[BK7231N/CBU] WiFi Modemix MOD003 Dual Light Controller

It's time for a review and release from the cloud of another small module for the box, this time offering control of two relays via WiFi, additionally allowing you to connect two switches to them. The module described here was bought in our country this time, so there was no waiting for shipping, but it cost a bit more than the gadgets imported straight from China, although it was not as expensive as in the case of other products, including the recently described RR400W , which for PLN 70 offers only one relay and without the possibility of connecting an external button (unless we load OpenBeken, then you can configure the pins at will and you can connect an additional button / sensor that was not planned by the manufacturer).
The topic will only cover the interior and the firmware change. As usual - I skip the Tuya application and immediately look inside.

Buying a kit
One of my readers gave me the set ( Thank you very much! ) so that I can change the firmware for it. As far as I know, such a driver can be purchased in several places on the Polish Internet, e.g. on a popular auction site. It is quite expensive, all PLN 70, but at least it can handle two lines - it has two relays inside.

assembly diagram:

Dimensions: 46x46x18mm
Before buying, check whether it fits our box and whether we will have a way to lead wires to it.

Kit contents
This time the set is quite poor. We don't even get screws or even a strip of double-sided tape for fixing. Pity.

Enough of the introduction, let's take a look inside.

MOD003 interior
As usual, it is enough to pry the casing. No screws.

Inside, you can see the LDO 1117 3.3V regulator and the KP15051SP transformerless converter controller.



Now you need to pull out the PCB. This time it comes out quite hard, it looks like there is a plate on the plate and something hooks.
What is it that hooks?

The extra PCB with the CBU module hooked up. Interestingly, the pairing LED and the pairing button are on this additional board. Goldpins, ground, power supply and inputs for two buttons and outputs for two relays go from this board.
Looking under this PCB, we can see the signal markings:

The description of the CBU is also on the web...

MOD003 programming
Here is the full list of connections required for programming and hardware configuration after OpenBeken has been uploaded:

CBU Pinout:

Quote:

pin number	Symbol	I/O type	functions
1	P14	I/O	Common GPIO, which can be reused as SPI_SCK (Correspond to Pin 11 of the IC)
2	P16	I/O	Common GPIO, which can be reused as SPI_MOSI (Correspond to Pin 12 of the IC)
3	P20	I/O	Common GPIO (Correspond to Pin 20 of the IC)
4	P22	I/O	Common GPIO (Correspond to Pin 18 of the IC)
5	ADC	I/O	ADC, which corresponds to P23 on the internal IC (Correspond to Pin 17 of the IC)
6	RX2	I/O	UART_RX2, which corresponds to P1 on the internal IC. (Correspond to Pin 28 of the IC)
7	TX2	I/O	UART_TX2, which is used for outputting logs and corresponds to P0 of the internal IC (Correspond to Pin 29 of the IC)
8	P8	I/O	Support hardware PWM (Correspond to Pin 24 of the IC)
9	P7	I/O	Support hardware PWM (Correspond to Pin 23 of the IC)
10	P6	I/O	Support hardware PWM (Correspond to Pin 22 of the IC)
11	P26	I/O	Support hardware PWM (Correspond to Pin 15 of the IC)
12	P24	I/O	Support hardware PWM (Correspond to Pin 16 of the IC)
13	GND	P	Power supply reference ground
14	3V3	P	Power supply 3V3
15	TX1	I/O	UART_TX1, which is used for transmitting user data and corresponds to Pin 27 of the IC. For the MCU solution, please refer to CBx Module.
16	RX1	I/O	UART_RX1, which is used for receiving user data and corresponds to Pin 26 of the IC. For the MCU solution, please refer to CBx Module.
17	P28	I/O	Common GPIO (Correspond to Pin 10 of the IC)
18	CEN	I/O	Reset pin, low active (internally pulled high), compatible with other modules (Correspond to Pin 21 of the IC)
19	P9	I/O	Common GPIO (Correspond to Pin 25 of the IC)
20	P17	I/O	Common GPIO, which can be reused as SPI_MISO (Correspond to Pin 14 of the IC)
21	P15	I/O	Common GPIO, which can be reused as SPI_CS (Correspond to Pin 13 of the IC)
test point	CSN	I/O	mode selection pin. If it is connected to the ground before being powered on, enter the firmware test mode. If it is not connected or connected to VCC before being powered on, enter the firmware application mode. Correspond to Pin 19 on the internal IC.

Here are the soldered wires - RX, TX, GND and 3.3V:

Ready circuit with LDO 3.3V and USB to TTL converter:

We program with this:
https://github.com/openshwprojects/BK7231GUIFlashTool
It is important for this device to first disconnect 5V from the LDO, then connect the USB to TTL converter to the computer, then start the flashing procedure (Getting Bus), and then connect the power supply (then the Getting bus will be successful and the proper reading / uploading of the firmware will start) .
In summary, the pins are:
- P7 - WiFi LED
- P9 - Relay 1
- P17 - Relay 2
- P8 - pairing button (from the housing)
- P24 - Switch 1
- P26 - Switch 2
Same with OpenBeken JSON format:

If we want to connect a bistable button, then in OBK we use the role of TglChannelOnToggle, and if a momentary button, then Button.
OpenBeken Documentation:
https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/README.md
Repository:
https://github.com/openshwprojects/OpenBK7231T_App

Summary
All in all, it wasn't that difficult, it was enough to solder 4 wires and the firmware change was successful. The module is quite nice, and the RX and TX outputs can then be used as regular GPIOs and, for example, connect DHT11 or SHT30 and additionally configure it in OpenBeken to send results to Home Assistant. It's just a few clicks in the web panel of the new firmware. Of course, you have to be careful, because the power supply on board does not provide galvanic separation, but this is the norm for this type of product. The possibilities after changing the firmware are really great.
There is also the issue of price - this time it was not as bad as in the case RR400W , but it's still hard not to notice that the classic Aubess Smart Switch directly from China can be up to two times cheaper, screenshot from the auction in the spoiler:

So I don't know if I can recommend a product from the theme. I also tested the cheapest Aubess from Aliexpress and I know that it works well with OpenBeken, but one thing should be remembered: after changing the firmware, we must make sure that we use the option PowerSave , i.e. from dynamic energy saving, otherwise the budget power supply from the deck will simply fail over time and you will have to replace the capacitors, as I described here:
How to fix a smart device that crickets, squeaks and makes strange noises?
In OpenBeken, just type PowerSave 1 in Startup Command and this will activate low power mode after every reboot.
That's it for now, thank you to a friend from outside the forum for giving me another product to review . After uploading the firmware, the product returned to the donor so that he could enjoy the ability to control the light without the Tuya cloud, all 100% locally, from the Home Assistant level.