16 MHz 8-bit core with 8 KB Flash — what fits in that budget
The STM8S903F3P6TR is an 8-bit MCU from ST's STM8S value line, built around the STM8 core running at 16 MHz. Five 10-bit ADC channels handle analog inputs like thermistors or potentiometers, while the I²C, SPI, and UART interfaces connect to common peripherals — think a temperature sensor on I²C and a serial display on UART.
The 8 KB Flash (8K x 8) is the program memory limit. For a simple control loop — reading a sensor, running a PID, driving a PWM output — that's enough. But if you're adding a bootloader, a communication stack, or lookup tables, the budget gets tight. The 1 KB RAM handles stack, global variables, and small buffers; don't plan on large frame buffers or deep FIFOs. The 640-byte EEPROM is handy for calibration constants or configuration parameters that survive power loss, with no need for external serial EEPROM.
Peripherals and I/O — 16 pins, five ADC channels, standard serial buses
With 16 I/O pins in a 20-TSSOP package, every pin counts. The 5-channel 10-bit ADC shares pins with digital I/O, so you trade analog inputs for GPIO. The connectivity set — I²C, SPI, UART/USART — covers the basics: I²C for local sensors or EEPROM, SPI for faster data transfer to a display or ADC, UART for debug or RS-485 conversion.
The ROHS3 compliance covers EU and most global markets.