Bare-Metal support for Interrupts

As usual, the designer faces a choice. Options are:
No interrupts
Single-task or cooperative multi-tasking
Easiest and safe approach
Allows jitterless operation, if well done
Doesn't scale up to complex situations

Single-interrupt system
The critical "task" is jitterless (the rest is not)
The rest of the system works as before
You can manage a lockless protocol for data-sharing

Full peripheral interrupts
UART, SPI, timers, gpio, ...

System tick alone
With polling I/O in each task

Full preemption and interrupt-driven stuff
Like a desktop/server system