Velocity PID Programming: Terms dependent on time

[Ether]

Originally Posted by kenfox

WPILib uses these routines outside of critical regions, so I assume they are either lock-free or have their own independent locks.

My concern was along the following lines. If any of the layers has code like this (pardon the X86speak):

INCORRECT!!
cli   // disable interrupts
/* do something uninterruptable here */
sti   // enable interrupts

... instead of this:

CORRECT:
pushf // save interrupt state
cli   // disable interrupts
/* do something uninterruptable here */
popf  // restore saved interrupt state

.. then you can't reliably use cli in your application code.

It looks like the FPGA clock is preferred since the other ways of grabbing a timestamp aren't used by WPILib except in Vision.

What the overhead of accessing the FPGA, compared to reading the PPC clock?

Testing may be the best way to answer these questions ... I'll collect some data on our cRIOs tomorrow.

Excellent !