D1 mini V2.1.0 solid blue light



  • I am new to the WEMOS board have been using Particle Photons for the most part in my development and a friend from work gave me a WEMOS D1 mini now i am hooked on using them.

    All has been going well until this morning I unplugged my WEMOS d1 mini to relocate it and when i plugged it back in I am now seeing a solid blue light on the on board LED. I am able to connect and communicate with the board through the Arduino IDE and have attempted to re-flash it with my code but still the blue light condition persists. The issue seems to be with the Wi-Fi connection from the board as I load a simple sketch just to connect it to my network and it will not.

    Any help in providing what would case the solid blue light would be much appreciated.



  • The blue LED is connected to the GPIO2 pin (labeled as D4 on the D1 Mini), and is on when that pin is low. Does your firmware set that pin?



  • Thanks for the reply...my code is only initializing the wifi connection and is not triggering any LED.

    I do notice when i send output to the console it is a continuous stream of garbled data.

    I am thinking this WEMOS is destined for the trash.



  • I wouldn't throw it away just yet. The GPIO2 is also used as the TX pin of the second UART, which is used on boot to mirror the first UART and spew the diagnostics data. Since you see a continuous stream of that, it probably means that your ESP8266 got into a boot loop -- that is, it tries to boot its firmware, but then it instantly crashes, and the processor restarts and tries to boot again. One possible reason for that happening is invalid data stored in the small memory that ESP8266 has reserved for storing things like its last restart reason or the name of the WiFi network to connect to. It is possible that this area of memory got corrupted either by noise on the power line of the chip, by shutting the power off at a wrong moment when that memory was being written to, or by some code that got executed on it and wrote its data in the wrong place. Whatever the reason, this can be easily fixed by erasing the whole flash of the module or flashing a blank.bin file to it, and then re-flashing whatever program you want to run on it.



  • Thank you deshipu...
    That was exactly it i had to erase my flash memory using the following command:
    python esptool.py -p [port] erase_flash
    From my mac terminal and that cleared up the issue...

    Much appreciated.



  • @deshipu

    That's pretty smart diagnosing on your part. I wasn't aware of the GPIO2/UART connection and would not have thought of this. Thanks for adding another trick to my repertoire.


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