[BK7231N / CB3S] Teardown WiFi Smart Power Strip UK

gcole 588 7

Helpful post? (+1)

#1 10 Mar 2023 17:55

Here is a teardown for a generic WiFi Smart Power Strip UK Model no. SM-SO301K that I purchased by mistake from Amaozn UK Link to Amazon UK

I already have the Zigbee version and it works well with Home Assistant so I thought I'd try OpenBK with this one.

Disassembly was simple, rubber bungs on the back covering 8 small screws.

****NOTE****
Make sure you disconnect the device from any mains supply before opening the case and do not be tempted to plug it back in once you have removed the cover, ensure safe electrical working practices are carried out at all times.

The cover just prises off, there was no glue or concealed catches.

This is the main PCB and I have identified all of the relevant parts, you can see the CB3S module in the centre it uses the BK7231N chip.

There are four mains outputs, one 5V USB output, two separate LED indicators (red and blue) and one button input.

I temporarily soldered wires to the +3v3, Gnd, TXD and RXD pins on the CB3S module and attached them to a serial UART plugged into my Windows computer.
I downloaded the BK7231 GUI flasher tool from here, unzipped it and ran it.
I then clicked the button 'Download latest from web' and after downloading, selected that file to flash to the module.
Ive done this before so I selected the COM port of my Serial UART and opted to 'Do firmware write (no backup!)'
Once the flash procedure started I shorted CEN (Pin 3) to Gnd for a short pulse and the flash procedure continued to completion.

Head over to https://github.com/openshwprojects/BK7231GUIFlashTool for a detailed overview of how this tool works.

Confident that the procedure had worked, I desoldered my temporary wires and reassembled the device before plugging into the mains supply.

Once I'd got the WiFi settings completed and connected to my AP, I then set up the config as follows:

It worked great!

Well it didn't entirely, I found a bug with the Btn_tgl_all function but that was fixed overnight once I'd raised it on guthub.

Thanks for the amazing response!

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gcole gcole

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#2

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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#2 10 Mar 2023 18:08

There was indeed a little logical mistake in Toggle All button which manifested only when Relay channels are indexed starting from 1 and not 0, but it's now indeed fixed.
Very nice teardown, it's interesting to note that we had another power strip teardown recently, but the one below is using TuyaMCU:
[CB2S/BK7231N] TuyaMCU AOFO Smart Power Strip C733
So basically it looks like we have two different approaches to creating that kind od device from manufacturers. Some of them are using just WiFi module GPIOs, and some are integrating external MCU and TuyaMCU protocol...

Btw it seems your CB3S has still some unused GPIO, so it should be possible to connect some extras in the future, like a sensor or something, although I am not sure if such modification would make much sense in this case.

Btw can you also copy here JSON template from Web Application?

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600 and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

gcole gcole

Level 3

#3 10 Mar 2023 21:37

Here is the json config

{
  "vendor": "Generic",
  "bDetailed": "0",
  "name": "WiFi Smart Power Strip",
  "model": "SM-SO301K",
  "chip": "BK7231N",
  "board": "CB3S",
  "keywords": [
    "Mains Power Strip",
    "USB Power Supply",
    "4 Gang"
  ],
  "pins": {
    "6": "Rel_n;2",
    "7": "Btn_Tgl_All;0",
    "8": "Rel_n;1",
    "10": "Rel_n;6",
    "14": "Rel;5",
    "21": "WifiLED;0",
    "23": "Rel_n;1",
    "24": "Rel_n;3",
    "26": "Rel_n;4"
  },
  "image": "https://obrazki.elektroda.pl/4535041600_1678464108_thumb.jpg",
  "wiki": "https://www.elektroda.com/rtvforum/topic3963570.html"
}

#4

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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#4 10 Mar 2023 22:07

Thank you, the device has been added to our list.

https://openbekeniot.github.io/webapp/devicesList.html
If you have any other devices, feel free to submit them.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600 and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects
#5

gcole gcole

Level 3

Topic author Helpful post? (0)

#5 10 Mar 2023 23:24

Ive got some more devices coming soon so I will definitely add more in the future.

I have a question.

Looing at scripts and so on I'm wondering if tehre is a way to set up the behaviour in the following way.

Chanels 1 to 6 are relay outputs, I would like the following behaviour.

When any of Chanels 1 to 5 are set to on, chanel 6 is set to on
When Channels 1 to 5 are all set to off, chanel 6 is set to off.

Effectively channel 6 is an indicator that a relay is set to on.

If you can point me in the right direction I will appreciate it.
Thank you.
#6

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

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#6 11 Mar 2023 08:47

The similiar behaviour is present in one of our automatic firmware self-tests, designed to check the scripting functionality after each development iteration.
https://github.com/openshwprojects/OpenBK7231...rc/selftest/selftest_demo_buttonToggleGroup.c
Here's a related code fragment:
Code: c
Log in, to see the code

You can alter it to check if any other channel is on and then set a specific channel to 1 or 0 and then add it as a handler to all channels expect that one

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600 and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

gcole gcole

Level 3

#7 11 Mar 2023 15:40

I put this in an autoexec.bat file and it works exactly as expected, once again thank you!

alias set_led_on backlog setChannel 6 1
alias set_led_off backlog setChannel 6 0
alias myToggle if $CH1||$CH2||$CH3||$CH4||$CH5 then set_led_on else set_led_off
addEventHandler OnChannelChange 1 myToggle
addEventHandler OnChannelChange 2 myToggle
addEventHandler OnChannelChange 3 myToggle
addEventHandler OnChannelChange 4 myToggle
addEventHandler OnChannelChange 5 myToggle

#8

p.kaczmarek2 p.kaczmarek2

Moderator Smart Home

Helpful post? (0)

#8 11 Mar 2023 16:04

Thank you, is there anything else I may help with?

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600 and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects
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[BK7231N / CB3S] Teardown WiFi Smart Power Strip UK