Add Mount option to retract on landing

[peterbarker]

No description provided.

[amilcarlucas]

@bitmask metadata documentation is missing

[rmackay9]

This is fine. An alternative implementation (which I suspect you also thought of) was to pass the is_landing() state into the mount and let it decide if the state has changed. It's no big deal but done that way we might move a bit more code into AP_Mount if we choose to implement this for Plane as well.

[peterbarker]

Yep, I certainly did consider that. But then I thought that other libraries might also want to know when we've just transitioned into landing. Kind if figured we'd see which way things went.

It also briefly crossed my mind to use Notify events but quickly discarded that concept.

[peterbarker]

@bitmask metadata documentation is missing

Fixed, thanks!

[nexton-winjeel]

How urgently do you want this capability in? We've got a similar feature that is vehicle-agnostic that:

• uses the AHRS to get height above ground (falling back to height above home)
• will auto-deploy when altitude goes above parameterised DEPLOY_ALT
• will auto-retract when altitude falls below parameterised RETRACT_ALT

Haven't pushed a PR for it yet because we never flight tested it enough (but we do have SITL tests).

[peterbarker]

How urgently do you want this capability in? We've got a similar feature that is vehicle-agnostic that:

Well, given this isn't merged, can't be that much.

ATM we're using modifications to MAVProxy to accomplish our goals, but it would be nice to do this in AP.

* uses the AHRS to get height above ground (falling back to height above home)

* will auto-deploy when altitude goes above parameterised `DEPLOY_ALT`

* will auto-retract when altitude falls below parameterised `RETRACT_ALT`

Haven't pushed a PR for it yet because we never flight tested it enough (but we do have SITL tests).

Definitely interested in seeing those patches.

[rmackay9]

This looks mergeable to me as-is. Maybe first person to raise the PR wins and we merge this?

[peterbarker]

How urgently do you want this capability in? We've got a similar feature that is vehicle-agnostic that:

* uses the AHRS to get height above ground (falling back to height above home)

* will auto-deploy when altitude goes above parameterised `DEPLOY_ALT`

* will auto-retract when altitude falls below parameterised `RETRACT_ALT`

Haven't pushed a PR for it yet because we never flight tested it enough (but we do have SITL tests).

See also #12042 - which might be closed when we see your PR :-)