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How To Unbrick ESP8266 (Blinking Blue Led)¶
I have some ESP8266 (NodeMCU DEV kit, ESP-01 and ESP07). Two of them bricked during firmware upgrade (Flashing). The first was my mistake because I mistyped the memory address, and the other was a power outage. So I had two bricked ESP. After I powered up the board, the blue led was blinking continuously and rapidly. I tried to update the firmware with custom builds and with builds from https://nodemcu-build.com/, but all my tries was unsuccessful. I was a bit upset and was thinking about getting rid of them, but I never give up anything so easily. After doing some google search I found some articles about the memory map of the ESP, and some article on "how to update boot loader". Honestly, I'm not a developer, and I couldn't say everything I read was clear to me, but finally I successfully brought two ESP back from the death. :) I'm writing this post just because I think it will be useful for someone, some time. I absolutely do not guarantee that this method will work in any cases, the only think I can suggest: do not give up trying, and googleing. :) And note that maybe your ESP has a different memory layout, so first do some search to find as many details about your ESP as you can.
1. Check your EPS8266 Symptoms¶
As I mentioned above the blue led on my esp was continuously blinking, when connected it to my computer. I used an USB to serial converter, and saw this message repeating endlessly:
ets Jan 8 2013,rst cause:2, boot mode:(3,6) load 0x40100000, len 25952, room 16 tail 0 chksum 0x9a load 0x3ffe8000, len 2276, room 8 tail 12 chksum 0x03 ho 0 tail 12 room 4 load 0x3ffe88e4, len 8, room 12 tail 8 chksum 0x3f csum 0x3f rf cal sector: 251 rf
I think this means that the ESP was restarting continuously, maybe because it couldn't find the boot loader or any of the necessary files. I could upload the firmware, so I think one of the following files must have been missing, corrupt or overwritten:
2. Collect The Necessary Files¶
If the links become broken or unavailable, you have two options: 1. Do some search (Google is your best friend. :)) 2. Compile the Nodemcu firmware (with SDK). To do this you can follow my previous post.
I don't want to write the whole process again, so after you successfully compiled NodeMCU firmware on your own, you should have the necessary files.
Actually you only have to compile "esp-open-sdk", the NodeMCU firmware isn't definitely needed to unbrick, if you have a pre-compiled firmware, you can use it. NOTE: If you use some downloaded firmware instead of compiling one, please check which SDK was used for compiling!
The files you will need can be located here:
nodemcu@openhab:~/esp-open-sdk/ESP8266_NONOS_SDK_V1.5.4_16_05_20/bin$ find . ./boot_v1.2.bin ./boot_v1.5.bin ./upgrade ./esp_init_data_default.bin ./at ./at/512+512 ./at/512+512/user1.1024.new.2.bin ./at/512+512/user2.1024.new.2.bin ./at/README.md ./at/1024+1024 ./at/1024+1024/user2.2048.new.5.bin ./at/1024+1024/user1.2048.new.5.bin ./at/noboot ./at/noboot/eagle.irom0text.bin ./at/noboot/eagle.flash.bin ./blank.bin
3. Flashing the ESP¶
Before you flash the files to the ESP, double-check the size of its flash. Based on the following tables [^1] upload the files to the appropriate memory address.
I used nodemcu-flasher to flash my ESP with these settings:
- blank.bin --> 0x7E000
- esp_init_data_default.bin --> 0x3FC000
- user1.1024.new.2.bin --> 0x01000
- boot_v1.5.bin --> 0x00000
The last step is to flash your firmware, for example with a custom build one:
nodemcu@openhab:~/nodemcu-firmware/bin$ ls -al total 444 drwxr-xr-x 2 nodemcu nodemcu 4096 Oct 24 18:26 . drwxr-xr-x 15 nodemcu nodemcu 4096 Nov 1 11:28 .. -rw-r--r-- 1 nodemcu nodemcu 28160 Nov 1 11:29 0x00000.bin -rw-r--r-- 1 nodemcu nodemcu 413495 Nov 1 11:29 0x10000.bin -rw-r--r-- 1 nodemcu nodemcu 79 Oct 24 18:20 .gitignore
I hope this post will be useful, and you will be able to unbrick your ESPs.
- https://nodemcu.readthedocs.io/en/master/en/flash/ (Upgrading Firmware)