[harg]

I wonder if it would be possible to figure out which pins are connected to what on the device's board and just flash the thing completely with ESPHome and write a custom yaml config for it, rather than adapting the existing vendor firmware.

[ddeck]

It's certainly possible. Tracing the MCUs IO lines to LEDs/buttons/relays etc on a PCB is usually pretty straightforward.

I have just finished doing this and writing replacement firmware for the Aqara E1 series of Zigbee switches, after getting fed up with them not supporting basic Zigbee binding functionality.

[wezdog1]

Amazing. I have the Aqara Z1s and it has the SI labs MG24 chip. Ive always wanted to reflash it because I believe it supports thread at a hardware level.

[alright2565]

It would be really easy. I'm not sure why the author has gone through so much effort to hide what filter this is, but I'm assuming J2 is the blower power output and J3 is touchpad controls.

I've done exactly this on my own air filter, and it's about 200 lines of config. The hardest part is mapping binary outputs to a percentage:

    switch:
      - platform: gpio
        pin: GPIO21
        id: fan_low
        interlock_wait_time: 250ms
        interlock: &interlock_group [fan_low, fan_mid, fan_high, fan_turbo]
      - platform: gpio
        pin: GPIO25
        id: fan_mid
        interlock_wait_time: 250ms
        interlock: *interlock_group
      - platform: gpio
        pin: GPIO22
        id: fan_high
        interlock_wait_time: 250ms
        interlock: *interlock_group
      - platform: gpio
        pin: GPIO17
        id: fan_turbo
        interlock_wait_time: 250ms
        interlock: *interlock_group
    output:
      - platform: template
        id: fan_speed_output
        type: float
        write_action:
          - lambda: |-
              id(fan_low).turn_off();
              id(fan_mid).turn_off();
              id(fan_high).turn_off();
              id(fan_turbo).turn_off();
              auto light = ((AddressableLight*)id(status_light).get_output());
              for (int i = 6; i <= 9; i++) {
                light->get(i).set(Color::BLACK);
              }

              if (state < 0.24) {
              } else if (state < 0.26) {
                id(fan_low).turn_on();
                light->get(6).set(Color(255,0,0,0));
              } else if (state < 0.51) {
                id(fan_mid).turn_on();
                light->get(7).set(Color(255,0,0,0));
              } else if (state < 0.76) {
                id(fan_high).turn_on();
                light->get(8).set(Color(255,0,0,0));
              } else {
                id(fan_turbo).turn_on();
                light->get(9).set(Color(255,0,0,0));
              }
              light->schedule_show();

    fan:
      - platform: speed
        name: "Filter Speed"
        output: fan_speed_output
        speed_count: 4
        id: my_fan

[stereo]

On top of that, it looks like it would be relatively easy to spoof the cloud server and make the device believe that there is a firmware update available to then feed it esphome, a bit like the switchbota hack.

[MadnessASAP]

That would've been my go-to, and has been with most of the other "smart" devices in my house.