A low gyro cutoff is needed for most medium/large size drones as the structural natural and blade-pass frequencies are low.
A higher value is still desirable for small platforms surch as racers
or well isolated autopilots and should be tuned by the user.
Specific values for config files are untouched.
The cutoff filter for the D term is disabled here as the required
cutoff frequency for the default D term of the rate controller is higher
than the gyro cutoff. In that case, enabling the D term cutoff would
just add some undesired phase lag to the derivative.
By using the uORB::Subscription API we use a separate subscription
rather than `orb_copy` on the existing file descriptor used in
sensors through `px4_poll`.
This fixes a very peculiar problem that we observed in SITL in CI for
fixedwing. The events were as follows:
1. `sensors` does `px4_poll` on the gyro topic (as normal), and gets
the latest sample using `orb_copy`.
2. A parameter update happens when the mag is initialized and triggers
`VotedSensorsUpdate::parameters_update()` where `orb_copy` happens
before the main loop in `sensors` has started a `px4_poll`.
3. `sensors` now does the `px4_poll`, however waits indefinitely because
it has already copied the latest sample.
Also, the `px4_poll` will never time out because in lockstep the
simulator waits for the next actuator control message which it never
gets and therefore it never sends the next sensor message with a new
timestamp to advance the time.
This only happens for fixedwing because there is only one "uORB path"
through the system unlike for multicopter where a gyro sample can get
picked up by either `sensors` or directly `mc_att_control`, so the
system can survive if `sensors` has "drops".
Temperature compensation is not supported in HITL. Therefore, don't try
and fail. This basically removes the confusing error message that we get
in HITL.
Modules generally do not check for a valid timestamp, thus we need to avoid
publishing invalid data.
This is for example problematic in the attitude_estimator_q, if the
system has no mag: it will copy the (invalid) data and then fails to
initialize, as there is no more mag data coming in.
When a gyro driver is stopped, the topic is unadvertised and
orb_group_count() returns a smaller count. This can have the effect, that
we poll on a certain gyro fd, but since _gyro.subscription_count is reduced
we never do the orb_copy for that fd.
This cannot happen when armed. And only someone playing with the shell
can trigger it (sensor failures do not have that effect).
A reason for using switch arming in the first place is that you cannot
accidentally disarm in-air with the sticks during acrobatic flights.
It also adds a low-throttle arming requirement for switch arming.
Daniel Agar