MAVLink's mission protocol: upload, download and clear a mission, geofence or rally point list.

items = [
  [command: :mav_cmd_nav_takeoff, frame: :mav_frame_global_relative_alt, z: 20.0],
  [command: :mav_cmd_nav_waypoint, frame: :mav_frame_global_relative_alt,
   x: 473_977_420, y: 85_455_940, z: 30.0, autocontinue: 1]
]

MAVLink2.Mission.upload(link, {1, 1}, items)
#=> {:ok, opaque_id}

The link's dialect must have the messages (common.xml does). target is {sysid, compid}.

An item has MISSION_ITEM_INT's fields other than the target, seq and mission_type: :frame (a MAV_FRAME atom or value), :command (a MAV_CMD atom or value), :current, :autocontinue, :param1..:param4, :x, :y (integers: degrees × 10^7 for a global frame, metres × 10^4 for a local one) and :z; each defaults to 0. The _INT global frames are superseded by their plain counterparts (:mav_frame_global_relative_alt for :mav_frame_global_relative_alt_int), which mean the same here.

Uploading sends MISSION_COUNT and then each item the target asks for, by MISSION_REQUEST_INT or the deprecated MISSION_REQUEST (answered with MISSION_ITEM_INT either way), until its MISSION_ACK. Downloading asks for the count and then each item by MISSION_REQUEST_INT, accepts the deprecated MISSION_ITEM in reply (its float positions scaled to integers), and acks the whole. When the target goes quiet, the last message is sent again, up to :retries times in a row; after that the operation is cancelled with a MISSION_ACK of MAV_MISSION_OPERATION_CANCELLED and returns {:error, :timeout}.

upload/4 returns {:ok, opaque_id} and download/3 {:ok, items, opaque_id}: the plan's id from the target's MISSION_ACK or MISSION_COUNT, to compare with MISSION_CURRENT later, or nil for a dialect or target without it.

Options:

A refusal is {:error, {:mission_result, result}}, with result the MAV_MISSION_RESULT entry atom (:mav_mission_no_space, ...).