I am trying to recover, self died sensors.
5-4 years ago I bought 4 of them on aliexpress for like 25-30euro for 1pcs. At that time it was quite expensive, nowadays you can get such sensor for like 8-10 euro. All 4 sensors died when the battery voltage was slowly decreasing. Sensor were set to report the data every 20minutes, they were used to control heating in house. The battery set could withstand like 8-10 weeks. If you did not change them on time the sensor was "kaput". So is the story. The problem was reported by other users wide on internet. The reason is probably explained in the errata of the MindMotion MM32F003 mcu. As for now I just want to repair them, "as it is"(actually as it was).
The issue: the device is losing wifi connection, the LCD display works, temp humidity measurements works, you can press the pair button, wifi icon is blinking - but it does not connect to the router. After battery insertion it starts, but id does not set proper time wihout network acces, clock starts and counts from 0:00.
I figure out that the problem is in the WiFi CSB3 module.
What I did I cloned the data from other newest similar sensor //but different MCU// with CB3S module, and I could pair it. I can connect it to network and the sensor is visible in the tuya Smart app. The donner device despite is powered went offline. I observed that they were visible kind of alternatelly. When one is visible the other is offline. This is I guess due to cloning of the wifi data, I do no tknow perhaps MAC or other ID.
I can dump all the broken CB3S modules. The tricky point is I that..guess some section should be uniqe like MAC or tuya IS or key.
As far as I remeber the broken//erased CB3S module was RF active, however, on a different way than good module. I was observing the RF activity on spectrum analyzer.
I will compare the dumps which are on the second computer. Tomorrow.
There are some bytes differences in good and corupted CB3S module:
