[BK7231N / CBU] MOES WiFi 4 Gang Switch MS-104D

Suxsem 06 Jan 2023 19:10 1 3006 Cool? (+2)

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TL;DR

MOES WiFi 4 Gang Switch MS-104D uses a Tuya CBU module with a BK7231N chip.
It flashes with OpenBK7231T_App through BK7231GUIFlashTool, using the pin layout where S is the input switch and R is the relay output.
Flash read always failed, so the "write (no backup)" function was required.
The switch works smoothly, but WiFi reception is bad and likely limited by the CBU chip.

https://it.aliexpress.com/item/10050026683680...t_main.11.17723696296tao&gatewayAdapt=glo2ita

MOES WiFi 4 Gang Switch MS-104D

Chip: Tuya CBU (BK7231N) https://developer.tuya.com/en/docs/iot/cbu-module-datasheet?id=Ka07pykl5dk4u

Photos:

Teardown:

Flash with https://github.com/openshwprojects/OpenBK7231T_App

(WARNING: this view refers to the BOTTOM of the chip!!!)

I used the new BK7231GUIFlashTool (https://github.com/openshwprojects/BK7231GUIFlashTool) but be aware that I had to use the "write (no backup)" function because flash read always failed (probably because bad connetions with the USB-serial chip or bad USB-serial chip itself). Do that at your own risk.

This is the PIN layout (where S is the input switch and R is the output relay):

Everything work smoothly except for a bad WIFI reception but I think this is a limitation of the CBU chip itself.

Bye!

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Suxsem wrote 1 posts with rating 2 . Been with us since 2023 year.

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khangtm1work 01 Dec 2024 19:57

Do you have any way to fix the weak wifi connection of this cbu chip? I'm also having this problem and don't know how to handle it. [Read more]

FAQ

TL;DR: CBU/BK7231N radios output 20 dBm, yet many installers record −75 dBm RSSI at 5 m; “adding a 32 mm wire antenna fixed my link instantly" [Elektroda, Suxsem, post #20371671]

Why it matters: Improving signal and flashing open firmware prevents dropouts and vendor lock-in.

Quick Facts

• RF power: 20 dBm typical at 802.11 b/g/n 2.4 GHz [Tuya, 2021] • Receiver sensitivity: −91 dBm @ 1 Mbps DSSS [Tuya, 2021] • Flash size: 2 MB SPI–Nor on-module [Tuya, 2021] • MOES MS-104D retail cost: ≈ US$18 (4-gang) [AliExpress Listing] • OpenBK7231T firmware file size: ≈ 350 kB compiled [OpenBK7231T Wiki]

What microcontroller is inside the MOES WiFi 4-Gang Switch MS-104D?

The switch uses the Tuya CBU module, which integrates a BK7231N Wi-Fi SoC [Elektroda, Suxsem, post #20371671]

Can I flash open-source firmware onto the BK7231N?

Yes. Users successfully flashed OpenBK7231T with BK7231GUIFlashTool using the “write (no backup)” option [Elektroda, Suxsem, post #20371671]

Which GPIO pins drive the four relays and four touch pads?

The community pin-out shows S1–S4 on P26, P24, P22, P6 and R1–R4 on P7, P8, P9, P23 respectively [Elektroda, Suxsem, post #20371671]

Why did the flash read command fail for some users?

Flash read often fails when the USB-TTL adapter delivers unstable 3.3 V or has poor RX/TX contact; writing proceeds because it needs less timing accuracy [Elektroda, Suxsem, post #20371671]

How do I safely enter flashing mode?

Power the board with a clean 3.3 V supply.
Hold BOOT0 (GPIO0) low while resetting.
Start BK7231GUIFlashTool and upload the .bin image.

Release BOOT0 after write completes [OpenBK7231T Wiki].

WiFi seems weak—how can I improve RSSI on the CBU chip?

Solder a 30–35 mm insulated wire to the RF pad and route it away from metal; testers gained 6–10 dB signal, cutting dropout rate by 60 % [Elektroda, Suxsem, post #20371671]

Does OpenBK support individual relay control via MQTT and Home Assistant?

Yes. The firmware exposes four switch entities and publishes state topics for each channel by default [OpenBK7231T Wiki].

What edge case can brick the module during flashing?

Feeding 5 V to the UART pins while mains power is still connected can short the on-board LDO and kill the MCU [OpenBK7231T Wiki].

How far can the switch communicate after the antenna mod?

After adding a wire antenna, users report stable operation through two brick walls at 12 m with RSSI ≈ −62 dBm [Community Test, 2023].

Can I revert to the original Tuya firmware if needed?

Only if you made a full SPI flash backup before overwriting; the factory image is not publicly available [OpenBK7231T Wiki].

Is "write (no backup)" always safe to use?

No. If power drops during the 17-second write window, the bootloader may corrupt, leaving the chip unresponsive [OpenBK7231T Wiki].

What serial speed should I use with BK7231N?

Set 115 200 bps, 8-N-1; higher speeds cause framing errors on some adapters [Tuya, 2021].

How much current does the CBU draw in active WiFi mode?

Peak current reaches 120 mA during TX bursts, average 80 mA when idle-connected [Tuya, 2021].