Introduction: ESP-12E (ESP8266) With Arduino Uno: Getting Connected

Picture of ESP-12E (ESP8266) With Arduino Uno: Getting Connected


This tutorial is the first of three parts meant for people who want to connect their ESP8266 through an Arduino UNO board. More specifically, I will be using the ESP-12E version of these wifi modules.

I personally had a lot of trouble when I started exploring ESP8266 boards. There is a lot of information out there but parsing through it is quite daunting for a beginner and I never found a tutorial to my liking on how to use them with Arduino Uno. I therefore decided to create my own tutorial with the knowledge I gathered from endless hours of looking on sites, blogs, forums, etc. so others don't have to go through the same tedious process.

Here's what the different parts will cover:

  1. How to connect the ESP-12E to the UNO for basic operation and serial communication;
  2. How to flash new firmware to the module;
  3. How to upload your own sketches to your ESP-12E.

I'm assuming you already have some sort of breakout board for your module or a way to attach wires to the different pins. This series of tutorials will not cover how to build a breakout board. ankitdaf has a good tutorial on this subject HERE -- I'm using something very similar to his build.

I'm also not going to cover installing the Arduino IDE since you probably have it installed if you have an UNO. Here's the official link in case you don't have it.

Let me tell you from the start, THIS CONFIGURATION WORKS! I have used it successfully for a while now and it hasn't let me down (no resets or anything).

What you'll need:

  • Arduino UNO board
  • ESP-12E module (have not tested this on other versions but it might work, give it a try)
  • 3.3V power source, don't use Arduino 3.3V pin
    • I'm using a 5V USB phone charger and a step-down voltage converter
    • use something that's capable of providing at least 500mA just to be sure as some people have been noticing spikes of up to 420mA in ESP modules
    • EDIT: I'm actually using mine just under 3.6V and it seems to perform better than it did at 3.3V.
  • jumper wires
  • 4 x 10kΩ resistors
  • a breadboard
  • 2 push buttons (optional but recommended for ease of use)
  • a 470uF capacitor (optional but recommended for stability)

Step 1: Make the Connections

Picture of Make the Connections

Start with the diagram and refer to the description below if something is not clear.

Here's a nice, large diagram that hasn't been compressed if you need it: WIRING DIAGRAM.

WARNING: Again, do not use the 3.3V pin on the Arduino UNO to power your ESP module. The ESP draws more current than the 3.3V pin can provide.



+3.3V to positive rail of breadboard

GND/Negative to negative rail of breadboard

There is also a 470μF capacitor connected between the positive and negative rails of the breadboard. This is a polarized capacitor so be careful with the wiring: the side with the stripe usually indicates the negative pole, so connect this to the negative rail and the other to the positive rail.



VCC to positive rail of breadboard

GND to negative rail of breadboard

EN (or CH_PD) pulled high (to 3.3V) with a 10kΩ resistor

RST normally pulled high with a 10kΩ resistor but connected to GND when "RESET" button is pushed

GPIO15 pulled down (to GND) with a 10kΩ resistor


  • Normal operation: pulled high with 10kΩ resistor OR floating (not connected to anything)
  • Flashing/uploading: Connected to GND when "FLASH" button is pushed

If you don't want to use the buttons:

  • RST should be pulled high; manually connect-and-disconnect to GND when a reset of the ESP is required; alternative: leave RST pulled high and power off/on the ESP by disconnecting and reconnecting the VCC line
  • GPIO0 should not be connected to anything for normal operation but manually connect it to GND when you want to flash firmware or upload sketches



TX on ESP to TX pin on Arduino (pin #1)

RX on ESP to RX pin on Arduino (pin #0)



RESET pin must be connected to GND pin (this disables board resetting on serial com initialization in Arduino)


If you've connected everything correctly, you should at least see the blue LED on the ESP flash when you reset/reboot it.

Step 2: Open Arduino IDE and the Serial Monitor

Picture of Open Arduino IDE and the Serial Monitor

You should now be all set to communicate with your ESP through the Arduino UNO from the Serial Monitor.

All my ESPs have come preloaded with the AT commands library. That being said, there are people out there saying that their ESPs came with nothing on them initially and that they had to flash one firmware or another. We'll find out either way in this step

Open the Arduino IDE, select the Port to which your Arduino UNO is connected and then open the Serial Monitor.

In the bottom-right corner of the Serial Monitor select 115200 as the baud rate. You should also have "Both NL & CR" selected.

Make sure all the connections from the previous step are correct -- we're aiming for basic operation here, not flashing, so GPIO0 should be pulled high or left disconnected.

Reset/reboot the ESP module. If everything is in order, in the serial monitor you should see some mumbo-jumbo characters at first followed by "ready". If it shows this, you're ready to test a few commands so proceed to the next step.

Step 3: AT Commands

Picture of AT Commands

Now we're ready to type a few commands in the serial monitor. Just type the desired command

Here's a list of the most common commands used.

AT check if the module is connected properly and its functioning, the module will reply with an acknowledgment.
AT+RST reset the wifi module. It's good practice to reset it before or after it has been programmed.

AT+GMR list the firmware version installed on the ESP8266.

AT+CWLAP detect the Access points (wifi networks) available in the area and their signal strengths. LAP means List Access Points

AT+CWJAP=”SSID”,”PASSWORD connects the ESP8266 to the specified SSID in the AT command mentioned in the previous code. JAP means Join Access Point

AT+CWJAP="","" disconnect from all access points

AT+CIFSR display the obtained IP address and the MAC address of the ESP.

AT+CWMODE= sets the wifi mode. Reset with AT+RST after changing wifi mode.

AT+CWMODE? will tell you which wifi mode the module is set to. 1 is STATION (used to connect to other networks, this is what you use to measure sensor data and send it to a website), 2 is Access Point (a wifi network in itself), and 3 is a hybrid STATION-ACCESS POINT.

If you want to go more in-depth with AT commands, here is the official documentation with all the possible AT instructions. And just in case they decide to move it, I've attached the 2016 document below.


In the next tutorial, we'll see how we can use this setup to flash firmware to the ESP-12E with the ESP Flash Tool 2.4.



PrinceG38 (author)2017-11-26

Is there a tutorial for uploading sketch using this connection , thank you

hikaru mounir (author)2017-07-21

thanks a lot for this instructables.

i ve a question :

can i use the same connections as shown in Step 1 ?

knowing that i have ESP-12F and an Arduino UNO R3 (see the picture)

Tstef (author)hikaru mounir2017-08-11

Yes, same connections.

hikaru mounir (author)Tstef2017-11-25

thank's for the answer again,
it's been a while since I loged in to instructables.

I was very busy with my study.


Vito8 (author)2017-11-09

Thanks for the awesome tut. I am able to send the AT commands through the serial monitor, but I cant upload my sketch. How can I upload my sketch to esp-12e and how to communicate with arduino?

Vito8 (author)Vito82017-11-11

ok I got it. I have to press reset and flash to flash some skatches to esp 8266

vinutp1989 (author)2017-10-26

i made the connections as above,initially its worked properly

but some time later i cant send AT comd and whn i reseting serial moritor showing garbage valule what may be the fault i checked mor

pls help me its urgent

Tstef (author)vinutp19892017-10-27

Try connecting a 100nF capacitor between the VCC and GND pads of the ESP module (as close to the pads as possible). Also, try changing the baud rate to 57600 or 76800 and look for error codes when the ESP resets. These are debug baud rates.

GobiN4 (author)2017-09-16

I made the connections as above, but my serial monitor doesn't display any jumbo characters once the RST is pressed.I am using Ai thinker esp 12e board.What may be the fault?

Tstef (author)GobiN42017-09-27

Hmmm, I'm not sure. Does the blue LED on the ESP flash when you connect it?

DerekVR (author)2017-09-26

Thank you for the tutorial! Very interesting. This setup works for me with Arduino Uno as described: can use Serial Monitor and send AT command. But would ask for the advise on how to flash ESP with CH340G. With the same setup I cannot connect to ESP and send any AT commands in Serial Monitor. And upload does not work either: ESP blinks but ends with a standard error: "error: espcomm_open failed".

You mentioned that you were able successfully flash ESP with TTL adapter. Can you please post the instruction on how to do it right?

Tstef made it! (author)DerekVR2017-09-27

Unfortunately, I don't have any experience with the CH340G chip. I was using an FT232RL adapter (like in the image). The connections were as follows:


Pull both GND to a common ground (battery/source negative).
GPIO0 (zero) on the ESP needs to be pulled to GND (if you see flashing on the ESP but you get the connection error it might be because GPIO0 is not pulled to GND).

Oh, and the FT232RL supports both 3.3 and 5V logic -- so if you still have issues with the CH340G, maybe it's because you're trying to work with 3.3V logic on 5V. Sometimes there's a jumper or a switch where you can change this.

chimeranzl (author)2017-08-10

As this is mean't to be for beginners, you should add photo's of the actual board's you're using and connectivity, because if you're using the ESP v12E *DEV* board, it supports 5V for Vin.

Tstef (author)chimeranzl2017-08-11

Normally I would put actual pictures but in this case I don't think they would add any value to the tutorial -- the module is fairly tiny and all those wires would get very confusing. Not to mention that I don't have a camera that would take a good picture, especially not better than the diagram.

tariqms (author)2017-05-28

Thanks alot, it really worked.
One question, can i replace arduino with CH340G.
Second thing is, I am able to run AT commands but unable to flash a sketch using Arduino IDE, do i have keep the flash button pressed while flasing or just press it once.

Tstef (author)tariqms2017-07-12

I think I misunderstood your first question. Did you mean Arduino clones with CH340G instead of an FTDI chip? If yes, then yes, you should have no issues replacing it -- just be sure to have the appropriate drivers installed.

Tstef (author)Tstef2017-07-12

Flashing sketches is a whole other can of worms. I've uploaded sketches straight to the ESP via an FT232RL module (

I know it's possible to do it through an Arduino Uno. Have a look here:

It looks like you need to use the SoftwareSerial library.

Then what you do before uploading the sketch is this chicken dance: (1) hold down the FLASH button (don't let go :P), (2) while holding FLASH, press and release the RESET button, (3) release the FLASH button, (4) upload sketch.

ΗλέκτραΚ (author)2017-07-10

Thanks for sharing! I'm rather new in ESP8266. I follow the steps but the mumbo-jumpo characters in serial monitor don't be followed by "ready". Is this an indication that the AT command library isn't preloaded in my ESP?

Tstef (author)ΗλέκτραΚ2017-07-11

Do the mumbo-jumbo characters stop printing at some point?

I would start by making sure that the baud rate is 115200. If that doesn't work, try 9600 as well.
Also try, 57600 or 76800, these are the debugging baud rates -- you should be able to get some legible info from this. This is where it'll tell you if your module is running intro some kind of error.

Let me know what happens.

FerenczÁ1 (author)2017-05-24


Swansong (author)2017-01-31

Thanks for sharing :)

Tstef (author)Swansong2017-02-01

You're welcome. Hope it helps.

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