Flashing yet another Mini Smart Switch with a T34, aka BK7231N chip

Question

This is for another Mini Smart Switch,
this time with a T34 AKA BK7231N

I did not read this forum thus I did not know about Tuya-Cloudcutter and thus flashed it the difficult way.
Please try Tuya-Cloudcutter first!!

The LED is on 6
The Switch input is on 14
The Relay is on 15
The Button on 24

Log in, to see the code

sp4rk1e · Accepted Answer

bought some of these so called 'Mini Smart Switches' from our favorite Chinese marketplace, For incredible 2.59€ per piece.

again a new variant of this device. At least I've not seen such on this forum.

Unfortunately with a T34 directly mounted on the board. Even with all of our beloved flash signals exposed somewhere on the board.

Except TX. Holy crap no way to grab this pin except removing the whole chip :-(

for easier future use I handcrafted a small T34 flash adapter for my favorite USB ESP32 in circuit flash tool:

my working OBK config is like this:


{
  "vendor": "Tuya",
  "bDetailed": "0",
  "name": "Full Device Name Here",
  "model": "enter short model name here",
  "chip": "BK7231N",
  "board": "TODO",
  "flags": "64",
  "keywords": [
    "TODO",
    "TODO",
    "TODO"
  ],
  "pins": {
    "8": "WifiLED;0",
    "10": "TglChanOnTgl;1",
    "23": "Btn;1",
    "26": "Rel;1"
  },
  "command": "powersave 1",
  "image": "https://obrazki.elektroda.pl/1476559000_1759204894.jpg",
  "wiki": "https://www.elektroda.com/rtvforum/viewtopic.php?p=21705064#21705064"
}

p.kaczmarek2 · Answer

Thanks for sharing! Your template is now live on our devices list:

See: https://openbekeniot.github.io/webapp/devicesList.html

Good job with flashing it. Nice way of repurposing unused button pads. I hope it won't be too hard for other our readers as well. I'm worried to see more and more T34 devices around, Hopefully they won't totally replace easily-flashable CB2S/CB3S/etc modules.

Added after 25 [seconds]:

PS: Consider enabling powersave on this board or you may need to do this fix later:
https://www.elektroda.com/rtvforum/topic3898805.html

djramu · Answer

Hello.
I have a problem.

I tried Tuya CloudCutter but couldn't manage. I think I prefer flashing via uart. With the GUI Flash Tool, can I change the firmware of this device? I tried to find the RX and TX pins but no success. Are You able to tell how You managed to flash this chip via uart?

p.kaczmarek2 · Answer

Do you have the exactly the same version as in the first post? It is possible to flash it with GUI Flash Tool, but you need to access UART pins.

djramu · Answer

It goes like this. I would like to use uart but after soldering in the theoretical uart pins i don't have communication. I tried with the pins marked in red.

p.kaczmarek2 · Answer

This is the good approach. It's easy to tear off the QFN pad when using too large or not fixed in place wires.

p.kaczmarek2 · Answer

I got the same as @sp4rk1e Code: JSONLog in, to see the code Added after 1 [minutes]:

sp4rk1e · Answer

if everything else fails this board is a nice 3.3V power supply for other ESP32 projects after removing unnecessary parts. Of course setup must be completely isolated. At least I haven't seen a DIY power supply for the mains at that size yet.

p.kaczmarek2 · Answer

It wasn't that bad: but I probably should buy this:

woessner · Answer

I bought six of them because it was quite easy to flash them last time but now I had the chips where the pins could not be accessed from the side :-(

Hand-soldering tiny wires to the chip was a nightmare, though, but I did that on one of them and successfully flashed the firmware.
Doing that on the five remaining ones --> no way!
Thus I printed a jig to hold the chip.
That worked amazingly!
Thus I have to share the CAD files for that.

PS: The LED is on 8
Button on 10
and Relay on 26
Please find attached STL and Inventor files. If you need a different CAD file format, just send me a PM.

p.kaczmarek2 · Answer

Interesting, I didn't think about such approach. CAD files could be useful, zip them and attach, or I can help if it's not working for you. Nice design.

woessner · Answer

>>21732366 Zip files worked!The print is accurate enough to give a good alignment, and on some of them I had to press down a bit on the 3D print to get a good contact with the needle tips, but other than that, no problem.I did add a bit of leaded solder on the chip pads before putting them in the jig; that might have helped a bit with the contact too, and I had to do that anyway to reflow them after programming.

Flashing yet another Mini Smart Switch with a T34, aka BK7231N chip

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