To the outside world, the AHRS can be in one of only a few
primary states:
Not present - AHRS is absent or non-responsive via SPI
Inactive - Only link-level status messages are processed
Ready - Ready to receive the next application level message
Busy - Application level message is being processed
Internal to the AHRS, there are many more states that need to be
managed. This FSM provides the necessary decoupling between the
ISR (which is being driven by the SPI link) and the AHRS main
processing loop which must continue to run its filters independently
of the SPI messaging rate.
With this structure, SPI messages can be received at any time but
processed at only specific points within the filter chains.
git-svn-id: svn://svn.openpilot.org/OpenPilot/trunk@1005 ebee16cc-31ac-478f-84a7-5cbb03baadba
