The MSPM0C1104 is a 24 MHz Arm Cortex-M0+ based device with up to 16 KB of flash and 1 KB of SRAM. It has a 12-bit ADC with three channels, six GPIO pins, and typical communication interfaces like UART, SPI, and I²C. It is an ultra-low-power 32-bit MCU well suited for compact battery-powered designs.
Whilst this wouldn’t work for this specific application we’re discussing (no USB support, no wireless), it’s an amazing example of just how little a microcontroller can be nowadays.
Released last year, TI MSPM0C1104
https://www.electronics-lab.com/texas-instruments-unveils-mspm0c1104-worlds-smallest-microcontroller-for-space-constrained-applications/
Whilst this wouldn’t work for this specific application we’re discussing (no USB support, no wireless), it’s an amazing example of just how little a microcontroller can be nowadays.