased to share with you the PCB I designed in the hope that it will be of help to someone.
Here the last version of this project on GitHub: FUJI ATOM INTERFACE
Here I put a kind of BOM:
x1 10k Resistor: Yageo Thin-Film Resistor SMD, 10kΩ, 0805 (2012M), ±0.1%, 0.125W
[RS-Code: 198-5588] [Constructor Code: RT0805BRD0710KL]
x1 10uF Cap: Kemet MLCC, 0805 (2012M), 10μF, ±10%, 25V cc, SMD, X5R
[RS-Code: 891-9791] [Constructor Code: C0805C106K3PACTU]
x1 JST Connector 3-Pin: JST S3B-ZR (LF)(SN)
[RS-Code: 762-0774]
x1 LIN Transceiver: Microchip MCP 2025-330E/P Reichelt.com
x2 Header 4-Pin: Samtec TSW-104-07-G-S-LL Samtec.com
x1 Header 5-Pin: Samtec TSW-105-07-G-S-LL Samtec.com
x1 (4.5V-24V) to (1.8-12V) DC-DC Adjustable Mini Buck Converter: Amazon.it
I hope you are pleased with it
Thank you very much! This looks so professional! I’ve been meaning to do this but never have the time to learn PCB design.
Well done, this looks of high quality - You can sell that!
