Connection over MAVLink protocol in Drone Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize a MAVLink connection over UDP.

Drone Programming

connection = mavutil.mavlink_connection('[1]')

Drag options to blanks, or click blank then click option'

Aserial:/dev/ttyUSB0:57600

Btcp:192.168.1.1:5760

Cudp:127.0.0.1:14550

Dudp:0.0.0.0:14540

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'tcp:' instead of 'udp:' for UDP connection.

Wrong IP address format.

To connect over UDP, the address format is 'udp:IP:port'. Here, 'udp:127.0.0.1:14550' initializes a UDP connection on localhost port 14550.

2fill in blank

medium

Complete the code to wait for a heartbeat message from the drone.

Drone Programming

connection.[1]()

Drag options to blanks, or click blank then click option'

Asend_heartbeat

Bwait_heartbeat

Crecv_match

Dheartbeat

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'send_heartbeat' which sends a heartbeat instead of waiting.

Using 'recv_match' which receives any message, not specifically heartbeat.

The method wait_heartbeat() waits until a heartbeat message is received from the drone, confirming the connection.

3fill in blank

hard

Fix the error in the code to receive a message with a timeout of 5 seconds.

Drone Programming

msg = connection.[1](timeout=5)

Drag options to blanks, or click blank then click option'

Arecv_match

Bwait_heartbeat

Csend_message

Drecv_msg

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'wait_heartbeat' which waits only for heartbeat.

Using 'recv_msg' which is not a valid method.

The correct method to receive any MAVLink message with a timeout is recv_match(). Other options are incorrect or do not support timeout.

4fill in blank

hard

Fill both blanks to create a dictionary of message names and their IDs for messages with ID less than 50.

Drone Programming

msg_dict = {msg.get_type(): msg.msgid for msg in connection.mav.__dict__.values() if msg.[1] < [2]

Drag options to blanks, or click blank then click option'

Amsgid

B50

Cmsg_type

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'msg_type' which is not an attribute.

Using 100 instead of 50 for filtering.

Each MAVLink message object has a msgid attribute for its ID. We filter messages with msgid < 50.

5fill in blank

hard

Fill all three blanks to send a command long message with target system, component, and command ID.

Drone Programming

connection.mav.command_long_send([1], [2], [3], 0, 0, 0, 0, 0, 0, 0, 0)

Drag options to blanks, or click blank then click option'

Atarget_system

Btarget_component

Ccommand

Dmavlink_version

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'mavlink_version' which is unrelated.

Mixing order of parameters.

The command_long_send method requires target_system, target_component, and command as the first three parameters to specify the recipient and command.

Practice

1.

What is the main purpose of using mavutil.mavlink_connection() in drone programming?

easy

A. To establish a communication link with the drone using MAVLink protocol

B. To send video streams from the drone camera

C. To update the drone's firmware automatically

D. To control the drone's battery charging process

Solution

1. Step 1: Understand the function purpose

   mavutil.mavlink_connection() is designed to create a connection channel to communicate with the drone.

2. Step 2: Identify the correct use case

   This function is not for video, firmware, or battery control but for establishing communication over MAVLink.

3. Final Answer:

   To establish a communication link with the drone using MAVLink protocol -> Option A

4. Quick Check:

   Connection function = Establish communication [OK]

Hint: Remember: connection function opens communication channel [OK]

Common Mistakes:

• Confusing connection with video streaming
• Thinking it updates firmware automatically
• Assuming it controls battery charging

2.

Which of the following is the correct way to create a MAVLink connection to a drone on UDP port 14550?

import pymavlink.mavutil as mavutil

connection = ?

easy

A. mavutil.mavlink_connection('http://127.0.0.1:14550')

B. mavutil.mavlink_connection('tcp:127.0.0.1:14550')

C. mavutil.mavlink_connection('serial:/dev/ttyUSB0:115200')

D. mavutil.mavlink_connection('udp:127.0.0.1:14550')

Solution

1. Step 1: Identify the protocol and address format

   UDP connections use the format 'udp:IP:port'. Here, 'udp:127.0.0.1:14550' is correct for UDP on port 14550.

2. Step 2: Eliminate incorrect protocols

   TCP and serial are different protocols; HTTP is not used for MAVLink connections.

3. Final Answer:

   mavutil.mavlink_connection('udp:127.0.0.1:14550') -> Option D

4. Quick Check:

   UDP connection string = 'udp:IP:port' [OK]

Hint: UDP uses 'udp:IP:port' format for connection strings [OK]

Common Mistakes:

• Using TCP or HTTP instead of UDP for UDP connection
• Confusing serial port syntax with UDP
• Missing the 'udp:' prefix

3.

What will the following code print if the drone sends a heartbeat message?

from pymavlink import mavutil

conn = mavutil.mavlink_connection('udp:127.0.0.1:14550')
msg = conn.recv_match(type='HEARTBEAT', blocking=True)
print(msg.get_type())

medium

A. HEARTBEAT_MESSAGE

B. None

C. HEARTBEAT

D. ERROR

Solution

1. Step 1: Understand recv_match with type='HEARTBEAT'

   The code waits (blocking=True) until it receives a heartbeat message from the drone.

2. Step 2: Check what get_type() returns

   The get_type() method returns the message type as a string, which will be 'HEARTBEAT' for heartbeat messages.

3. Final Answer:

   HEARTBEAT -> Option C

4. Quick Check:

   Heartbeat message type = 'HEARTBEAT' [OK]

Hint: recv_match blocks until message type received, get_type returns type name [OK]

Common Mistakes:

• Expecting None if message received
• Confusing message type string with error
• Assuming get_type returns full message object

4.

Identify the error in this code snippet that tries to connect and wait for a heartbeat:

from pymavlink import mavutil

conn = mavutil.mavlink_connection('udp:127.0.0.1:14550')
msg = conn.recv_match(type='heartbeat', blocking=True)
print(msg)

medium

A. recv_match does not support blocking=True

B. The message type string should be uppercase 'HEARTBEAT'

C. The connection string is missing the port number

D. print(msg) should be print(msg.get_type())

Solution

1. Step 1: Check message type case sensitivity

   MAVLink message types are case sensitive and must be uppercase, so 'heartbeat' is incorrect; it should be 'HEARTBEAT'.

2. Step 2: Verify other parts

   The connection string includes port 14550 correctly; recv_match supports blocking=True; print(msg) is valid to print the message object.

3. Final Answer:

   The message type string should be uppercase 'HEARTBEAT' -> Option B

4. Quick Check:

   Message type strings are uppercase [OK]

Hint: MAVLink message types are uppercase strings [OK]

Common Mistakes:

• Using lowercase message type strings
• Assuming blocking=True is invalid
• Confusing print output with error

5.

You want to write a program that connects to a drone over serial port /dev/ttyUSB0 at 57600 baud, waits for a heartbeat, and then prints "Connected to drone". Which code snippet correctly does this?

hard

A. from pymavlink import mavutil
conn = mavutil.mavlink_connection('serial:/dev/ttyUSB0:57600')
conn.wait_heartbeat()
print('Connected to drone')

B. from pymavlink import mavutil
conn = mavutil.mavlink_connection('udp:/dev/ttyUSB0:57600')
conn.wait_heartbeat()
print('Connected to drone')

C. from pymavlink import mavutil
conn = mavutil.mavlink_connection('serial:/dev/ttyUSB0')
conn.recv_match(type='HEARTBEAT', blocking=False)
print('Connected to drone')

D. from pymavlink import mavutil
conn = mavutil.mavlink_connection('serial:/dev/ttyUSB0:57600')
msg = conn.recv_match(type='heartbeat', blocking=True)
print('Connected to drone')

Solution

1. Step 1: Check connection string format for serial

   The correct format is 'serial:/dev/ttyUSB0:57600' to specify port and baud rate.

2. Step 2: Use wait_heartbeat() to block until heartbeat

   Using conn.wait_heartbeat() waits properly for the heartbeat message before continuing.

3. Step 3: Confirm print statement

   After heartbeat, printing 'Connected to drone' confirms success.

4. Final Answer:

   from pymavlink import mavutil conn = mavutil.mavlink_connection('serial:/dev/ttyUSB0:57600') conn.wait_heartbeat() print('Connected to drone') -> Option A

5. Quick Check:

   Serial connection + wait_heartbeat = correct setup [OK]

Hint: Use wait_heartbeat() after serial connection to confirm link [OK]

Common Mistakes:

• Using UDP instead of serial for serial port
• Using lowercase 'heartbeat' in recv_match
• Not specifying baud rate in connection string