PCF8591 has one 8 bit ADC on board for 4 channels. The ADC is 8 bit and quite fast. At 100 KHz one gets more than 2000 reads per second for read() and more than 2000 writes per second for write().

A low-power, compact keypad module based on the STM32L010K4T6 microcontroller. This project includes a 12-button keypad interfaced with a host MCU via I2C or UART, designed to serve as a mini keyboard ...

What’s the use of waiting around for something to break in order to hack into something else? As long as it’s just sitting around not being used, who cares? [OmniSaiRen] had a Behringer MIDI ...