Now I found a lot of module stuck in fatal exception (3) as shown below. fatal exception.jpg I observe that the module crash after boot the main app code from flash memory. Compare with the good one in img_2, I curious that what the bootloader actually does in the red circle ? boot_log_good.png

Now, I found a way to make this problem happen. I curious about "make first break last" when uploading firmware to my board. So I do an experiment by holding plug in 3.3V to my board and plug in/out GND repeatedly and see boot message. I've been doing this for a while and finally ESP8266 begin to st...

I found my esp8266 stuck in fatal exception (3) and below is the log message when in the boot process. (Baud rate = 74880)

It looks like the MCU can't run my code. It happened unexpectedly despite previously being able to function normally.