Believe it or not, changing / 2^31 to >>31 saved 256 bytes in the "d" segment.
The reason is that GCC version prior to 4.3.5 does not have a count_leading_zeros (clz) assembler macro, so it uses a 256 byte lookup table called _clz
The _clz table gets pulled in if you do 64 bit division.
This tiny change is the only place that we do long long division.
Changing to a shift saves 256 bytes of ram.
moved enums to give more room for additional PIDs for Loiter
added new Acro_P gain
added auto_land_enabled option
added pi_loiter_lon and pi_loiter_lat for separate tuning of loiter
when we are in the final stages of a landing (less than 2 seconds from
landing waypoint, or less than 3m above landing altitude) we switch
the navigation to use a fixed course. The code previously used the
crosstrack_bearing for this, but this can lead to a large nav_roll in
this final stage of the approach, which can put a wing into the
runway. In autotest we were seeing a nav_roll value of -45 degrees as
we crossed the transition point for the landing, which often led to a
crash.
This changes the code to use the current yaw_sensor value instead,
which is much less likely to lead to large rolls in the final landing
stages.
hold_course is either -1 (for disabled) or a course to hold for
takeoff/landing. This makes the code a bit clearer.
It also resets hold_course in all non-auto modes, to ensure it isn't
used
If you include airspeed, throttle or groundspeed changes in a mission
then those should not be saved to EEPROM, as otherwise if you restart
and re-fly the mission you will be starting with different parameters
to the ones you used for the first flight.
This is particularly important for setting the target airspeed when
coming in for a landing. You typically set a low target, but if you
fly again the next day I think it would be a real surprise to find
that your loiter airspeed has then changed to the value from the
landing part of your last mission.
This one can be argued either way, but I think that not saving these
changes is the more conservative choice, and better fits the
'principal of least surprise'
