MCP2221A USB to GPIO ADC I2C Breakout Board Adafruit MCP2221A USB to GPIO ADC I2C Breakout Board allows users to drive a tiny OLED display, read a color sensor, or even flash some LEDs directly from a computer. The breakout board is based on the MCP2221A, a USB-to-UART/I2C converter from Microchip. The chip is similar to a USB-to-serial converter but also adds a GPIO and I2C interface. The analog/digital GPIO pins can act as 10-bit analog inputs (ADC), and a 5-bit DAC output is included. The I2C interface is great for talking to OLEDs, sensors, and PWM drivers. The user can use the GPIO to do things like flash LEDs, read switches or buttons, and more.