PwmPin: allow get_duty to return the old value for some time #140
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PWM is often implemented in a buffered way to allow glitch-free operation; as a result, implementing a strict "you get what you last set" is not feasible for some implementations.
This change allows the implementation to decide which value to return for
get_duty
while it is being changed. The current wording is "current duty cycle", which seems to be quite clear but deviates from the usual semantics of getters and setters in a way that can lead to different interpretations.In particular, the EFM32 implementation gives the old value until the cycle has actually been changed (at least since a semi-related WIP bugfix) -- but it seems to me that it makes sense to allow that given how it can be implemented, especially considering that basic embedded-hal traits should be widely implementable.
Alternatives:
set_duty
has been called, this reports the old duty cycle until the change has been executed." or similar.