knmcguire/pprzlink

Message and communication library for the Paparazzi UAV system

PPRZLINK

Overview

PPRZLINK is a messages toolkit (message definition, code generators, libraries) to be used with [Paparazzi UAV System] (https://paparazziuav.org) and compatible systems. One tool that uses PPRZLINK is the Flying Robot Commander, a web based, RESTful application for controlling multiple aircraft.

Documentation

Documentation is in the doc subdirectory and can be viewed on https://pprzlink.readthedocs.org

To build the docs locally:

sudo pip install sphinx sphinx-autobuild phinx_rtd_theme
cd doc && make html

Libraries

PPRZLINK libraries are available for the following programming languages:

• C
• ocaml
• python
• Rust

Messages

Messages are defined in the messages.xml file and are grouped into the following message classes:

• telemetry
• datalink
• ground
• alert
• intermcu

Please reference Paparazzi Messages Document for a more detailed overview.

Message Classes

Telemetry

Telemetry messages are sent from the aircraft to the ground and are defined in the telemetry class of the messages.xml file.

Datalink

Datalink messages are sent from the ground to the aircraft and are defined in the datalink class of the messages.xml file.

Ground

Ground messages are sent to the ground network agents(GCS, server, link, etc...) and are defined in the ground class of the messages.xml file.

Alert

TBD

InterMCU

TBD

Python Library

The python PPRZLINK ivy interface is defined in ivy.py. There is also a serial version of the interface in serial.py.

Ivy Message Call Sequence

Add Libraries to the Search Path

# if PAPARAZZI_SRC not set, then assume the tree containing this file is a reasonable substitute
PPRZ_SRC = getenv("PAPARAZZI_SRC", path.normpath(path.join(path.dirname(path.abspath(__file__)), '~/paparazzi/')))

sys.path.append(PPRZ_SRC + "/sw/ext/pprzlink/lib/v1.0/python")

from pprzlink.ivy  import IvyMessagesInterface
from pprzlink.message   import PprzMessage
...

Create an Interface Instance

ivy_interface = IvyMessagesInterface("FlyingRobotCommander", start_ivy=False)
...

Subscribe to a Set of Messages

ivy_interface.subscribe(callback_aircraft_messages)
...

Start the Interface

ivy_interface.start()
...

Send Messages

# Main Loop
ivy_interface.send(msg)
ivy_interface.send_raw_datalink(msg)
...

Stop the Interface

ivy_interface.shutdown()
...

Ivy Message Construction

It's easy to construct messages to send over the ivy message bus. Here are a few example python functions for reference.

Datalink Message

def guidance(ac_id, flag, x, y, z, yaw):
    msg = PprzMessage("datalink", "GUIDED_SETPOINT_NED")
    msg['ac_id'] = ac_id
    msg['flags'] = flag
    msg['x']     = x
    msg['y']     = y
    msg['z']     = z
    msg['yaw']   = yaw

    ivy_interface.send_raw_datalink(msg)

Ground Message

def flightblock(ac_id, fb_id):
    msg = PprzMessage("ground", "JUMP_TO_BLOCK")
    msg['ac_id']    = ac_id
    msg['block_id'] = fb_id

    ivy_interface.send(msg)

Subscribing to Ivy Messages

TBD - Describe how to subscribe to message classes