This was my first time flashing directly on board. I tried to flash a Water Sound v3 https://nl.aliexpress.com/item/1005007625016049.html , which I could not find on the forum but is a water detector with a CBU-NL board.
I understood CBU-NL always has a BK7231N.
I used a USB-to-serial and connected everything like described on the "[BK7231N/CBU] Door sensor without TuyaMCU - easy flashing and configuration guide", https://www.elektroda.com/rtvforum/topic3994294.html and checked if anything was accidentally shorted.
CBU-NL Pin 13 GND connected to USB-to-serial GND
CBU-NL Pin 14 3.3 V connected to USB-to-serial 3.3 V
CBU-NL Pin 15 P11 TX1 connected to USB-to-serial RX
CBU-NL Pin 16 P10 RX1 connected to USB-to-serial TX
CBU-NL Pin 18 CEN, shortly shorted to GND to start flashing
I used BK7231GUIFlashTool-build-215 with the default settings and firmware OpenBK7231N_QIO_1.18.247.bin and pressed Backup and flash new and follow the steps described in the guide (Write success!). I did not use the OBK config yet.
Config was extracted successfully from the Tuya binary and the BK7231N Decryption also seems to work (it gets bootloader, app, download).
After rebooting, LED1 kept blinking, but it did not connect to my network; I did not see an access point, and the button did nothing.
I tried flashing again with OBK config preset. The LED did not blink anymore. Neither did it connect to my network; I did not see an access point, and the button did nothing.
I tried shorting CEN and then it slowly blinks 2 times and gives 3 short blinks, after that 1 slow blink, 3 short blinks, which repeats.
Because that didn't work, I tried flashing the backup readResult_BK7231N_QIO_2026-16-1-15-08-19.bin back to the device.
The flash seems successful (Write success!). But the reboot does nothing. It did not connect to my network, I did not see an access point, and the button did nothing.
I can still flash it back and forth, but nothing seems to get the device going.
Does anyone have any ideas on what to try next to get it going again?
Edit: Typos, order of text.
