Feather is the new development board from Adafruit, and like it's namesake it is thin, light, and lets you fly! We designed Feather to be a new standard for portable microcontroller cores.

This is the Adafruit Feather HUZZAH ESP8266 - our take on an 'all-in-one' ESP8226 WiFi development board with built in USB and battery charging. Its an  ESP8266 WiFi module with all the extras you need, ready to rock! We have other boards in the Feather family, check'em out here.

At the Feather HUZZAH's heart is an ESP8266 WiFi microcontroller clocked at 80 MHz and at 3.3V logic. This microcontroller contains a Tensilica chip core as well as a full WiFi stack. You can progam the microcontroller using the Arduino IDE for an easy-to-run Internet of Things core. We wired up a USB-Serial chip that can upload code at a blistering 921600 baud for fast development time. It also has auto-reset so no noodling with pins and reset button pressings.

To make it easy to use for portable projects, we added a connector for any of our 3.7V Lithium polymer batteries and built in battery charging. You don't need a battery, it will run just fine straight from the micro USB connector. But, if you do have a battery, you can take it on the go, then plug in the USB to recharge. The Feather will automatically switch over to USB power when its available.

Here's some handy specs!

  • Measures 2.0" x 0.9" x 0.28" (51mm x 23mm x 8mm) without headers soldered in
  • Light as a (large?) feather - 6 grams
  • ESP8266 @ 80MHz or 160 MHz with 3.3V logic/power
  • 4MB of FLASH (32 MBit)
  • 3.3V regulator with 500mA peak current output
  • CP2104 USB-Serial converter onboard with 921600 max baudrate for uploading
  • Auto-reset support for getting into bootload mode before firmware upload
  • 9 GPIO pins - can also be used as I2C and SPI
  • 1 x analog inputs 1.0V max
  • Built in 100mA lipoly charger with charging status indicator LED
  • Pin #0 red LED for general purpose blinking. Pin #2 blue LED for bootloading debug & general purpose blinking
  • Power/enable pin
  • 4 mounting holes
  • Reset button

Comes fully assembled and tested, with a USB interface that lets you quickly use it with the Arduino IDE or NodeMCU Lua. (It comes preprogrammed with the Lua interpretter) We also toss in some header so you can solder it in and plug into a solderless breadboard. Lipoly battery and USB cable not included (but we do have lots of options in the shop if you'd like!)

Power Pins

  • GND - this is the common ground for all power and logic
  • BAT - this is the positive voltage to/from the JST jack for the optional Lipoly battery
  • USB - this is the positive voltage to/from the micro USB jack if connected
  • EN - this is the 3.3V regulator's enable pin. It's pulled up, so connect to ground to disable the 3.3V regulator
  • 3V - this is the output from the 3.3V regulator, it can supply 500mA peak (try to keep your current draw under 250mA so you have plenty for the ESP8266's power requirements!)

Logic pins

This is the general purpose I/O pin set for the microcontroller. All logic is 3.3V

The ESP8266 runs on 3.3V power and logic, and unless otherwise specified, GPIO pins are not 5V safe! The analog pin is also 1.0V max!

Serial pins

RX and TX are the serial control and bootloading pins, and are how you will spend most of your time communicating with the ESP module

The TX pin is the output from the module and is 3.3V logic.

The RX pin is the input into the module and is 5V compliant (there is a level shifter on this pin)

These are connected through to the CP2104 USB-to-Serial converter so they should not be connected to or used unless you're super sure you want to because you will also be getting the USB traffic on these!

I2C & SPI pins

You can use the ESP8266 to control I2C and SPI devices, sensors, outputs, etc. While this is done by 'bitbanging', it works quite well and the ESP8266 is fast enough to match 'Arduino level' speeds.

In theory you can use any pins for I2C and SPI but to make it easier for people using existing Arduino code, libraries, sketches we set up the following:

  • I2C SDA = GPIO #4 (default)
  • I2C SCL = GPIO #5 (default)

If you want, you can connect to I2C devices using other 2 pins in the Arduino IDE, by calling Wire.pins(sda, scl) before any other Wire code is called (so, do this at the begining of setup() for example

Likewise, you can use SPI on any pins but if you end up using 'hardware SPI' you will want to use the following:

  • SPI SCK = GPIO #14 (default)
  • SPI MOSI = GPIO #13 (default)
  • SPI MISO = GPIO #12 (default)

GPIO pins

This breakout has 9 GPIO: #0, #2, #4, #5, #12, #13, #14, #15, #16 arranged at the top edge of the Feather PCB

All GPIO are 3.3V logic level in and out, and are not 5V compatible.  Read the full spec sheet to learn more about the GPIO pin limits, but be aware the maximum current drawn per pin is 12mA.

These pins are general purpose and can be used for any sort of input or output. Most also have the ability to turn on an internal pullup. Many have special functionality:

GPIO #0, which does not have an internal pullup, and is also connected a red LED. This pin is used by the ESP8266 to determine when to boot into the bootloader. If the pin is held low during power-up it will start bootloading! That said, you can always use it as an output, and blink the red LED - note the LED is reverse wired so setting the pin LOW will turn the LED on.

GPIO #2, is also used to detect boot-mode. It also is connected to the blue LED that is near the WiFi antenna. It has a pullup resistor connected to it, and you can use it as any output (like #0) and blink the blue LED.

GPIO #15, is also used to detect boot-mode. It has a pulldown resistor connected to it, make sure this pin isn't pulled high on startup. You can always just use it as an output

GPIO #16 can be used to wake up out of deep-sleep mode, you'll need to connect it to the RESET pin

Also note that GPIO #12/13/14 are the same as the SCK/MOSI/MISO 'SPI' pins!

Analog Pins

There is also a single analog input pin called A. This pin has a ~1.0V maximum voltage, so if you have an analog voltage you want to read that is higher, it will have to be divided down to 0 - 1.0V range

Other control pins

We have a few other pins for controlling the ESP8266

  • RST - this is the reset pin for the ESP8266, pulled high by default. When pulled down to ground momentarily it will reset the ESP8266 system. This pin is 3.3V logic only
  • EN (CH_PD) - This is the enable pin for the ESP8266, pulled high by default. When pulled down to ground momentarily it will reset the ESP8266 system. This pin is 3.3V logic only

NC Pins

The rest of the pins are labeled NC which means Not Connected - they are not connected to anything and are there as placeholders only, to maintain physical compatibility with the other boards in the Feather line!

We ship Feathers fully tested but without headers attached - this gives you the most flexibility on choosing how to use and configure your Feather

Header Options!

Before you go gung-ho on soldering, there's a few options to consider!

The first option is soldering in plain male headers, this lets you plug in the Feather into a solderless breadboard

Another option is to go with socket female headers. This won't let you plug the Feather into a breadboard but it will let you attach featherwings very easily

We also  have 'slim' versions of the female headers, that are a little shorter and give a more compact shape

Finally, there's the "Stacking Header" option. This one is sort of the best-of-both-worlds. You get the ability to plug into a solderless breadboard and plug a featherwing on top. But its a little bulky

Soldering in Plain Headers

Prepare the header strip:

Cut the strip to length if necessary. It will be easier to solder if you insert it into a breadboard - long pins down

Add the breakout board:

Place the breakout board over the pins so that the short pins poke through the breakout pads

And Solder!

Be sure to solder all pins for reliable electrical contact.

(For tips on soldering, be sure to check out our Guide to Excellent Soldering).

Solder the other strip as well.

You're done! Check your solder joints visually and continue onto the next steps

Soldering on Female Header

Tape In Place

For sockets you'll want to tape them in place so when you flip over the board they don't fall out

Flip & Tack Solder

After flipping over, solder one or two points on each strip, to 'tack' the header in place

And Solder!

Be sure to solder all pins for reliable electrical contact.

(For tips on soldering, be sure to check out our Guide to Excellent Soldering).

You're done! Check your solder joints visually and continue onto the next steps

Don't power the Huzzah ESP8266 with a CanaKit 5V power supply, these power supplies have been destroying the CP2104 chip.

Battery + USB Power

We wanted to make the Feather HUZZAH easy to power both when connected to a computer as well as via battery. There's two ways to power a Feather. You can connect with a MicroUSB cable (just plug into the jack) and the Feather will regulate the 5V USB down to 3.3V. You can also connect a 4.2/3.7V Lithium Polymer (Lipo/Lipoly) or Lithium Ion (LiIon) battery to the JST jack. This will let the Feather run on a rechargable battery. When the USB power is powered, it will automatically switch over to USB for power, as well as start charging the battery (if attached) at 100mA. This happens 'hotswap' style so you can always keep the LiPoly connected as a 'backup' power that will only get used when USB power is lost.

The JST connector polarity is matched to Adafruit LiPoly batteries. Using wrong polarity batteries can destroy your Feather

The above shows the Micro USB jack (left), Lipoly JST jack (top left), as well as the 3.3V regulator and changeover diode (just to the right of the JST jack) and the Lipoly charging circuitry (right below the regulator).

There's also a CHG LED next to the USB jack, which will light up while the battery is charging. This LED might also flicker if the battery is not connected.

Power supplies

You have a lot of power supply options here! We bring out the BAT pin, which is tied to the lipoly JST connector, as well as USB which is the +5V from USB if connected. We also have the 3V pin which has the output from the 3.3V regulator. We use a 500mA peak low-dropout regulator. While you can get 500mA from it, you can't do it continuously from 5V as it will overheat the regulator. We use this to power the ESP8266 which can draw spikes of 250+mA (although its not continuous).

You should be able to budget about 250mA current available from the regulator, which will leave plenty for the WiFi module.

Measuring Battery

If you're running off of a battery, chances are you wanna know what the voltage is at! That way you can tell when the battery needs recharging. Lipoly batteries are 'maxed out' at 4.2V and stick around 3.7V for much of the battery life, then slowly sink down to 3.2V or so before the protection circuitry cuts it off. By measuring the voltage you can quickly tell when you're heading below 3.7V

Since the ESP8266 does not have multiple ADC pins, we didn't want to 'sacrifice' one for Lipoly battery monitoring. However we do have a tutorial that mentions how to do it, using two resistors. You can check out the wiring diagram here (use the VBat pin to measure) and the code here.

ENable pin

If you'd like to turn off the 3.3V regulator, you can do that with the EN(able) pin. Simply tie this pin to Ground and it will disable the 3V regulator. The BAT and USB pins will still be powered

Alternative Power Options

The two primary ways for powering a feather are a 3.7/4.2V LiPo battery plugged into the JST port or a USB power cable.

If you need other ways to power the Feather, here's what we recommend:

Here's what you cannot do:

  • Do not use alkaline or NiMH batteries and connect to the battery port - this will destroy the LiPoly charger and there's no way to disable the charger
  • Do not use 7.4V RC batteries on the battery port - this will destroy the board

The Feather is not designed for external power supplies - this is a design decision to make the board compact and low cost. It is not recommended, but technically possible:

  • Connect an external 3.3V power supply to the 3V and GND pins. Not recommended, this may cause unexpected behavior and the EN pin will no longer. Also this doesn't provide power on BAT or USB and some Feathers/Wings use those pins for high current usages. You may end up damaging your Feather.
  • Connect an external 5V power supply to the USB and GND pins. Not recommended, this may cause unexpected behavior when plugging in the USB port because you will be back-powering the USB port, which could confuse or damage your computer.

Each Feather HUZZAH ESP8266 breakout comes pre-programmed with NodeMCU's Lua interpreter. As of this writing, we ship with NodeMCU 0.9.5 build 20150318  powered by Lua 5.1.4 but it may be more recent

Lua is still a work in progress, so we strongly recommend visiting NodeMCU and updating your Lua version to the very latest as they have the ability to make you the latest continuous build. Then follow their guide on how to update Lua!

The Lua interpreter runs on the ESP8266 and you can type in commands and read out the results over serial. In order to upload code to the ESP8266 and use the serial console, connect any data-capable micro USB cable to the Feather HUZZAH and the other side to your computer's USB port. Install the required CP2104 USB driver to have the COM/Serial port appear properly

Don't forget to visit esp8266.com for the latest and greatest in ESP8266 news, software and gossip!

Don't forget to install the USB driver for the CP2104 USB-to-Serial chip!

Open up serial console

Next up, on your computer, use a serial console program such as CoolTerm (Mac) or Putty (Windows) or screen (linux). Teraterm seems to dislike the initial 74400bps data stream from the ESP8266 so you can try it but you'll possibly need to reset the terminal software.

  • Connect up to the COM or Serial port used by your cable, at 9600 Baud
  • Make sure you have turned off any hardware handshake or flow control
  • Putty isn't good with pasting code in, so you may not be able to copy-n-paste!
  •  Also make sure you have line endings set to CRLF "\r\n"

Use any serial console program you like, we just happen to be used to Putty!

Once the terminal software is connected, click the Reset button on the Feather HUZZAH ESP8266 board to reset it and have it print out the welcome message:

If you don't get this message, first check that the red/blue leds flickered when you press the reset button. If they didnt, make sure you've got the right baud rate selected in the software (9600)

Hello world!

Ok we can now turn on an LED. There is a red LED on each board, connected to GPIO #0

NodeMCU Lua's pinouts are not the same as the Arduino/gcc pinouts. We print the Arduino pinouts on the board so watch out!
The Lua documentation for the ESP8266 has GPIO #4 and #5 swapped so if #4/#5 aren't working for you, try swapping!

Pin Notes



No pullups!





CHPD (Note, don't use this pin or set it to be an output!)





















So to set the pin #0 LED on and off (which would be pin #3 in Lua) first make it an output:

gpio.mode(3, gpio.OUTPUT)

Turn the LED on with:

gpio.write(3, gpio.LOW)

And off with:

gpio.write(3, gpio.HIGH)

You can make this a little more automated by running a longer script.

For longer text, pasting can be difficult as the lua interpreter needs a little delay time between characters and also require CR-LF settings. For that reason you may want to paste each line and then hit return manually.

while 1 do
  gpio.write(3, gpio.HIGH)
  tmr.delay(1000000)   -- wait 1,000,000 us = 1 second
  gpio.write(3, gpio.LOW)
  tmr.delay(1000000)   -- wait 1,000,000 us = 1 second

The LED will now be blinking on and off.

Note that since its in a loop, its not possible to get it to stop via the interpreter. To stop it, click the Reset button again!

This code halts the processor during the tmr.delay, a smarter way to blink an LED is to use the timer capability to set off the LED control (code from here)

-- Pin definition 
local pin = 3
local status = gpio.LOW
local duration = 1000    -- 1 second duration for timer

-- Initialising pin
gpio.mode(pin, gpio.OUTPUT)
gpio.write(pin, status)

-- Create an interval
tmr.alarm(0, duration, 1, function ()
    if status == gpio.LOW then
        status = gpio.HIGH
        status = gpio.LOW

    gpio.write(pin, status)

Scanning & Connecting to WiFi

We'll continue with a quick demo of scanning for WiFi and connecting.

Once you're back at the Lua prompt, set the ESP8266 into WiFi Client mode with


Then you can run the scanner and have it print out the available AP's

-- print ap list
function listap(t)
      for k,v in pairs(t) do
        print(k.." : "..v)

or for more detail...

-- print ap list
function listap(t)
      for ssid,v in pairs(t) do
        authmode, rssi, bssid, channel = string.match(v, "(%d),(-?%d+),(%x%x:%x%x:%x%x:%x%x:%x%x:%x%x),(%d+)")

We can connect to the access point with wifi.sta.config and wifi.sta.connect - it will take a second or two to complete the connection, you can query the module to ask the status with wifi.sta.status() - when you get a 5 it means the connection is completed and DHCP successful

tmr.delay(1000000)   -- wait 1,000,000 us = 1 second

WebClient example

Once you're got the IP address you can connect to adafruit, for example, and read a webpage and print it out:

sk=net.createConnection(net.TCP, 0)
sk:on("receive", function(sck, c) print(c) end )
sk:send("GET /testwifi/index.html HTTP/1.1\r\nHost: www.adafruit.com\r\nConnection: keep-alive\r\nAccept: */*\r\n\r\n")

You can also have the module do DNS for you, just give it the hostname instead of IP address:

sk=net.createConnection(net.TCP, 0)
sk:on("receive", function(sck, c) print(c) end )
sk:send("GET /testwifi/index.html HTTP/1.1\r\nHost: www.adafruit.com\r\nConnection: keep-alive\r\nAccept: */*\r\n\r\n")

This is just a light overview of testing out your HUZZAH ESP breakout! For much more, check out NodeMCU's documentation page https://nodemcu.readthedocs.io/ for the details on what functions are available to you, as well as  http://www.lua.org to learn more about the Lua scripting language

While the Feather HUZZAH ESP8266 comes pre-programmed with NodeMCU's Lua interpretter, you don't have to use it! Instead, you can use the Arduino IDE which may be more familar. This will write directly to the firmware, erasing the NodeMCU firmware, so if you want to go back to Lua, use the flasher to re-install it

Don't forget to visit esp8266.com for the latest and greatest in ESP8266 news, software and gossip!

In order to upload code to the ESP8266 and use the serial console, connect any data-capable micro USB cable to the Feather HUZZAH and the other side to your computer's USB port.

Don't forget you will also need to install the SiLabs CP2104 Driver:

On Mac OS 10.13 and higher, in addition to installing, you will have to give the CP2104 kernel driver permission to load. You can find out if you need to give additional permission by visiting your Security & Privacy settings system preferences screen after installing and looking for the message that says, 'System software from developer "SiLabs" was blocked from loading', like in the picture below.

To allow the driver to load, click the lock icon, enter your password, and click "Allow" next to the warning message. After that, you may have to restart your computer before following the steps below and connecting to your Huzzah in the Arduino app.

If you are using Mac OS 10.12.6 (Sierra) and you cannot upload with the latest Mac OS VCP driver, please try the legacy v4 driver below. Note you will need to uninstall the v5 driver using uninstall.sh (in the driver package)

Install the Arduino IDE 1.6.8 or greater

Download Arduino IDE from Arduino.cc (1.6.8 or greater) from Arduino.cc

The latest is usually the best

Install the ESP8266 Board Package

Enter http://arduino.esp8266.com/stable/package_esp8266com_index.json into Additional Board Manager URLs field in the Arduino v1.6.4+ preferences.

 Next, use the Board manager to install the ESP8266 package.

If you want to use this board with Adafruit IO Arduino - make sure you're on version 2.5.1 or ABOVE.

After the install process, you should see that esp8266 package is marked INSTALLED. Close the Boards Manager window once the install process has completed.

Setup ESP8266 Support

When you've restarted, select Adafruit Feather HUZZAH ESP8266  from the Tools->Board dropdown

80 MHz as the CPU frequency

You can keep the Flash Sizeat "4M (3M SPIFFS)

For Upload Speed, select 115200 baud (You can also try faster baud rates, we were able to upload at a blistering 921600 baud but sometimes it fails & you have to retry)

The matching COM port for your FTDI or USB-Serial cable

On a mac, you should look for the "SLAB_USBtoUART" port

Blink Test

We'll begin with the simple blink test

Enter this into the sketch window (and save since you'll have to)

void setup() {
  pinMode(0, OUTPUT);

void loop() {
  digitalWrite(0, HIGH);
  digitalWrite(0, LOW);

Now you can simply upload! The Feather HUZZAH has built in auto-reset that puts it into bootloading mode automagically

The sketch will start immediately - you'll see the LED blinking. Hooray!

Connecting via WiFi

OK once you've got the LED blinking, lets go straight to the fun part, connecting to a webserver. Create a new sketch with this code:

 *  Simple HTTP get webclient test

#include <ESP8266WiFi.h>

const char* ssid     = "yourssid";
const char* password = "yourpassword";

const char* host = "wifitest.adafruit.com";

void setup() {

  // We start by connecting to a WiFi network

  Serial.print("Connecting to ");
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {

  Serial.println("WiFi connected");  
  Serial.println("IP address: ");

int value = 0;

void loop() {

  Serial.print("connecting to ");
  // Use WiFiClient class to create TCP connections
  WiFiClient client;
  const int httpPort = 80;
  if (!client.connect(host, httpPort)) {
    Serial.println("connection failed");
  // We now create a URI for the request
  String url = "/testwifi/index.html";
  Serial.print("Requesting URL: ");
  // This will send the request to the server
  client.print(String("GET ") + url + " HTTP/1.1\r\n" +
               "Host: " + host + "\r\n" + 
               "Connection: close\r\n\r\n");
  // Read all the lines of the reply from server and print them to Serial
    String line = client.readStringUntil('\r');
  Serial.println("closing connection");

Dont forget to update

const char* ssid     = "yourssid";
const char* password = "yourpassword";

to your access point and password, then upload the same way: get into bootload mode, then upload code via IDE

Open up the IDE serial console at 115200 baud to see the connection and webpage printout!

That's it, pretty easy!

This page was just to get you started and test out your module. For more information, check out the ESP8266 port github repository for much more up-to-date documentation!

When I connect stuff to some of the pins, the Huzzah stops working. Whats up with that?

The ESP8266 uses some of the pins as 'boot mode' pins so on boot they must be set to certain values:

  • CH_PD (EN) should be always pulled high (it will disable the entire module if low)
  • RST should be always pulled high (it will disable the entire module if low)
  • GPIO 0 sets whether the bootloader is active, it must be pulled HIGH during power up/reset for the user program to run. If it's pulled LOW, it will activate the bootloader. The built-in red LED on #0 pulls it up
  • GPIO 2 must be pulled high on power up/reset.
  • GPIO 15 must be pulled low on power up/reset.
My Huzzah board keeps crashing and resetting, whats up with that?

The most common reason for crashes is power failure. Make sure you're powering the Huzzah with a good ~5V power supply, and if you're using a USB-Serial cable, that it's plugged into the mainboard of your computer or through a powered hub!

I can't seem to find the Serial port on my computer for the Feather HUZZAH?

Don't forget to install the CP2104 VCP drivers for your computer, they are required!

I still can't seem to find the Serial port on my computer for the Feather Huzzah!

Many cheap electronics come with charge-only USB cables, which cause headaches later. Make sure you are using a proper data/sync USB cable. If you find a cable that is charge-only (not data/sync also) throw it out so you don't have the same problem again.

So, I’m getting a 'no such file' error compiling for ESP8266 on my Mac

If your error message looks like this:

fork/exec /Users/xxxxxxx/Library/Arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/1.20.0-26-gb404fb9-2/bin/xtensa-lx106-elf-g++: no such file or directory
Error compiling.

To fix this problem, do this:

  1. Open the Boards Manager in the Arduino IDE
  2. Uninstall the ESP8266 support
  3. go to your ~LIbrary folder (in the Finder, select "Go::Go to folder:, and enter ~Library ). Find the folder Arduino15.
  4. In the Arduino15 folder, go into packages, and delete the folder esp8266
  5. Go back to the Arduino IDE, and install ESP8266 board support.
  6. Now go back to the Finder, and check that you have the xtensa-lx106-elf-g++ file in the path Arduino15/packages/esp8266/tools/xtensa-lx106-elf-gcc/1.20.0-26-gb404fb9-2/bin/xtensa-lx106-elf-g++
  7. That's it!
Whenever I start or reset the ESP8226 there's a bunch of "gibberish" on the Serial console

This is the ROM debug messages, it's transmitted at 74880 baud so you rarely see it in proper 'ascii output' - instead usually it gets corrupted into a bunch of strange characters.

I'm having difficulties uploading to the HUZZAH with the Arduino IDE

Make sure you're using a good quality USB/Serial cable. Install the official drivers for that cable too! We've also noticed that PL2303-based cables don't work on Macs for some reason. FTDI or CP210x based chipsets work best

I tried that, but I'm still having difficulties uploading with the Arduino IDE

Sometimes, it helps to switch the board type to "Generic ESP8266 Module".  Set the Reset Method to "nodemcu"

See this forum post

I'm stuck in bootloader mode and can't upload

You say your led is stuck on dim and you get an error trying to upload? And you're sure your serial cable is connected and working correctly? Well, here's a potential fix: Connect the GPIO0 pin to GND through a 220 ohm resistor. Leave it connected while you upload.  You may have to try it a couple of times, but it should eventually upload and get the HUZZAH unstuck from bootload mode! You can then remove the resistor connection, and your HUZZAH will be happy ever after!

(Note: you may also have to tie RST and EN (CH_PD) together to get this to work.  Remove the connection once you have the module programmed).

Thanks to forum user misslevania for the tip!

I can't get Lua to respond to my commands

Make sure your terminal software is sending correct line endings! The default PuTTY settings may be wrong when trying to talk to Lua on an ESP8266. Lua expects CRLF "\r\n" line endings, and apparently PuTTY defaults to just LF "\n"!

This guide was first published on Nov 25, 2015. It was last updated on Nov 25, 2015.