Drone Attributes

The attributes contain the state information of the connected drone.

Note that all attributes that are arrays are formatted as numpy arrays.

Here is the list and definition of all the attributes in the drone class:

Attribute	Format	Description
connected	boolean	the connected state of the API to the drone
armed	boolean	whether or not the drone is currently armed. Armed means that the drone's motors are running and ready to take inputs. Until the drone is armed, no motor inputs will create any effects (the motors are effectively turned off until the drone is armed)
guided	boolean	whether or not the drone is currently in a guided mode. Guided mode means that the python script has control of the drone. Until the drone is put into guided mode, no commands sent to it from a script will be executed.
attitude	[roll (degree), pitch (degree), yaw (degree)]	the current attitude of the drone
global_position	[longitude (degree), latitude (degree), altitude (meter)]	the current GPS position of the drone
global_home	[longitude (degree), latitude (degree), altitude (meter)]	the GPS position of the "home" location of the drone
local_position	[north (meter), east (meter), down (meter)]	the current local position of the drone. Local position being defined as the NED position of the drone with respect to some (0,0,0) (the home position)
local_velocity	[vnorth (meter/second), veast (meter/second), vdown (meter/second)]	The current velocity vector of the drone in meters/second, represented in the local NED frame
acceleration_raw	[x (), y (), z ()]	a vector of the raw accelerations measurement of the drone in the body frame
gyro_raw	[x (), y (), z ()]	a vector of the raw gyroscope measurement of the drone in the body frame
barometer	alt (meter)	the current altitude of the drone (in meters) as measured solely by the barometer onboard a vehicle (or simulated)

Listening to Attribute Changes

As new information about the drone is passed to Drone through the connection, various attributes will be updated. Callbacks are functions that can be registered to be called when a specific set of attributes are updated. There are two steps needed to be able to create and register a callback:

1. Create the callback function:

Each callback function you may want needs to be defined as a member function of your custom class that subclasses Drone that takes in only the self parameter. For example, here is the definition of a callback method we may use for when the local position attribute is updated:

class MyDrone(Drone):
    ...

    def local_position_callback(self):
        """ this is triggered when self.local_position contains new data """
        pass

2. Register the callback:

In order to have your callback function called when the appropriate attributes are updated, each callback needs to be registered. This registration takes place in your class's __init__() function as shown below:

class MyDrone(Drone):

    def __init__(self, connection):
        ...

        # register a callback on local position attribute changes
        self.register_callback(MsgID.LOCAL_POSITION, self.local_position_callback)

Since callback functions are only called when certain drone attributes are changed, the first parameter to the callback registration indicates for which attribute changes you want the callback to occur. Here is a list of the different sets of attribute changes you can listen to:

Registration flag	Conditions for triggering callback function
MsgID.ANY	changes in any attribute
MsgID.STATE	changes in either armed or guided
MsgID.GLOBAL_POSITION	changes in global_position
MsgID.LOCAL_POSITION	changes in local_position
MsgID.GLOBAL_HOME	changes in global_home
MsgID.LOCAL_VELOCITY	changes in local_velocity
MsgID.CONNECTION_CLOSED	connection to the drone has been terminated. This means that attributes will no longer be updated and all drone facing commands will not be executed by the drone.
MsgID.RAW_GYROSCOPE	changes in gyro_raw
MsgID.RAW_ACCELEROMETER	changes in acceleration_raw
MsgID.BAROMETER	changes in barometer
MsgID.DISTANCE_SENSOR	reserved
MsgID.ATTITUDE	changes in attitude