Here the final PCB & schematic. Very basic...

Let's go to HomeAssistant now.

First add this to configuration.yaml

climate:
  - platform: mqtt
    name: "Clim grand mur"
    unique_id: "clim_1"
    modes:
      - "off"
      - "heat"
      - "dry"
      - "cool"
#     - "auto"
    swing_modes:
      - "on"
      - "off"
    fan_modes:
      - "auto"
      - "high"
      - "medium"
      - "low"
      - "silent"
    power_command_topic: "device_7/cmnd/POWER"
    mode_command_topic: "device_7/cmnd/OPMODE"
    mode_state_topic: "device_7/STATE"
    mode_state_template: '{{ value_json.op_mode }}'
    temperature_command_topic: "device_7/cmnd/TEMP"
    temperature_state_topic: "device_7/STATE"
    temperature_state_template: '{{ value_json.temperature }}'
    fan_mode_command_topic: "device_7/cmnd/FAN"
    fan_mode_state_topic: "device_7/STATE"
    fan_mode_state_template: '{{ value_json.fan_speed }}'
    current_temperature_topic: "device_7/STATE"
    current_temperature_template: '{{ value_json.room_temp }}'
    swing_mode_command_topic: "device_7/cmnd/SWING"
    swing_mode_state_topic: "device_7/STATE"
    swing_mode_state_template: '{{ value_json.swing_mode }}'
    max_temp : 32
    min_temp : 16
    precision: 1.0
    availability_topic: "device_7/LWT"
    payload_available: "Online"
    payload_not_available: "Offline"

and the card setup :

type: custom:thermostat-card
entity: climate.clim_grand_mur
title: Clim grand mur
step: 1
no_card: false

Here the result :

HVAC OFF :

HVAC in COOL mode

HVAC mode list :

Here the main HVAC_status object that containts all properties (even those I not understood...)

struct HVAC_status {
    word power;        //power (on, off)
    word op_mode;        //mode (auto, hot, dry, cool, fan)
    word fan_speed;        //fan speed (auto, high, medium, low, silent)
    word temperature;    //temperature (16~32°C)    
    word param_6;        // ?
    word param_11;        // ?
    word param_12;        // ?
    word swing_mode;    //swing mode (on, off)
    word room_temp;        //room temperature
    word param_102;        // ?
    word param_201;        // ?
//    word param_300;        // ?
    word param_301;        // ?
    word param_302;        // ?
//    word param_304;        // ?
//    word param_800;        // ?
//    word param_900;        // ?
} Hitachi_status;

Here the mode list and fan_list table.

const char mode_list[10][10] = {
    {"off"},        //0x0000
    {"heat"},        //0x0010
    {"dry"},        //0x0020
    {"-"},
    {"cool"},        //0x0040
    {"fan_only"},            //0x0050
//    {"auto"},        //0x8000
    {"auto_heat"},            //0x8010
    {"auto_dry"},            //0x8020
    {"-"},
    {"auto_cool"},            //0x8040
};
const char fan_list[5][7] = {
    {"auto"},        //0x00
    {"high"},        //0x01
    {"medium"},        //0x02
    {"low"},        //0x03
    {"silent"},        //0x04
};

I add 2 timers to trigger :

- HVAC write/scan : write to HVAC if neede or ask for status

- Send MQTT to HomeAssistant

/********************* Function management *****************/ 

if (millis()-scan_timer_counter > scan_timer) {
    scan_timer_counter = millis();  
    if(things_to_write){                                            // write to HVAC id request by callback
        set_HVAC(0x0800,0x07, false);                                // Enter setup mode
        set_HVAC(address_list[1], Hitachi_status.op_mode, true);    // Op mode
        set_HVAC(0x0300,0x0000, true);                                // Unknow
        set_HVAC(address_list[3], Hitachi_status.temperature, true);// desired temp
        set_HVAC(address_list[1], Hitachi_status.op_mode, true);    // Op mode
        set_HVAC(0x0300,0x0000, true);                                // Unknow
        set_HVAC(address_list[3], Hitachi_status.temperature, true);// desired temp
        set_HVAC(address_list[2], Hitachi_status.fan_speed, false);    // fan speed
        set_HVAC(address_list[4], Hitachi_status.swing_mode, false);// swing mode
        set_HVAC(address_list[0], Hitachi_status.power, false);        // power
        set_HVAC(0x0006,0x00, false);                                // Unknow
        set_HVAC(0x0007,0x00, false);                                // Unknow
        things_to_write = false;                            // done 
        delay(500);                                            // wait a while before send status
        request_HVAC_status();                                // read status
        Send_fct();                                            // send status to HA      
    } else {                                                // read from HVAC en send if needed
        request_HVAC_status();
        if (need_to_send_MQTT) Send_fct();                    // send status to HA
        need_to_send_MQTT = false; 
    }
}

/********************** Function send **********************/ 

if (millis()-send_timer_counter > send_timer) {
    send_timer_counter = millis(); 
    Send_fct();                                            // send status to HA
}

I choose finaly to communication with HomeAssistant via the MQTT integration. 

MQTT is extremely light and reliable  for this purpose.

I'll add also a custom thermostat-card. I'll show you this late...

Here me MQTT communication protocol : 

I also add a frequently a STATE information in JSON format 

device_7/STATE :
{"power":"OFF","op_mode":"off","swing_mode":"off","fan_speed":"auto","temperature":21,"room_temp":22,"RSSI":-55}

and a MQTT last will message to be able to check if the device is on or offline.

device_7/LWT :
Online

After a huge summer break, I'm back to finalize this project.

Next step is to write a simple sketch to be able to communicate with the HVAC. With a wemos D1 mini it's quite easy and with a telnet communication you can follow the communication remotely.

You need the SoftwareSerial library setup to :

	HVACSerial.begin(9600, SWSERIAL_8O1, 13, 14, false);		// baud raute: 9600, data size: 8 bits, parity: odd, stop bits: 1, RX:D7=13, TX:D5=14

 I need some additionnal resistors to dop the serial input from 5V to 3.3V to be compliant with ESP8266.

After many hours spend to snif the paquets here the first sharing. It was quite easy so far with the basic functions. I found 7 commands/informations out of 15. I add my investigation file

First we can find below the regular exchanged paquets every 6 sec. (Without any command)

Send by the SPX-WFG01 :

The A/C feedback

And now the command

So to here the list of adresses and content that I was able to catch.
 

There are still some question marks that have to be confirmed. And also 8 unkown information in the paquet. Maybe you have an idea ?

There are some functions that combined several of the command.

• The Leave Home function swith the A/C in heating mode, with 10°C  and Low fan
• Auto operating mode switch Operating mode and fan mode to auto

In addition, all the timer functions are managed by the the remote control itself. So only the basic commands (On/Off) are send by the remote control as scheduled previously.

According to the Hi-humo App description I should find also adresses releated to alarm functions. At this stage I'm not able to figure out how to trigger any alam from the A/C

First thing first

Here the first analysis of the serial communication between the SPX-WFG01 and the A/C catch with 2 serial adaptators connected to my laptop.

The communication consist of ;

- A paquet sent by the gateway containing 15 lines starting with MT, where P is the adress.

- The response from the gateway containing 15 lines starting all with OK and where P is the containt at this adress.

My assumption is that the last line (adress 0900) contains the A/C serial n° (hidden)

in addition :

• - Carriage return is 0x0D 0x00
• - C is simply = P XOR 0xFF

Now start playing ...

I connect my smartphone to the Hi-humo app and try to catch some commands between

In this case a very diffrent paquet is sent to the A/C containing 12 lines staring all with ST, P contains the adress followed by the value.

4 adress are missing and one (0007) is not only use in this message frame. I noticed that some adress are used several time in the same paquet and the adress sequence is also not the same.

If everything works well the A/C should asnwer
At this stage I noticed that the communication for this A/C unit is very similar to the one used and hacked by Florian in this project (thks to him). There are more containt, more lines in the paquet and probably at the end more function to manage.

One setp further !

I made some additionnal test with the IR remote control. Of course since the receiver is located directly inside the A/C housing the communication will not pass through the SPX-WFG01 and I'll not be able to get the content.
But the good news is that the  the A/C continues to send the ACK on his serial port so I was able to made some interesting comparisons.

... stay tuned !

My first step was to open the gateway and to check the pinout.

I can confirm the pinout posted by Florian (https://hackaday.io/project/168959-let-me-control-you-hitachi-air-conditioner)

Nevertheless the function of pin N°6 is still unclear for me. Let's check that later.

I mesured 5V for Rx & Tx echanges.

Every thing is ready to use my own tools that I've made to monitor and hack serial communication.

I'll come up soon with the first paquets...