ESP8266 Community Forum

Hello there!
I'm new to the ESP scene but familiar with Arduino and AtMega µCs.

I wanted to phase out my arduino nanos for more modern stuffs, and the ESP8266 seems a good fit. So installed the boards definitions for the Arduino IDE in order to play with it, and could blink LEDs on various GPIOs, but i got into problems when i tried to use pushbuttons.

So i defined D2 as an INPUT_PULLUP, and thus tied it to the ground using a solid core wire in order to register a "push" on my button. However, once i did that, i could no longer flash anything to the chip.

The board i use is a NODEMCU board with µUSB and USB to serial converter. I've been able to flash things to the ESP without problems, until i did what i described earlier.

I had similar problems with 2 other boards, trying to do the same thing, but by then i did not understand why the board stopped working properly.

It still shows as a COM port in the Arduino IDE, but it fails to flash, returning the following error message :
warning: espcomm_send_command: didn't receive command response
warning: espcomm_send_command(FLASH_DOWNLOAD_BEGIN) failed
error: espcomm_upload_mem failed
error: espcomm_upload_mem failed

So now, i'm stuck with 3 ESP8266 that i can't flash, and i don't know what to do, nor what i did wrong.

Did i use a forbidden GPIO? can't i use INPUT_PULLUPs on the ESP? do i need an external pullup for my button?

Now, i'm really confused, and i'm not sure to understand what GPIOs i can safely use, nor how i bricked those units...

Any help would be apreciated

wiki/doku.php?id=esp8266_gpio_pin_allocations

In brief : GPIO15 need to be pulled-down, while GPIO2/GPIO0 need to be pulled-up for normal operation (GPIO0 grounded for upload)

if it was the pin marked D2 on the nodemcu board it is gpio4 which should be safe to be in whatever state during reset/power-up. Tying a pin - which could be configured as output - "hard" to V+ or gnd is never a good idea.

If you remove all "external" components from the nodemcu and connect it to USB, what happens?
Is ist recognized?
Does the LED on the sub-pcb (ESP-12) light up?
If the terminal window in Arduino-IDE is open and baud at 74880, do you see legible messages after pushing reset button?

P.S.: there was some post mentioning that internal pullups on gpio4/5 won't work; don't know if this is true.

Hello!
Basically, what i had was the same when removing all externall stuff.
I got around it, and de-bricked my ESPs by holding the flash button, plugging it in then flashing something.
After that it responds normally and can be flashed.
However, i still don't understand well why it wouldn't work.

The internal pullup on some pins beeing defective is an interesting lead, however, if so, i guess i would have fried the chip?

What bugs me is that the ESP would not flash, as if by tying a pin to ground i had put it in some weird mode...

So i'm not left wondering what pins are safe to use on a NodeMCU module?