I'm managing to upload a sketch to the ESP8266 01. I have been researching on internet but I'm not able to get it.

I have installed the libraries for Arduino IDE and my circuit is the ESP powered by 9V converted to 3.3V using a LD 3.3 converter. I tested the voltages and works fine. Also the led in ESP is on (red). To connect to the computer I'm using a TTL USB cable without vcc connected only for tx and rx.

The commands for the ESP works fine (AT commands), but when I try to upload a sketch it shown the following error:

espcomm_open failed

I also have connected to GP0 (ESP) a button to ground. The circuit is:

9V battery --> 3.3V converter --> ESP---> TTL

Anyone knows about that error and why could be? Because the AT commands works fine. Maybe I need to provide more information but not sure.

My goal is to do this tutorial: https://learn.adafruit.com/downloads/pdf/esp8266-temperature-slash-humidity-webserver.pdf

Another problem that I have following that tutorial is that in Arduino IDE, I cannot setup esptool as programmer, because isn't there. I loaded the same library for esp

  • If when I tried to do the commands and now doesn't work, means that I have to reflash the AT firmware again?
    – CapAm
    Nov 11, 2015 at 15:17
  • Are you using the original AT firmware?
    – Ikbel
    Nov 13, 2015 at 18:01
  • Are you releasing GP0 from ground once the ESP has turned on? Dec 26, 2015 at 0:56

1 Answer 1


Following on from user1637451 the following sequence has always worked for me:

  1. Before download, pull both GPIO0 and RST to ground.
  2. Release the pull down on RST, but keep GPIO0 low.
  3. When the IDE has finished downloading, release GPIO0 from low.

I usually have pull-up resistors (10K) on both RST and GPIO0.

As to the IDE problem. I used the tutorial from Sparkfun entitled "ESP8266 Thing Hookup Guide" and then the section "Installing the ESP8266 Arduino Addon". Because I used a different ESP8266 board to them I set the IDE to use the "generic ESP8266 board". This worked for me.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.