ARM M family cores can run each other's code more or less.
Only the libraries for I/O need to be rewritten.
In some cases, there are drop in replacements (Gigadevices STM32 clones)
Only the libraries for I/O need to be rewritten.
In some cases, there are drop in replacements (Gigadevices STM32 clones)
Single chip system, with built in analog comparators, timers, signal capture and PWM generation module, serial UART, etc. I.e., a whole "system on a chip" with the external world interfaces already built into the chip. Changing one of these for an ARM CPU with external analog comparators, timers, PWM modules, serial UART's, etc., is a redesign effort, not just a "change the chip" effort. If the clock speed possible via the internal clock oscillator is sufficient, then this chip needs only +5V and ground (plus programming) to be able to interface to and control some external analog or digital equipment.
I seen a few dashboard where there is an STM32 sitting connected to a single button, whose only duty is to register a key press, and burp something on the CanBus in response.
B) If you did have a $20 microcontroller for Canbus control of a window motor driver but it saved $19 in extra wiring/labor (driver controls usually route to all windows), provides reliable debounce, automated one-push-to-open, and allows things like holding keyless lock to close all windows, it's totally worth it.