What hardware sits inside the Mini Smart Switch discussed in the thread?
The board carries a Tuya CB2S module based on a BK7231N SoC, an AMS1117-3.3 V LDO, a 10 A relay and cheap 400 V electrolytic capacitors [Elektroda, jkwim, post #20359513]
Mini Smart Switch - CB2S BK7231N Based
There has been many versions of Mini Smart Switch.
1. Aubess 2gang Mini Smart Switch BK7231N /CB2S
2. mini smart switch - Belon BL2028N-
3. ZN268131 WB2S BK7231T WiFi Smart Switch that allows you to connect a bistable button
4. Cheapest Wi-Fi Switch You Can Buy For Your Smart Home
I came across another product which has diferrent internals but with CB2S/BK7321N.
Software version was V1.3.8
I tried tuya-cloudcutter with many different profiles for BK7321N but was not successful.
Manual Flashing was the only way forward.
1. Opening the device was very easy. I used several guitar picks to release the tabs on the four corners.
2. There were two daughter boards with CB2S module connected to a shorter daughter board (very similar to attaching the WB2S module in link 3 above)
3. Instead of soldering wires I have decided to try out a different method to secure jumper wires to the soldering pads mechanically using custom made clips like these
I made these by removing the pins from a female header connector and then crimping the fork like metal pin to a female jumper wire connector as shown.
4. Plan of the connections
5. Since the CB2S module has pins on both sides which are arranged as alternate slots, my attachments can be secured so that only one side is touching a pin. However one has to be careful not to let the pin touch adjacent solder pads on either side.
The leftmost pin touches the solder pad on the top side of the PCB while the rightmost 4 pins touches TX1, RX1, GND and 3V3 solder pads on the bottom side.
BTW, the TX1, RX1 pins have no connections to the daughter board. So no worry about removing the CB2S module for flashing.
6. Used python uartprogram for flashing
During dumping the existing firmware use of default high speed baudrate was successful. I used option to lower the baudrate to a very very low value and it was successful but took a way long time.
Flashing new firmware at default baudrate was successful.
1. Aubess 2gang Mini Smart Switch BK7231N /CB2S
2. mini smart switch - Belon BL2028N-
3. ZN268131 WB2S BK7231T WiFi Smart Switch that allows you to connect a bistable button
4. Cheapest Wi-Fi Switch You Can Buy For Your Smart Home
I came across another product which has diferrent internals but with CB2S/BK7321N.
Software version was V1.3.8
I tried tuya-cloudcutter with many different profiles for BK7321N but was not successful.
Manual Flashing was the only way forward.
1. Opening the device was very easy. I used several guitar picks to release the tabs on the four corners.
2. There were two daughter boards with CB2S module connected to a shorter daughter board (very similar to attaching the WB2S module in link 3 above)
3. Instead of soldering wires I have decided to try out a different method to secure jumper wires to the soldering pads mechanically using custom made clips like these
I made these by removing the pins from a female header connector and then crimping the fork like metal pin to a female jumper wire connector as shown.
4. Plan of the connections
5. Since the CB2S module has pins on both sides which are arranged as alternate slots, my attachments can be secured so that only one side is touching a pin. However one has to be careful not to let the pin touch adjacent solder pads on either side.
The leftmost pin touches the solder pad on the top side of the PCB while the rightmost 4 pins touches TX1, RX1, GND and 3V3 solder pads on the bottom side.
BTW, the TX1, RX1 pins have no connections to the daughter board. So no worry about removing the CB2S module for flashing.
6. Used python uartprogram for flashing
During dumping the existing firmware use of default high speed baudrate was successful. I used
-b 9600Flashing new firmware at default baudrate was successful.
Comments
Very good presentation, but it's important to add one more note here. Those cheapest box switches have a very weak power supplies with low quality electrolytic capacitors. I even covered replacement of... [Read more]
I've a similar mini switch with CB2S but not a riser/daughterboard. I've confirmed continuity between usb-serial pins and the end of my pogo pins, and the unit is powering so ground and vcc are fine. I... [Read more]
COM port should never drop, how do you power that? COM may drop if there is a large capacitance on the device and you power it via 5V to the 3.3V LDO on the device board, that's why I usually just desolder... [Read more]
hello! thanks for replying so quickly. it's just 3.3v from the usb-serial adaptor, not via 5v or anything. I was trying to avoid desoldering because I'm not convinced I'll get it back in again! it's... [Read more]
Have you watched our tutorials? https://www.youtube.com/@elektrodacom It's been stated many times that USB to UART adapter will not provide enough current and it's recommended to use external one. Or... [Read more]
I've seen a few vids now yes, and I do recall that being stated. I need more equipment! I was just hopeful that if the device is powering and I can pair with Tuya that that would be enough current to flash.... [Read more]
Maybe that's not needed. Is there an AMS1117-3.3V visible on your board? It is possible to connect 5V from USB to the input of that AMS1117-3.3V LDO and reset via disconnecting that 5V connection. [Read more]
Yes, there is an AMS and a BP https://obrazki.elektroda.pl/3648623300_1702122320_thumb.jpg https://obrazki.elektroda.pl/9684293800_1702122388_thumb.jpg [Read more]
Here is AMS pinout: https://obrazki.elektroda.pl/3579045800_1702123396_thumb.jpg You can flash your device by soldering GND, 5V from USB, RX and TX . Then you power off/on by disconnecting 5V. [Read more]
thank you. I got this yesterday so could have a separate 3.3v and some more male-female wires (and a 10k resistor for BL602 in the future). Yes my external 3.3 and usb-ttl are connected for common ground.... [Read more]
Unsoldering WiFi board is a very reliable method and it's more easier than it seems. Just make sure to use some flux and solder wick. [Read more]
woohoo. finally did it. it was actually the RX in the end. unsoldered it with wick and flux and it flashed straight away to OpenBeken. { "nc_tp":"1", "ssid":"null", "passwd":"null", "md":"0", "random":"0", "wfb64":"1", "stat":"0", "token":"null", "region":"null", "reg_key":"null", "dns_prio":"0... [Read more]