STM32 - Timers - Measuring Time

Each of the STM32 parts has multiple timers, and some are better than others for measuring the duration of a function.

I firmly believe until you actually measure the time a function takes, you are just guessing,
thinking "the function is working just fine"....
But, to measure the duration of many functions, you need a time base much finer than an OS Tick.
Micro-second resolution is required.
Although I'd like a 32 bit timer, not all the STM32 parts have one.
I'm pretty sure all have at least a 16-bit timer.  Let's choose an unused timer, and get it
counting micro-second units of time.