OnsparkF<MILLIS>
When the blade turns on, this function starts returning 32768, then fades back to zero over MILLIS milliseconds. This is intended to be used with Mix<> or AlphaL<> to to create a flash of color or white when the blade ignites.
Mix, AlphaL
https://github.com/profezzorn/ProffieOS/blob/6f8add544c627172ad2dd698c90e5e55078a420a/functions/on_spark.h#L4