ESP8266 Community Forum

- Mon Jan 05, 2015 9:06 am #6339 After 1 month of rigorous developing on my ESP-07 module which involves about average 40-60 times reflashing, my module finally refuses to boot.
The phenomenal is gradually worsening, from at the beginning it fails to boot occupationally, to a prolonged period that it refuses to boot continuously but once booted, it is all right for the whole day even between power cycling, until today it enters a wdt reset loop for an hour, then completely refuses to boot.
All I have now it boot message as

Code: Select all 
 ets Jan  8 2013,rst cause:1, boot mode:(3,7)

load 0x40100000, len 29288, room 16
tail 8
chksum 0x49
load 0x3ffe8000, len 1972, room 0
tail 4
chksum 0x26
load 0x3ffe87c0, len 7364, room 4
tail 0
chksum 0xb3
csum 0xb3


The module draws 200mA at this stage.

I wonder if anyone has observed the same phenomenon. I have ruled out firmware issue since I have tried many versions of firmware all have the same result. I guess the flash chip died (but it writes successfully). Maybe I'll popup the metal can and replace the chip to verify.

My ESP8266 dev board https://www.tindie.com/products/Ba0sh1/ ... d-adapter/

- Mon Jan 05, 2015 10:19 am #6350 Reply to my own topic:

I replace the flash chip from another failed (burnt) module and it all works again!

I put the defunct flash chip into a programmer, erase the chip and do a blank check, it fails.

For information the chip is GD25Q40BT by GigaDevice, datasheet here: http://www.gigadevice.com/product/download/119.html
It is marked as EOL in the product line but my particular chip date code is 1435 (fishy?) Anyway the chip is spec'd at 100000 cycles any I am no where near it.

Just for information sharing.

My ESP8266 dev board https://www.tindie.com/products/Ba0sh1/ ... d-adapter/

- Mon Jan 05, 2015 10:51 am #6354 Maybe the are using scrap chips that failed the end-of-line tests.
Wouldn't be the first time.

- Mon Jan 05, 2015 1:50 pm #6377 Hmm, maybe this sort of thing is the reason that these things are so cheap!

Either failures or grey-shift type operations perhaps?

What does that date code suggest to you? Why do you say fishy from that?

And does anyone know of higher grade modules which can be expected to last for years?

Worth the extra few pence surely?