04 Autonomous drone programming in Python

Introduction

Please check our online course (slides or videos) to understand:

• how to connect to the flight controller
• what's the general software architecture
• how to use yocto or ubuntu or the linux OS of choice in a container

PyMAVLINK hello world

Here's a simple python script using the basic pymavlink wrapper to arm the motors for 3 seconds. Arming the motors is the simplest action we can test to show everything is connected. Note: we're using tcp:127.0.0.1:5760 to connect to the flight controller, as we'll do for all the following examples.

UNPLUG THE PROPELLERS BEFORE RUNNING THIS CODE. WE INSIST.

#!/usr/bin/python
from __future__ import print_function

import pymavlink.mavutil as mavutil
import sys

mav = mavutil.mavlink_connection('tcp:127.0.0.1:5760')
mav.wait_heartbeat()
mav.mav.command_long_send(mav.target_system, mav.target_component,
                          mavutil.mavlink.MAV_CMD_COMPONENT_ARM_DISARM, 0, 1,
                          0, 0, 0, 0, 0, 0)
sleep(3)
mav.mav.command_long_send(mav.target_system, mav.target_component,
                          mavutil.mavlink.MAV_CMD_COMPONENT_ARM_DISARM, 0, 0,
                          0, 0, 0, 0, 0, 0)

DroneKit hello world

It’s important to know the basics of MAVLINK, as it the base of all communications with the Flight Controllers. But coding frames with python-mavlink is not developer friendly. DroneKit, developed by 3D Robotics, is one of the friendly python abstractions available under Apache v2 Licence : python.dronekit.io To install on Intel Aero:

pip install dronekit

UNPLUG THE PROPELLERS BEFORE RUNNING THIS CODE. WE INSIST.

Here's the code, still arming the motors for 5 seconds:

#!/usr/bin/python
from dronekit import connect, VehicleMode, LocationGlobalRelative
import time

vehicle = connect('tcp:127.0.0.1:5760', wait_ready=True)
print "Arming motors:"
vehicle.mode    = VehicleMode("GUIDED")
vehicle.armed   = True
while not vehicle.armed:
        print "  Waiting for arming to be finished"
        time.sleep(1)
print "Keeping motors armed for 5s"
time.sleep(5)
print "Disarming"
vehicle.armed   = False

Peripherals

Intel Aero board LEDs

There's a multicolor LED on top of the board (if the board is in the enclosure, you can see the light from the white cable hole), and an orange LED under the board. And here is a sample code to test all the colors:

import time
from periphery import GPIO

print "Top LED Blue"
gpio = GPIO(403, "out")
gpio.write(bool(1))
time.sleep(1)
gpio.write(bool(0))
gpio.close()

print "Top LED Green"
gpio = GPIO(397, "out")
gpio.write(bool(1))
time.sleep(1)
gpio.write(bool(0))
gpio.close()

print "Top LED Red"
gpio = GPIO(437, "out")
gpio.write(bool(1))
time.sleep(1)
gpio.write(bool(0))
gpio.close()

print "Bottom LED Orange"
gpio = GPIO(507, "out")
gpio.write(bool(1))
time.sleep(1)
gpio.write(bool(0))
gpio.close()

CAN

The Intel Aero Compute Board includes a MCP2515 CAN controller and MCP2562 CAN transceiver. The controller is connected to the Atom processor via the SPI interface on bus 1 (SPI1) chip select 0 (CS0). It can be accessed via spidev as /dev/spidev1.0. Python spidev libraries