[BK7231N/CB2S] Inverted PCB layout of CB2S on FS-05R Mini Dimmable Switch

Question

I bought a couple of cheap Aliexpress Mini Dimmable (FS-05R) switches, hoping to either flash OpenBeken, or at worst replace the CB2S with an ESP alternative. PCB model: FL-S117A-V2.2 Having desoldered the CB2S and connected to a USB-TTL there was no response to the BekenWriter and no amount of...

p.kaczmarek2 · Accepted Answer

Yes. I know this issue. I have experienced it myself already at least two times before. For example, in this topic: which is, actually, also about the FS-05R. The silkscreen on this device is incorrect. You need to ignore that. You need to assume the classic pinout like on Tuya docs:

p.kaczmarek2 · Accepted Answer

It does not work when wired as in the manual?

iotflasher · Answer

Oh wow.
So simple, so logical and yet, I don't think I would have thought of this myself.

But for anyone with the problem in the future....ignore the screen print, go with the connections as per datasheet.

Thank you, and you've also just solved the next step of figuring out the TuyaMCU comms with your link.

p.kaczmarek2 · Answer

I am happy to hear that it helped. I was also very confused at first, but then I remembered the good way to check the silkscreen - investigate the power connection on the PCB. Once you investigate how is 3.3V and GND connected, you will clearly see that silkscreen is invalid.

Let me know if my script for this dimmer works for you

iotflasher · Answer

The autoexec.bat script worked beautifully.
A simple copy paste from your post and the dimmer worked as should.
Thank you

I did also add a couple of features (double click, click hold, etc) for the buttons.
Making it work reliably from remote, as from local.

My final autoexec.bat:


//Event handlers for the button
addEventHandler OnClick 24 setChannel 1 0
addEventHandler OnClick 26 setChannel 1 1
addEventHandler OnDblClick 24 backlog setChannel 2 15; setChannel 1 1
addEventHandler OnDblClick 26 backlog setChannel 2 255; setChannel 1 1
addEventHandler OnHold 24 addChannel 2 -5 0 255
addEventHandler OnHold 26 addChannel 2 5 0 255

// this is not really tuyaMCU but we will treat it as such
startDriver TuyaMCU
// set baud rate
tuyaMcu_setBaudRate 115200

// create a toggle and a dimmer
setChannelType 1 toggle
setChannelType 2 dimmer256


// invoke refresh on change
addEventHandler OnChannelChange 1 startScript autoexec.bat refresh
addEventHandler OnChannelChange 2 startScript autoexec.bat refresh

refresh:
// channel 5 is temporary variable, from 0 to 255*3, multiplied also by toggle value
setChannel 5 $CH2*3*$CH1
// split into two bytes
setChannel 3 $CH5/256
setChannel 4 $CH5%256
// send the two bytes
tuyaMcu_sendCmd 0x30 00$CH3$$CH4$

zeronok2k · Answer

Hi. How about flashing using Tuya-Cloudcutter? Someone tried? Did it work? Thanks!!!

divadiow · Answer

Cloudcutter success will depend on the firmware version. I see no mention of the versions the device in each thread came with. Do you know your version? have you dumped the firmware?

ferbulous · Answer

Hi, how do you connect the dimmer to a momentary switch (with single pole)?
Do you mind sharing the wiring connection? I'm not quite sure how to connect the 'power' terminal next to the '-' terminal.

Also, thanks for confirming that multipress works with tuya mcu, so you just can't decouple the relay for this dimmer right?

p.kaczmarek2 · Answer

This is not a TuyaMCU device. It's using a custom protocol that has also UART packet similiar to the MCU one. Please check out the reverse-engineering topic:
https://www.elektroda.com/rtvforum/topic4039890.html
The multipress here is using standard GPIO button, not a TuyaMCU one.
You can decouple anything here. The dimmer control is done by script, here:


// send the two bytes (this is TuyaMCU command but protocol actually is a simpler one, it's not classic TuyaMCU)
tuyaMcu_sendCmd 0x30 00$CH3$$CH4$

Let me know what exactly you want to achieve and I will try to help.

ferbulous · Answer

@p.kaczmarek2 thanks, i thought all tuya dimmers use tuya mcu. I just need to figure how to wire it to momentary switch since I plan to use it for 2 way

p.kaczmarek2 · Answer

Wire it as in manual: and then set the role for appropriate OBK pin to Button, I guess...

ferbulous · Answer

@p.kaczmarek2 Yes, there’s the manual but it’s not too clear how to wire the ‘power’, ‘+’ and ‘-‘ to the 1 gang switch with only 2 terminals

p.kaczmarek2 · Answer

What do you mean by 2 terminals, can you show the photos of the device you have?

Otherwise, just wire as in manual, keep in mind that there will be 3 GPIOs of BK7231 that you can later script to do whatever you want. Those GPIOs connects to the WiFi module, not to the MCU. They are configurable in OpenBeken.

ferbulous · Answer

@p.kaczmarek2 hi, it’s this pic I posted in previous post It’s a 1 gang momentary switch with 2 terminals in the back, unless i need a different switch for the dimmer

p.kaczmarek2 · Answer

Sure, so the configuration steps are:
1. turn off the power
2. connect a momentary switch between gpio output and N, like on image:

So there will be only two wires to the switch and switch will connect them when pressed.

3. in OBK, set the Button role for the appropriate pin. You can also try using GPIO doctor if you are not sure which pin is used. But, as far as I know:

Log in, to see the code

so if "plus" pin is 26, then you can connect momentary switch as I said to 26, and it should work with Button role in obk. You can also use dInput role for debugging.

Please try the following steps and let me know if it works, if not, we'll investigate.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

Helpful post? Buy me a coffee.

ferbulous · Answer

@p.kaczmarek2
Hi, is this the correct way to wire to the switch?
It looks like I’ll need to use 3 button switch similar to other tuya dimmers for separate power, brightness up and dimming

From the diagram it looks like the neutral’s bridged to the switch?

p.kaczmarek2 · Answer

It seems ok. How your switch looks like from front? It has 3 momentary buttons? With some more scripting, it should be possible to use one button - click to turn on/off, hold to adjust brightness.

ferbulous · Answer

So I don’t think my unit working This is straight out of the box with stock firmware and wiring just neutral & live doesn’t seem to turn it on/no led I’ll have to claim for replacement

ferbulous · Answer

@p.kaczmarek2 Haven’t wired it to the switch, but it doesn’t seem to turn on at all with just Lin and Nin wired.

p.kaczmarek2 · Answer

Uh, sorry, I didn't read your message well! Now wait a minute.
It does not have a relay, so you won't hear a click.
Can you connect a classic, dimmable (a LED one won't work unless marked as dimmable) bulb to the output and try again? How does the panel look in the app?

ferbulous · Answer

@p.kaczmarek2
Doesn’t get detected by the app at all and there’s no led indicator blinking or anything.
I’ve already got the refund, so I’ll open it up anyway if and flash openbeken if it does anything.

p.kaczmarek2 · Answer

Maybe take a 2MB flash copy as well, and try to check the original Tuya bootlog. Interesting.

ferbulous · Answer

@p.kaczmarek2
Hi, looks like the dimmer boots up and connected to wifi.
Probably it was stock firmware issue?
Anyway, what do I assign for pin 24 & 26 before I use the script? Do I just set button 0 or 1 for pin 7

p.kaczmarek2 · Answer

Very good! So, if you want to script button events, the best option is to use Btn_ScriptOnly role. It's a button role that casts events but does not automatically toggle relays.

ferbulous · Answer

@p.kaczmarek2 since pin 24 & 26 are input buttons, is it possible to add rotary encoder like ky-040?

Spięcie · Answer

>>21206747 .

Warm welcome,

I am using a module to control a fan blowing heat from a fireplace with a small power of about 140W, quite nicely this solution works, but I would like to change the control range for example 70%-100%.
this minimum value of 70% will allow the fan to start and protect it from damage/overheating.

where is the code section for the adjustment range , look for it in autoexec.bat ? - thank you for your help,

kind regards

fortunatornforty76 · Answer

>>21004711 FS-02HW mini Smart switch also has CB2S Wi-Fi module with wrong silkscreen

iotflasher · Answer

p.kaczmarek2 helped with the following post:

pierdata · Answer

Hi

I think I have a newer revision of the PCB.

I'm not as knowledgeable as you. Is there no template setting for this device? I don't see a ready-made template for importing into the web app in this thread.
no need to set any GPIO via template?

now in the config I have:

Spoiler:

{
"vendor": "Tuya",
"bDetailed": "0",
"name": "Full Device Name Here",
"model": "enter short model name here",
"chip": "BK7231N",
"board": "TODO",
"flags": "267268",
"keywords": [
"TODO",
"TODO",
"TODO"
],
"pins": {},
"command": "",
"image": "https://obrazki.elektroda.pl/YOUR_IMAGE.jpg",
"wiki": "https://www.elektroda.com/rtvforum/topic_YOUR_TOPIC.html"
}

extracted from original firmware backup:

Spoiler:

{
"display_led1_pin":"8",
"lightminus_sw_lv":"0",
"is_rlen":"0",
"brightindi":"1",
"rsthold":"5",
"net_trig":"0",
"ctrl_type":"1",
"jv":"130",
"bt_lv":"0",
"standtime":"3000",
"is_swled_en":"0",
"is_netled_en":"0",
"ffc_select":"0",
"btkm":"0",
"total_stat":"0",
"mcu_type":"0",
"brightstep":"20",
"bt_pin":"7",
"baud_rate":"115200",
"module":"CBU",
"display_led1_lv":"0",
"lightminus_sw_pin":"24",
"init_conf":"100",
"onoffmode":"0",
"lightplus_sw_pin":"26",
"periodtime":"5",
"lightplus_sw_lv":"0",
"crc":"126"
}

When I run the autoexec.bat shown in this thread , it kills the device, and I no longer see it on my network, so I have to reflash it.

original firmware backup: readResult...-07-11.bin (2 MB)You must be logged in to download this attachment.

Please help.

Regards
prucho

Option	What the thread shows	Practical result
Follow PCB silkscreen	3.3V and GND can be mislabeled on FS-05R	Wrong wiring and failed flashing
Follow Tuya CB2S datasheet pinout	Repeatedly confirmed in FS-05R cases	Correct power and serial mapping
Replace with ESP-02S/TYWE2S	Physical swap blocked by layout mismatch	Poor replacement path
Use OpenBeken script	Working dimmer control shown at 115200 baud	On/off and brightness control

[BK7231N/CB2S] Inverted PCB layout of CB2S on FS-05R Mini Dimmable Switch

Why does the CB2S pinout on this FS-05R Mini Dimmable Switch look mirrored, and how should I wire or replace it?

Topic summary

FAQ

Quick Facts

Why does the CB2S silkscreen on the FS-05R mini dimmable switch appear mirrored or wrong, and how can I identify the correct pinout?

How do I verify the real 3.3V and GND pins on an FS-05R CB2S board when the PCB labels do not match the Tuya datasheet?

What is CB2S, and how is it different from CB3S or ESP-02S/TYWE2S in Tuya-based dimmer modules?

What is TuyaMCU in the context of OpenBeken, and why is the FS-05R described as using a TuyaMCU-like custom UART protocol instead of a classic TuyaMCU?

How can I flash or configure an FS-05R BK7231N/CB2S dimmer with OpenBeken when BekenWriter only shows endless 0xFF output on serial?

Which OpenBeken pin roles should I assign on the FS-05R for GPIO 7, 8, 24, and 26 to get the onboard button, LED, and dimming controls working?

How do I use autoexec.bat on OpenBeken to control the FS-05R dimmer, including on/off, dimmer256, and UART brightness commands?

What is the best way to set up single-click, double-click, and hold actions for the FS-05R buttons in OpenBeken scripts?

How should a 2-terminal momentary wall switch be wired to the FS-05R terminals labeled power, +, and -, especially for 2-way control?

What troubleshooting steps should I follow when an FS-05R dimmer powers from L and N but shows no LED, is not detected by the Tuya app, or seems dead out of the box?

How does Tuya-Cloudcutter compare with serial flashing for the FS-05R, and how much does the installed Tuya firmware version affect success?

What does Btn_ScriptOnly mean in OpenBeken, and when should it be used instead of a normal Button role on BK7231N devices?

How can I limit the FS-05R dimmer control range in OpenBeken, for example to 70%–100%, to protect a 140W fireplace fan from stalling or overheating?

What causes an OpenBeken autoexec.bat script or template import to make a newer FS-05R PCB revision disappear from the network, and which flags or pin settings should be checked first?

How could a rotary encoder like the KY-040 be integrated with an FS-05R running OpenBeken for dimming control, given that GPIO24 and GPIO26 are already used as button inputs?