[CB3S/BK7231N] Heckermann Wifi Door Window Sensor, Model: PB69 - teardown, chang

CH340 converter is enough to change FW. We connect Vcc 3.3V, GND and TX and RX interchangeably. I didn't need an additional power source during development. A switch should be connected to the CEN and GND pins, which, when pressed, will enable downloading or uploading the FW.




Download the firmware from the address: https://github.com/openshwprojects/OpenBK7231T_App/releases
Minimum version required. 1.17.10

I had problems with BK7231GUIFlashTool under linux via mono so I took advantage of hid_downloader_py .

1. To make a firmware backup :


2. To upload new firmware :


After running the command, you need to briefly press the button connected to the CEN to start programming. After all, just unplug the device, insert the batteries, connect to the new Wifi AP and start configuration via www.



We connect to the Access Point of the device via Wifi and enter the configuration page: http://192.168.4.1

We set in turn:

1. Wi-Fi → Configure WiFi ( after confirming, we need to reconnect via the address taken from DHCP )

2. Static IP address to speed up connection → Configure IP

3. Sensors → Configure module :

P6	Btn
P7	DoorSnsrWSleep_nPup
P9	LED

4. Flags → Configure general/flags :

x	35 [HASS] Deactivate avty_t flag for sensor when publishing to HASS (permit to keep value). You must restart HASS discovery for change to take effect.
x	37 [WiFi] Quick connect to WiFi on reboot (TODO: check if it works for you and report on github)

5. Start commands → Change startup command text : (we set the same wake-up state for each position and shorten the time to fall asleep)

6. Device name → Configure names

7. Connection to MQTT → Configure MQTT

8. Home Assistant settings→ Home Assistant Configuration



You can use Home Assistant Discovery to automatically add a sensor to the MQTT service, but by default the sensor values are swapped:


Instead, we create a file with the sensor ourselves and add it manually to the HA configuration:



And in HA itself, we change the entity class to "door" to improve the way it is displayed.