I can't flash my ESP8266 (ESP-01). I have 3.3 V and ground connected, Rx to Tx and Tx to Rx on my USB to serial adapter. I also have GPIO0 connected to ground too.

I am using an external power supply but the USB adapter and power adapter share a common ground.

I'm using a Mac and ESP tools to flash it, and it has worked before.

The command I am using is:

sudo ./esptool.py --port /dev/tty.wchusbserial1410 write_flash 0x00000 AT22SDK10020150320boot12.bin

But the response is:

A fatal error occurred: Failed to connect to ESP8266

This make me think something is wrong with receiving data from the ESP because when attempting to connect, the ESP's blue LED flashes.

My USB to serial adapter works fine though as I've tested it with my Arduino.

  • CH_PD must also be connected to 3.3v Jun 9, 2016 at 3:12
  • If you've got led flashes and signs of activity and such a non-descriptive error, just try disconnecting / reconnecting and try again (if you havent already)
    – 8eecf0d2
    Jun 10, 2016 at 8:54
  • Did you ever find a solution to this?
    – mh00h
    Oct 20, 2016 at 8:33
  • @mh00h yes, I just bought a new one. Wasn't worth spending time on when they're as cheap as they are.
    – Blease
    Oct 25, 2016 at 10:46


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