TL;DR
The Adafruit ADS7128 is an 8-channel Analog-to-Digital Converter (ADC) and General Purpose Input/Output (GPIO) expander that combines the functionality of both types of devices. It can operate on either 3.3V or 5V logic, and each of its eight I/O pins can be configured individually. This means you can set them up for 12-bit Successive Approximation Register (SAR) analog input, as well as push-pull or open-drain digital output, or digital input.