esphome-dimplex-optimyst

ESPHome external component that turns an ESP32 into a virtual Dimplex Opti-Myst Pro remote. Bluetooth-advertises the same packets the physical 6-button remote sends, so the cassette can't tell the difference.

Confirmed working with the CDFI500-PRO and CDFI1000-PRO cassettes (Dimplex part numbers 6909660300 / 6909660400) used in the Opti-Myst Pro 1000 / Pro 1500 / GBF fireboxes. Tested in 2026 against firmware H:7.0 / S:6.1.

Not affiliated with Dimplex. Use at your own risk.

Usage

Add to any ESPHome config:

external_components:
  - source: github://victorgolfecho/esphome-dimplex-optimyst@main
    components: [dimplex_optimyst]

esp32_ble:
  io_capability: none

dimplex_optimyst:
  - id: cassette

button:
  - platform: dimplex_optimyst
    dimplex_id: cassette
    name: "Fireplace Power"
    cmd: POWER
  - platform: dimplex_optimyst
    dimplex_id: cassette
    name: "Sync to Cassette"
    cmd: SOUND
    duration: 25s

That's it. The component handles the raw BLE advertising; the button platform exposes a press that triggers it. See example.yaml for a full ready-to-flash config.

Configuration

dimplex_optimyst:
  - id: <required, used by button.dimplex_id>

The component has no further options today. It uses the ESP32's public MAC for all broadcasts.

Button platform

button:
  - platform: dimplex_optimyst
    dimplex_id: <id of a dimplex_optimyst entry>
    name: <button name>
    cmd: <see commands table below>
    duration: 250ms  # optional, default 250ms

Available cmd values:

cmd	Button on the physical remote
POWER	Power toggle
SOUND	Sound on/off (also used during pairing)
HEAT_ON	Turn on heater accessory
HEAT_OFF	Turn off heater accessory
MIST_UP	Bigger mist / brighter flame
MIST_DOWN	Smaller mist / dimmer flame

For pairing, expose a button with cmd: SOUND and duration: 25s. Press the cassette's Bluetooth-icon button (lights blink every 2.5 s), then press the long-Sound button in ESPHome's web UI within 20 seconds. The cassette beeps 4 times when it's accepted you as a remote.

Protocol

Each press emits an ADV_NONCONN_IND packet whose manufacturer-specific AD field is exactly 10 bytes:

4F 70   74 69 6D 79 73 74   <cmd>   08
"O p"   "t i m y s t"
↑       ↑                   ↑       ↑
└─ Company ID 0x704F (LE)   │       └─ trailer (always 0x08)
   placed by the BLE        │
   manuf-data AD field;     └─ command byte
   the rest is data

The cassette keeps a whitelist of remote MAC addresses, populated via its on-board sync mode. While in sync mode the cassette advertises Ooptimyst01<MAC> under company ID 0x4345 — handy to confirm sync mode is active from any BLE scanner.

One cassette accepts up to 5 remotes; one remote can talk to up to 5 cassettes. Because this component currently uses the ESP32's public MAC for every broadcast, all cassettes synced to it will react to every button press in lockstep (i.e. behaves as an "all on / all off" master). For independent per-cassette control, switch the address per command — not yet implemented in this component.

Hardware tested

• Cassette: Dimplex CDFI500-PRO (00B550), CDFI1000-PRO (00B510).
• Tethered controller: BLE name prefix FI (e.g. FI3919<Dimplex>).
• 6-button Opti-Myst Pro remote (power / sound / heat on / heat off / mist up / mist down).
• Firmware H:7.0 / S:6.1.

If your cassette is a newer Flame Connect-app variant which uses BLE GATT (not raw advertisements), this component will not work as-is. The community thread on Home Assistant discussions has notes on related models.

⚠️ Important: ESP32 chip revision matters

Use an ESP32 with revision v1.0 silicon. ESP32-D0WD revision v3.0 (also marketed as "ESP32-ECO3") boards have a bug in this BLE advertisement code path: esp_ble_gap_start_advertising returns success and the chip transmits scan requests fine, but advertisement packets either never hit the air or transmit at near-zero power. Cassettes don't see them. Verified across two different V3.0 modules from the same batch; both fail identically while V1.0 modules nearby broadcast strongly.

How to check what you have, plug the board into USB and run:

esptool.py --port /dev/ttyUSB0 chip_id

You're looking for:

• ✅ ESP32-D0WDQ6 (revision v1.0) — works
• ✅ ESP32-D0WD (revision v1.0) — works
• ❌ ESP32-D0WD-V3 (revision v3.0) — does NOT reliably broadcast

Sourcing V1.0 silicon is harder than it should be in 2026 — Espressif has shifted production to V3.0, and generic listings (e.g., Amazon "ESP-WROOM-32" / "ESP32 CH340C TYPE-C" boards) almost always ship V3.0 now. The boards look physically identical; the difference is only on the silkscreen on the chip itself.

To get V1.0 reliably:

• Buy through DigiKey/Mouser with explicit part numbers ESP32-WROOM-32D or ESP32-D0WDQ6.
• Or buy in bulk from cheap sources and screen with esptool.py on receipt; expect ~50% V3.0 to discard.

Alternatives worth trying if you want newer silicon and can iterate:

• ESP32-S3 modules — different chip family entirely, untested with this component but may sidestep the V3.0 BLE bug. Would also need framework adjustments (the YAML's board: esp32dev would change).

If your boards aren't broadcasting and esptool reports V3.0, the component code isn't the problem — it's the silicon.

Acknowledgements

The pOptimyst magic prefix and several command bytes were originally documented by the Home Assistant community (discussion #977) and an earlier ESPHome gist. This repository verifies them against the CDFI-PRO line, fills in the sync button (the cassette's Sound icon — silent in the manual due to a lost glyph), and packages everything as a drop-in ESPHome external component.