Companion computer integration (Raspberry Pi) in Drone Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of MAVLink message parsing code

What is the output of this Python code snippet running on a Raspberry Pi receiving MAVLink messages?

Drone Programming

from pymavlink import mavutil

master = mavutil.mavlink_connection('udp:127.0.0.1:14550')
msg = master.recv_match(type='HEARTBEAT', blocking=True)
print(f"System ID: {msg.get_srcSystem()}, Component ID: {msg.get_srcComponent()}")

A AttributeError: 'NoneType' object has no attribute 'get_srcSystem'

B System ID: 1, Component ID: 1

C System ID: 0, Component ID: 0

D TimeoutError: No message received

💡 Hint

The code waits for a heartbeat message and prints its source IDs.

The code connects to a MAVLink UDP endpoint and blocks until it receives a HEARTBEAT message. The typical system and component IDs for a simulated vehicle are 1 and 1.

🧠 Conceptual

intermediate

Purpose of companion computer in drone systems

What is the main role of a companion computer like a Raspberry Pi in a drone system?

A To act as a GPS receiver only

B To control the drone's motors directly

C To replace the flight controller entirely

D To provide advanced processing and run custom algorithms alongside the flight controller

💡 Hint

Think about tasks that require more computing power than the flight controller.

The companion computer runs complex tasks like computer vision, path planning, or data logging, while the flight controller handles low-level motor control and stabilization.

🔧 Debug

advanced

Identify the error in MAVLink connection code

What error will this Raspberry Pi Python code produce when trying to connect to a drone via serial port?

Drone Programming

from pymavlink import mavutil

master = mavutil.mavlink_connection('/dev/ttyUSB0', baud=57600)
msg = master.recv_match(type='ATTITUDE', blocking=True)
print(msg)

A SyntaxError: invalid syntax in baud parameter

B AttributeError: 'NoneType' object has no attribute 'recv_match'

C FileNotFoundError: [Errno 2] No such file or directory: '/dev/ttyUSB0'

D TimeoutError: No ATTITUDE message received

💡 Hint

Check if the serial device path exists on the Raspberry Pi.

If the serial device '/dev/ttyUSB0' is not connected or does not exist, Python raises a FileNotFoundError when trying to open it.

📝 Syntax

advanced

Correct syntax for sending MAVLink command

Which option correctly sends a MAV_CMD_NAV_TAKEOFF command using pymavlink on a Raspberry Pi?

Drone Programming

master = mavutil.mavlink_connection('udp:127.0.0.1:14550')

# Send takeoff command here

A master.mav.command_long_send(master.target_system, master.target_component, mavutil.mavlink.MAV_CMD_NAV_TAKEOFF, 0, 0, 0, 0, 0, 0, 0, 10)

B master.mav.command_long_send(master.target_system, master.target_component, MAV_CMD_NAV_TAKEOFF, 0, 0, 0, 0, 0, 0, 0, 10)

C master.mav.command_long_send(master.target_system, master.target_component, mavutil.MAV_CMD_NAV_TAKEOFF, 0, 0, 0, 0, 0, 0, 0, 10)

D master.mav.command_long_send(master.target_system, master.target_component, mavutil.mavlink.MAV_CMD_NAV_TAKEOFF, 1, 0, 0, 0, 0, 0, 0, 10)

💡 Hint

Check the full path and parameters for the MAV_CMD_NAV_TAKEOFF constant and command_long_send signature.

The correct constant is mavutil.mavlink.MAV_CMD_NAV_TAKEOFF. The first parameter after command is confirmation (0 means no confirmation). The altitude is the last parameter (10 meters).

🚀 Application

expert

Number of GPS fix messages received in 10 seconds

A Raspberry Pi companion computer listens to GPS_RAW_INT MAVLink messages at 5 Hz. How many GPS fix messages will it receive in 10 seconds?

A 50

B 100

C 5

D 10

💡 Hint

Multiply the message frequency by the time interval.

At 5 messages per second, in 10 seconds the total messages received are 5 * 10 = 50.