esphome-della-ac

Local Home Assistant control for the Della 048-MS mini split

ESPHome firmware that exposes a Della 048-MS mini split as a full Home Assistant thermostat — no cloud, no Tuya account. It replaces the stock Wi-Fi dongle with an SMLIGHT SLWF-01 running this firmware, plug-and-play with the Della's USB-A service port.

The Della 048-MS does not speak the TCL protocol its USB port suggests — it is an AUX OEM unit speaking the AUX HVAC serial protocol at 4800 baud, 8E1, on an open-drain line. (Sampling that line at the obvious 9600 baud yields a convincing but bogus byte stream; that aliasing trap is why earlier attempts never worked.) The full story and byte-level map are in docs/PROTOCOL.md.

• Full climate entity — off / cool / heat / dry / fan-only / heat_cool, fan auto / low / medium / high / quiet, vertical / horizontal / both swing, boost (turbo) and sleep presets, current temperature and HVAC action
• Feature controls — Home Assistant entities for the panel display, health (ionizer), eco, self-clean and the anti-fungus dry cycle, each mapped to the remote's real behaviour — the off-state-only functions (self-clean, anti-fungus) are handled as such instead of no-op toggles
• Telemetry & status sensors — evaporator-coil, compressor and outdoor temperatures, inverter power %, the live blower speed, a typed setpoint sensor, and a one-line human-readable status summary
• Robust RX — receives over a pulse-capture path that is immune to the AC MCU's ragged rising edges, then reconstructs and CRC-checks every frame on-device
• Safe writes — each command is built by copying the unit's latest status frame and changing only the requested fields, and is refused if the last readback is stale
• 1 Hz state — sub-2-second updates in Home Assistant; bus load stays light
• Local only — native ESPHome API + OTA; nothing leaves your network

• A Della 048-MS mini split (other AUX-built Della / AUX-OEM units likely work — see docs/PROTOCOL.md).
• A SMLIGHT SLWF-01 (ESP-12F). It drops straight into the indoor unit's USB-A service port and already carries everything the link needs — the USB-A header, 5 V regulation, and the level shifting between the ESP8266's 3.3 V logic and the AC's 5 V TTL UART (AC-side UART on GPIO12 = TX, GPIO14 = RX). No wiring, no extra parts.
• DIY or other ESP8266 boards are likely supported, but you would have to provide that same supporting circuitry yourself — there is no reference design here. The SLWF-01 is the simple path.
• The service port is a 4-pin 5 V TTL UART, not a USB device — do not plug it into a computer.

A pre-built, secret-free image is published with each release. Plug the SLWF-01 into your computer over USB and install it from your browser (Chrome/Edge), or download della-ac-esp8266.factory.bin and flash it with esptool.py write_flash 0x0 della-ac-esp8266.factory.bin.

On first boot the dongle has no Wi-Fi. Give it yours either way: the browser flasher offers a Configure Wi-Fi step right after install (over the same USB-C link), or join the AC-wifi hotspot it raises (password slwf01pro) and pick your network in the captive portal. Then move the dongle to the AC's service port and adopt it in Home Assistant — set your own API key and OTA password when you do.

Once it's on your network, a debug dashboard (entity states + live logs) is served at the device's IP.

1. Install ESPHome (2026.5.3 known-good).
2. Copy the secrets template and fill it in: cp secrets.yaml.example secrets.yaml.
3. Flash (USB the first time, OTA thereafter): esphome run della-slwf.yaml.
4. Accept the device the ESPHome integration auto-discovers in Home Assistant; the Della AC climate entity and telemetry sensors appear on its device page.

Both builds share della-ac.base.yaml — della-slwf.yaml adds your secrets, della-ac.factory.yaml is the secret-free release image.

Receive is handled by an ESPHome remote_receiver capturing raw pin timings, which a lambda reconstructs into 4800-baud 8E1 bytes and CRC-validates. A tiny local component (components/della_ac/) maps those bytes onto a Home Assistant climate entity and builds outgoing commands. Keeping the protocol logic in the YAML lambda and only the HA-thermostat shell in C++ is deliberate — see docs/PROTOCOL.md for the framing, field maps, CRC, and the quirks the firmware compensates for.

• GrKoR/AUX_HVAC_Protocol and GrKoR/esphome_aux_ac_component — the AUX protocol documentation and reference implementation this work builds on.
• dudanov/iot-uni-dongle — dongle hardware reference.