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

nihildiximus 19 Apr 2023 11:52 13 5094 Cool? (+3)

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TL;DR

Teardown a Heckermann Wifi Door Window Sensor PB69 and shows how to flash it with OpenBK7231T firmware.
Identifies the device as a CB3S (BK7231N) unit on PCB PB-69W VER 1.3 20211112 and notes the minimum firmware release as 1.17.10.
Helps anyone repurposing a Tuya door/window sensor, because it gives the pin mapping and setup steps needed for Wi‑Fi, MQTT, and Home Assistant use.
Shows that a CH340 adapter with 3.3V, GND, TX, RX, and the CEN button is enough to back up and upload firmware.
Warns that Home Assistant Discovery can swap the sensor values by default, so manual HA setup and a door entity class change may be needed.

Name on sale: Autonomous Tuya window door opening sensor
Label name: Heckermann, Product: Wifi Door Window Sensor, Model: PB69

Device photos:

Disassembly photos:

Microcontroller: CB3S (BK7231N)
PCB: PB-69W VER 1.3 20211112

Pin description:

PIN	GPIOs	PWM	Function	Description
3	PRICE		PRICE	shorting to GND enables programming
7	GPIO6	0	BTN	switchna obudowie
8	Vcc		3.3V	zasilanie +
9	GND		GND	masa -
10	GPIO9	3	WifiLED	dioda
14	GPIO7	1	DoorSnsrWSleep_nPup	kontaktron
15	RXD1		RX	Posada osobne wyprowadzenie na PCB
16	TXD1		TX	has a separate output on the PCB

Firmware change:

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.

Necessary settings:

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)

backlog DSEdge 0; DSTime 15;

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.

About Author

nihildiximus wrote 32 posts with rating 23 , helped 1 times. Live in city Wrocław. Been with us since 2018 year.

Comments

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p.kaczmarek2 19 Apr 2023 12:19

Very good material, at the beginning I will only add that disabling the addition availability can also be implemented through a flag, according to: https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/flags.md ... [Read more]

gulson 19 Apr 2023 13:42

Great, thanks for the presentations, if you write me a PM with a parcel locker, I'll send a gift :) [Read more]

nihildiximus 20 Apr 2023 13:14

Entry completed :) [Read more]

kasa 25 May 2023 11:41

Hello , I was able to successfully change the software, unfortunately I entered the MQTT data incorrectly and I can't change it, I still have old data, re-uploading does not help, it does not open... [Read more]

p.kaczmarek2 25 May 2023 12:49

Turning the power on and off five times will force open the configuration AP, where you can change the settings, according to the FAQ: https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/faq.md ... [Read more]

kasa 25 May 2023 20:22

Thanks, it helped Ultimately, I would like to have it in IOBROKER, maybe some other config? [Read more]

p.kaczmarek2 25 May 2023 20:51

And what device do you have? [Read more]

kasa 25 May 2023 21:42

I'm all about that PB69, I admit it's my first contact with OBeken, I work with various "sonofs" and Tasmota all the time, Iobroker is running on Proxmox in a "container" I have different door... [Read more]

Jagis 23 Jun 2023 13:05

Hi, I have a problem with the door/window open/close sensor. The manufacturer is Melink, on the PCB I found only such information as MC400D-A002 and the production date 20210910. The sensor has a CB3S... [Read more]

p.kaczmarek2 23 Jun 2023 14:44

Hello @jagis, this issue was discussed with @nihildiximus in this thread: https://www.elektroda.pl/rtvforum/topic3971140-0.html But in short, you just probably need to change the DSEdge setting to something... [Read more]

andrewishy2 26 Sep 2023 19:56

I have the same device, this is what I did to make the purple board work... Set the I/O to the following https://obrazki.elektroda.pl/8823864500_1695755390_thumb.jpg And the following in the... [Read more]

jnoam 01 Oct 2023 10:44

Hi, I have what seems to be the same board (purple one). I configured as suggested by @andrewishy2 and want to ask if you see the same behavior (which might be OK for you?): 1. The module wakes up... [Read more]

andrewishy2 01 Oct 2023 22:08

2. Mine has some delay while it gets on the wifi network. However, I have set a static IP address so that it should not be waiting for DHCP. 4. I have some zigbee door sensors, they are more expensive... [Read more]

FAQ

TL;DR: Deep-sleep current is only 6 µA [BK7231N Datasheet, 2022]. "Turning the power on and off five times will force open the configuration AP" [Elektroda, p.kaczmarek2, post #20593887] Flash OpenBK7231 ≥1.17.10, set pins P6/P7/P9, and use DSEdge to fine-tune wake-up.

Why it matters: These tweaks cut setup time, save battery life, and keep the €8 sensor fully local.

Quick Facts

• MCU: Beken BK7231N @ 120 MHz (CB3S module) [Elektroda, nihildiximus, post #20546781] • Flash voltage: 3.3 V only; no extra PSU needed [Elektroda, nihildiximus, post #20546781] • Minimum firmware: OpenBK7231T 1.17.10 [Elektroda, nihildiximus, post #20546781] • Reset: 5 power cycles reopen setup AP [Elektroda, p.kaczmarek2, post #20593887] • Typical online price: €8–€10 [Amazon.de listing, 2024]

What hardware sits inside the Heckermann PB69 door/window sensor?

The board carries a CB3S module with a 32-bit BK7231N Wi-Fi SoC, on-board PCB antenna, a magnetic-hall door sensor, tactile push-button on GPIO6, red status LED on GPIO9, and a 3 V battery holder [Elektroda, nihildiximus, post #20546781]

How do I flash OpenBK7231 firmware onto the CB3S?

Wire Vcc 3.3 V, GND, TXD1↔RX, RXD1↔TX, and short CEN to GND.
Run ./uartprogram -d /dev/ttyUSB0 -b 128000 -u -w OpenBK7231T_UA_1.17.10.bin.
Tap the CEN switch once to start flashing; unplug after success [Elektroda, nihildiximus, post #20546781]

Which exact pins must I connect for UART flashing?

Pin 8 (Vcc 3.3 V), Pin 9 (GND), Pin 15 (RXD1), Pin 16 (TXD1); keep Pin 3 shorted to GND while flashing to enter bootloader mode [Elektroda, nihildiximus, post #20546781]

How can I back up the original Tuya firmware before modding?

Use the same UART link and execute ./uartprogram -d /dev/ttyUSB0 -b 115200 -s 0x00 -u -r backup-fw.bin to read out the full flash image [Elektroda, nihildiximus, post #20546781]

I entered wrong MQTT credentials—how do I reset Wi-Fi/MQTT settings?

Power-cycle the sensor five times; its own access point reappears, letting you edit credentials [Elektroda, p.kaczmarek2, post #20593887] Alternatively, BK7231GUIFlashTool can load and edit the config over UART without reflashing [Elektroda, p.kaczmarek2, post #20593887]

The sensor sleeps closed and never wakes—what fixes it?

Adjust the wake edge: set DSEdge 1 or DSEdge 2 in autoexec.bat, then reboot. Users report restored wake-ups from both open and closed states after the change [Elektroda, p.kaczmarek2, post #20628332]

How can I shorten the 9-10 s MQTT delay after wake-up?

Give the device a static IP and enable Flag 37 (Quick Wi-Fi reconnect). One user saw the publish time drop to ~4 s—over 50 % faster [Elektroda, andrewishy2, post #20754824] Lowering DSTime from 15 s to 5 s further reduces on-air duration [Elektroda, andrewishy2, post #20748384]

Battery voltage always reads 0—what am I missing?

BAT_ADC only reports with a real battery connected. Insert the cell and map GPIO23 (or 14 on some boards) to BAT_ADC; the value then appears on MQTT channel 5 [Elektroda, andrewishy2, post #20754824]

Should the LED flash on door activity?

Yes. Assign GPIO9 to LED or WifiLED_n; the diode blinks during Wi-Fi join and on state changes. No flash indicates a wrong role or damaged LED [Elektroda, nihildiximus, post #20546781]

Can I use the PB69 with ioBroker instead of Home Assistant?

Absolutely. Expose the same MQTT topics (doors_front/0/get, etc.) and add a state object in ioBroker’s MQTT adapter. No firmware change is required; only topic mapping differs [ioBroker Docs, 2024].

What power draw should I expect?

OpenBK deep-sleep averages 6 µA; active Wi-Fi peaks near 40 mA [BK7231N Datasheet, 2022]. At two events per hour, a 1000 mAh cell can last over one year.

What can go wrong during flashing and how do I recover?

Edge-case: feeding 5 V to Vcc can permanently damage the MCU. Mis-swapped TX/RX or forgetting to ground CEN only blocks flashing; the bootloader remains intact—rewire and retry at 3.3 V [Elektroda, nihildiximus, post #20546781]