ESP8266 Community Forum

Used hardware: Adafruit HUZZAH ESP8266
Used software:

- Arduino IDE V1.6.7 with esp8266 board V2.0.0
- AT firmware (latest from github https://github.com/espressif/ESP8266_AT)
- NodeMCU (0.9.6-dev_20150704 from github https://github.com/nodemcu/nodemcu-firmware/releases

Used flash tools:

Espressif ESP FLASH DOWNLOAD TOOL V2.4
esptool.py

What happened:

- Tested my own project (written with Arduino IDE)
- Used Arduino OTA (device is in difficult accessible location)
- OTA worked several times
- OTA failed, device not connecting to WiFi anymore, even after power off/on cycle
- Removed ESP module, try to reflash over serial port with FDDI cable
- Still ESP module fail to boot

Found error codes:
On serial monitor (74880 baud) module shows always endless loop of

Trial to recover:
a) Reflash module with working code (works on different ESP12 module). ==> fail, same error, only epc1=0x... shows different address
Terminal output:

b) Reflash module with NodeMCU 0.9.6 ==> fail, same error, only epc1=0x... shows different address

c) Reflash module with lates AT firmware found on github => fail, same error, only epc1=0x... shows different address

d) Erase complete flash with esptool.py. Reflash module with boot and esp_init_data_default.bin from latest AT firmware (no user1.bin or user2.bin was flashed) ==> no more Fatal Exception

Try to eliminate power supply problem
Tried 4 different power supplies (Adafruit Huzzah ESP8266 has onboard power regulator, input voltage range 3.3V to 16V) and 3 different Adafruit Huzzah ESP8266 modules

5V USB supply from iPhone, 5V, 1A
5V USB supply from Samsung Note 10.1, 5V, 2A
9V wall plug with additional caps (470uF elec. & 100nF ceramic), 9V 1A
5V from LM317 build power supply, 5V 1.5A

=> all the 4 power supplies work fine on the 2 ESP modules without problem
Try to check for flash failure
a) Erase and read back

- erase complete flash with esptool.py erase_flash
- read back complete flash with esptool.py read_flash 0 4194304 erased.bin
- check erased.bin with hex editor ==> complete content is 0xFF

b) Flash and read back

- erase complete flash with esptool.py erase_flash
- flash AT firmware with ESP FLASH DOWNLOAD TOOL V2.4
- used addresses:

• 0x000000 boot_v1.1.bin
• 0x001000 user1.bin
• 0x07c000 esp_init_data_default.bin
• 0x3fc000 esp_init_data_default.bin
• 0x07e000 blank.bin
• 0x3fe000 blank.bin
  - use CombineBin to create combined file target.bin
  - read back complete flash with esptool.py read_flash 0 4194304 at.bin
  - compare at.bin with target.bin ==> complete content is identical

==> seems the flash is working fine

I went to a lot of forums and searched for this problem, but found no recovery solution that worked in my case.
Anybody has an idea what else I can try to recover the module?

Hi!

I am experiencing the same issue, were you able to solve it? Thanks!

Best regards,

ayx00 wrote:Hi!

I am experiencing the same issue, were you able to solve it? Thanks!

Best regards,

Nope, the module was broken. I talked to Espressif directly. They wanted me to send the module for investigations which would cost me more than just buying a new one.
So my solution was to get a new module instead.

It was never clear what was broken in the module.

Hi there,

I've the same issue. It looks like the Fatal exception error is happening only when user1.bin code is being executed. There may be something wrong with one of the eFuses perhaps?
Thanks.