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Example Setup

Example of a DIY build using a Wemos d1 mini, a Pro Micro, and a Neopixel LED

Main connections

Connect these pins between the two boards:

D1 aka. GPIO 53 aka. SCL
D2 aka. GPIO 42 aka. SDA

Sharing power

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 BoardAtmega32u4
5V or VINRAW, 5V or VIN

DO NOT CONNECT ESP8266 VCC to the ATMEGA32u4 VCC. It will kill the ESP826. Instead, look for the 5V or VIN pin on your dev board, as those will be connected to the regulator.

Adding the LED

To add a Neopixel (WS2812b) LED:

Atmega32u4Neopixel LED
7*DI aka. Data, In
5V aka. VCC5V aka. VCC

* The Data pin can be changed later in the software. Pin 7 is just an example.