ESP32 Dev Module WiFi + bluetooth 4MB Flash Development Boardfor Arduino - products that work with official Arduino boards

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. The regulator can supply 500mA peak but half of that is drawn by the ESP32, and it's a fairly power-hungry chip. So if you need a ton of power for stuff like LEDs, motors, etc. Use the USB or BAT pins, and an additional regulator

Logic pins:

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

The ESP32 runs on 3.3V power and logic, and unless otherwise specified, GPIO pins are not 5V safe!

Serial pins:

RX and TX are the additional Serial1 pins, and are not connected to the USB/Serial converter. That means you can use them to connect to UART-devices like GPS's, fingerprint sensors, etc.

The TX pin is the output from the module. The RX pin is the input into the module. Both are 3.3V logic

I2C & SPI pins:

You can use the ESP32 to control I2C and SPI devices, sensors, outputs, etc. If using with , the standard Wire and SPI devices work as you'd expect!

Note that the I2C pins do not have pullup resistors already! You must add them if you want to communicate with an I2C device

GPIO & Analog Pins:

There are tons of GPIO and analog inputs available to you for connecting LEDs, buttons, switches, sensors, etc. Here's the remaining pins available.

Bottom row:

A0 - this is an analog input A0 and also an analog output DAC2. It can also be used as a GPIO #26