Title: RD200 V3 (Firmware 3.0.1) – ESP_GATT_CONN_FAIL_ESTABLISH with ESPHome Bluetooth Proxy

[ottoberling-max]

Hello,
i have some problems with the radoneye.
I hope you can help me.

Device:

RadonEye RD200 V3, Firmware 3.0.1
Serial: FR:JK12RE001423
MAC: 88:57:21:A2:91:8A

Setup:

Home Assistant 2026.7.4
ESPHome 2026.7.3, ESP32 rev3.1
Bluetooth Proxy: Active, 3 connection slots
RSSI: -67 dBm (good signal, 4 meters distance)
rd200v2 HACS v5.03

Error:

custom_components.rd200_ble.config_flow
Failed to connect after 9 attempt(s): Error ESP_GATT_CONN_FAIL_ESTABLISH
Connection failed to establish

What I tried:

Phone rebooted, Ecosense app fully closed
RadonEye power cycled
ESP32 reflashed multiple times with clean config
ESPHome native radon_eye_rd200 component → Platform not found
scan_parameters adjusted (interval 320ms, window 30ms)

The device advertises correctly and is visible in HA Bluetooth scanner diagnostics as connectable. GATT connection always fails after 9 attempts. No connection ever established (connect_completed_total: 0).

Related: esphome/issues#6304, esphome/esphome PR#7962

Is V3 supported? Any workaround available?

[jdeath]

Issue #53 confirms 3.0.1 works. Be sure not using esphome component at same time. Perhaps revert to older version 4.8 , some people don't work with new version for an unknown reason