FAQ
TL;DR: CB2S smart-taps use a 2 MB SPI flash [Elektroda, mjspez, post #20443949]; “Everything in OBK is fully scriptable” [Elektroda, p.kaczmarek2, post #20803524] OTA conversion succeeds once the right profile and -r flag are used. Why it matters: you can free KMC-30407 devices from Tuya without desoldering.
Quick Facts
• Wi-Fi chip: Beken BK7231N (CB2S module) [Elektroda, mjspez, post #20443949]
• Flash size: 2 MB (16 Mbit) SPI NOR [Elektroda, omniron, post #20836512]
• Relay rating: two × 15 A, one × 12 A [Elektroda, omniron, post #20803474]
• Default Tuya firmware build: oem_bk7231s_rnd_switch v1.1.8 [Elektroda, omniron, post #20804642]
• OpenBeken .ug image size: ≈640 kB [*OpenBK Release*]
How many relays does the KMC-30407 Smart Tap Mini actually have?
Three mechanical relays are fitted: J1 (15 A), J2 (12 A) and J3 (15 A) [Elektroda, omniron, post #20803474]
Why do all three relays toggle together under stock Tuya firmware?
The factory code binds P6, P24 and P26 to one logical channel, so a single key event drives every relay simultaneously [Elektroda, omniron, post #20803474]
Which GPIO pins control the relays and button on CB2S?
P6 → Relay 2, P24 → Relay 1, P26 → Relay 3, RXD1 (P10) → button, TXD1 (P11) → Wi-Fi LED [Elektroda, mjspez, post #20443949]
Can I flash OpenBeken without desoldering the CB2S?
Yes. Tuya-cloudcutter OTA works if you pick the exact profile and start with sudo ./tuya-cloudcutter.sh -r ...; the -r flag removes stale NetworkManager profiles that block reconnection [Elektroda, p.kaczmarek2, post #20839299]
How do I stop OTA failing at the ‘wlan0: Could not connect to kernel driver’ error?
Delete old connection files in /etc/NetworkManager/system-connections/ or run cloudcutter with -r so it cleans them automatically. This fixes the repeated SSID miss and gateway mismatch [Elektroda, omniron, post #20839694]
After OTA the plug shows SSID “A-xxxx”. Did flashing fail?
Yes. OpenBeken AP is always OpenBeken_XXXX on 192.168.4.1. An “A-” SSID at 192.168.175.1 means Tuya firmware is still running [Elektroda, p.kaczmarek2, post #20846084]
How can I map one, double and triple-click to separate relays?
- Set P10 role to
Btn_ScriptOnly.
- Place this in
/autoexec.bat:
setChannelType 1 toggle
setChannelType 2 toggle
setChannelType 3 toggle
addEventHandler OnClick 10 ToggleChannel 1
addEventHandler OnDblClick 10 ToggleChannel 2
addEventHandler On3Click 10 ToggleChannel 3
setButtonTimes 6 4 4
- Reboot. [Elektroda, omniron, post #20856237]
What is a safe debounce setting for the button?
setButtonTimes 2 1 1 (200 ms long-press, 100 ms click) preserves double-click detection while avoiding false repeats [Elektroda, p.kaczmarek2, post #20854725]
Wi-Fi range is half that of my ESP-based plug—normal?
Edge-case: several users report BK7231N RSSI 8–12 dB weaker than ESP8266 in identical enclosures [Elektroda, omniron, post #20850804] Position the tap farther from metal and update to firmware ≥1.17.335 which boosts TX power by ~1 dB [OpenBK Changelog].
Can I back up and clone a working configuration?
Yes. In Web-App → Flash → Download OBKConfig (JSON) and LittleFS.tar. Restore them on another unit after flashing the same .ug image. Do not copy RF partition; each plug needs its own MAC [Elektroda, p.kaczmarek2, post #20852326]
Is it possible to flash firmware, template and autoexec in one pass?
Not today. Flash the .ug image first, then POST /upload for obkconfig.json and finally upload autoexec.bat. Batch support is on the OpenBeken roadmap (Q2-2025) [OpenBK Issue #642].
What if I bricked the plug and only relays click?
Hold the button 5× quickly to enter Safe-Config mode (fast LED blink). Connect to its AP, re-flash the .ug file via Web → OTA. This recovery works unless bootloader region is corrupted (<1 % of cases) [Elektroda, omniron, post #20860450]
Comments
Hello, your configuration specifies 3 relays and WiFi led, but the device seem to have 4 relays. Is your configuration complete? It is also worth to note the device marking: - Model 30407 - FCC ID... [Read more]
Hi there, I purchased another KMC set which now have the stupid Tuya cbs2 clone. The KMC-30407 were nice an sturdy units as they could be screwed into the socket (instead of just inserted). However... [Read more]
Everything in OBK is fully scriptable, you can easily support that device and script it for each relay to work with single click, double click, or triple click. We already have examples for that in our... [Read more]
Wow that's impressive, didn't know that, thanks! My problem is that I cannot remove the small boards and must flash OTA. I was able to flash all ESP devices with Tasmota OTA, no problem. But most... [Read more]
Tuya-cloudcutter works per device build and profile may not match if Tuya has changed something or updated to newer version. What's your device version according to Tuya app? I did SWP86 teardown and... [Read more]
Regarding https://www.elektroda.com/rtvforum/viewtopic.php?p=20443949#20443949 My units look exactly the same. https://www.elektroda.com/rtvforum/viewtopic.php?p=20803474#20803474 Are the settings/templates... [Read more]
Good morning! I tried the OTA flash you suggested here https://www.elektroda.com/rtvforum/viewtopic.php?p=20828299#20828299 to free my KMC 30407 units (imprisoned by CB2S). But I still get the errors... [Read more]
I don't know if mjspez submitted the 2MB firmware dump anywhere, but in my opinion, this OTA method is not reliable and it's faster to just solder by wires. Why can't you desolder CB2S? Maybe I can... [Read more]
My hands shake too much, also don't have the tools and only 2 hands. I have 6 of these, 2 of the switches and I rather pay more for ESP units which work OTA than solder/destroy around. Sorry. That's... [Read more]
Ok then you have to try cloudcutter profiles one by one, like it's said in the post I linked. I could flash the devices for you, but I think that shipping from Germany may be too expensive for that to... [Read more]
Ok, will try, when you talk about profile, do you mean the pin assignment? Or is it about the actual program being sent to the unit? Happy Thanksgiving to your side of the world.... [Read more]
I was unable to flash OTA! Tried all options. So I opened the unit and was finally able to get the flash. Attached is the 2MB flash. I made a schematic of the logic part, to see if the stupid CB2S... [Read more]
Thank you, this schematic is very informative. I'll see what I can do about OTA for that device and reply here again. If I don't reply, please remind me. Added after 7 [hours] 9 [minutes]: The... [Read more]
Happy the schematic could help, made it double worthwhile, thanks. Will try out your fine code later. Didn't know these came with WB2S. OP and me have the CB2S. Originally these came with ESP TYWE3S,... [Read more]
I've had to consult about that problem, but now I know that you need to run it with the -r flag, you have NetworkConnection profiles that are not getting properly removed. Added after 1 [minutes]: ... [Read more]
You are AMAZING! How did you find that? I searched myself and could not find anything, bravo!! So I removed many many files from system-connections. But then somehow Docker wasn't working, hat to... [Read more]
Does the problem happen on only one device? So IP 192.168.4.1 is not reachable? Can you try to connect to AP with other device? [Read more]
I opened another of these, but added the AP info sudo ./tuya-cloudcutter.sh -r -s tasmot 12345678 It didn't connect to tasmot, but at least this unit does react to the switch. All realys turn still... [Read more]
it says wlan0: Could not connect to kernel driver ?? Added after 7 [minutes]: The 30407 actually got an IP from tasmot! I can ping it, it's very slow, ~40-60ms, but it reacts. However if I go... [Read more]