Memory budget: 8 KB Flash, 4 KB SRAM
8 KB of Flash limits firmware to small-footprint applications. 4 KB of SRAM is enough for a few hundred bytes of stack, a modest data buffer, and global variables for a dozen I/O points.
Peripherals and I/O for a compact control board
28 GPIOs in a 32-pin package means most pins are shared with the serial interfaces (I2C, SPI, UART/USART) and the 8-channel 10-bit ADC. Plan the pin allocation early: the ADC inputs occupy port 0 pins, and the serial interfaces share alternate functions on the same port.