- parameter updates can be quite expensive because they trigger nearly all modules to reload all of their parameters immediately
- limit modules from updating faster than once per second
_num_outputs is set according to the mode_pwmX call, which is required
for camera triggering.
This fixes camera triggering via PWM, as it avoids overwriting the channel.
- this is done to minimize real end-to-end latency
- actual pulse width only updated for next period regardless of output module
- add cycle interval perf counter