Connect these pins between the two boards:
Ideally, you want the Atmega32u4 to power the ESP8266, so it can run on one USB connection instead of always having to plug in both. To share power between them, you need a voltage regulator to provide 3.3V for the ESP8266. Luckily most boards have such a regulator on board.
|ESP8266 Dev Board||Atmega32u4|
DO NOT CONNECT ESP8266 VCC to the ATMEGA32u4 VCC. It will kill the ESP826. Instead, look for the
VIN pin on your dev board, as those will be connected to the regulator.
Adding the LED
To add a Neopixel (WS2812b) LED:
* The Data pin can be changed later in the software. Pin 7 is just an example.