Practice - 5 Tasks

Answer the questions below

1fill in blank

easy

Complete the code to define the MAVLink message ID.

Drone Programming

message_id = [1]

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

A0x10

B0xFF

C0x01

D0x00

Attempts:

3 left

💡 Hint

Common Mistakes

Using decimal numbers instead of hexadecimal.

Using an invalid message ID.

✗ Incorrect

The message ID uniquely identifies the MAVLink message type. Here, 0x10 is a common example ID.

2fill in blank

medium

Complete the code to set the payload length of the MAVLink message.

Drone Programming

payload_length = [1]

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

A12

C255

Attempts:

3 left

💡 Hint

Common Mistakes

Setting payload length to zero.

Using too large a number for payload length.

✗ Incorrect

The payload length defines how many bytes the message payload contains. 8 bytes is a common payload size.

3fill in blank

hard

Fix the error in the code to correctly calculate the checksum of the MAVLink message.

Drone Programming

checksum = crc_accumulate([1], message_bytes)

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

A0xFF

B0x00

C0x55

D0xFFFF

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero as initial CRC value.

Using 0xFFFF which is too large for 8-bit CRC.

✗ Incorrect

The checksum calculation starts with 0x00 as the initial CRC value in MAVLink protocol.

4fill in blank

hard

Fill both blanks to create a MAVLink message header with start byte and system ID.

Drone Programming

header = [[1], [2]]

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

A0xFE

B0x01

C0x10

D0x00

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong start byte.

Confusing system ID with message ID.

✗ Incorrect

The start byte for MAVLink v1 is 0xFE and system ID is often 0x01 for the drone.

5fill in blank

hard

Fill all three blanks to build a MAVLink message dictionary with keys: 'msg_id', 'length', and 'payload'.

Drone Programming

mavlink_msg = {'msg_id': [1], 'length': [2], 'payload': [3]

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

A0x10

Cb'\x01\x02\x03\x04\x05\x06\x07\x08'

Db'\x00\x00\x00\x00'

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching payload length and actual bytes.

Using string instead of bytes for payload.

✗ Incorrect

This dictionary represents a MAVLink message with ID 0x10, payload length 8, and an 8-byte payload.

Practice

(1/5)

1. Which part of a MAVLink message contains the actual data being sent between drone and controller?

easy

A. Payload

B. Header

C. Checksum

D. Footer

Solution

Step 1: Understand MAVLink message parts
A MAVLink message has a header, payload, and checksum. The header contains metadata, the payload contains the actual data, and the checksum verifies integrity.
Step 2: Identify the data container
The payload is the part that carries the actual information or data sent between devices.
Final Answer:
Payload -> Option A
Quick Check:
Payload = Data part [OK]

Hint: Payload always holds the message data [OK]

Common Mistakes:

Confusing header with data
Thinking checksum holds data
Assuming footer exists in MAVLink

2. Which of the following is the correct order of parts in a MAVLink message?

easy

A. Header, Payload, Checksum

B. Payload, Header, Checksum

C. Checksum, Header, Payload

D. Header, Checksum, Payload

Solution

Step 1: Recall MAVLink message format
The MAVLink message starts with a header that describes the message, followed by the payload which contains the data, and ends with a checksum to verify message integrity.
Step 2: Match the correct sequence
The correct sequence is Header first, then Payload, and finally Checksum.
Final Answer:
Header, Payload, Checksum -> Option A
Quick Check:
Order = Header -> Payload -> Checksum [OK]

Hint: Header always comes before payload and checksum [OK]

Common Mistakes:

Swapping payload and header order
Placing checksum before payload
Assuming checksum is in the middle

3. Given this simplified MAVLink message structure in code:

message = {"header": {"msg_id": 24}, "payload": {"lat": 12345678, "lon": 87654321}, "checksum": 0xABCD}

What is the value of message["payload"]["lon"]?

medium

A. 0xABCD

B. 12345678

C. 87654321

D. 24

Solution

Step 1: Locate the payload dictionary
The message dictionary has a key "payload" which itself is a dictionary containing "lat" and "lon" keys.
Step 2: Access the longitude value
Accessing message["payload"]["lon"] retrieves the value associated with "lon" inside the payload, which is 87654321.
Final Answer:
87654321 -> Option C
Quick Check:
payload["lon"] = 87654321 [OK]

Hint: Payload keys hold data values, access with payload[key] [OK]

Common Mistakes:

Accessing header instead of payload
Confusing checksum with data
Using wrong key names

4. Identify the error in this MAVLink message snippet:

msg = {"header": {"msg_id": 30}, "payload": {"alt": 500}, "checksum": "1234"}

Assuming checksum must be an integer, what is wrong?

medium

A. Payload key 'alt' is missing

B. Checksum is a string, should be an integer

C. Header missing 'msg_id'

D. Payload should be a string, not a dictionary

Solution

Step 1: Check checksum data type
The checksum is given as a string "1234" but it should be an integer value for proper validation.
Step 2: Verify other parts
The header has a valid "msg_id" and payload has the "alt" key correctly as a dictionary, so no issues there.
Final Answer:
Checksum is a string, should be an integer -> Option B
Quick Check:
Checksum type must be integer [OK]

Hint: Checksum must be numeric, not string [OK]

Common Mistakes:

Ignoring checksum type
Assuming payload keys missing
Confusing header fields

5. You want to create a MAVLink message that sends GPS coordinates with latitude and longitude. Which structure correctly represents this message including header, payload, and checksum?

hard

A. {"header": {"msg_id": 33}, "payload": "lat=34567890, lon=98765432", "checksum": 0x1A2B}

B. {"payload": {"lat": 34567890, "lon": 98765432}, "header": {"msg_id": 33}, "checksum": 0x1A2B}

C. {"header": {"msg_id": 33}, "payload": {"lat": "34567890", "lon": "98765432"}, "checksum": "0x1A2B"}

D. {"header": {"msg_id": 33}, "payload": {"lat": 34567890, "lon": 98765432}, "checksum": 0x1A2B}

Solution

Step 1: Check message part order and types
{"header": {"msg_id": 33}, "payload": {"lat": 34567890, "lon": 98765432}, "checksum": 0x1A2B} has the correct order: header, payload as a dictionary with numeric lat/lon, and checksum as a hex integer.
Step 2: Identify errors in other options
{"payload": {"lat": 34567890, "lon": 98765432}, "header": {"msg_id": 33}, "checksum": 0x1A2B} has wrong order (payload before header). {"header": {"msg_id": 33}, "payload": "lat=34567890, lon=98765432", "checksum": 0x1A2B} uses payload as a string, not dictionary. {"header": {"msg_id": 33}, "payload": {"lat": "34567890", "lon": "98765432"}, "checksum": "0x1A2B"} uses strings for lat/lon and checksum, which is incorrect.
Final Answer:
Correct structure with header, numeric payload, and integer checksum -> Option D
Quick Check:
Correct order and types = {"header": {"msg_id": 33}, "payload": {"lat": 34567890, "lon": 98765432}, "checksum": 0x1A2B} [OK]

Hint: Header first, payload dict with numbers, checksum integer [OK]

Common Mistakes:

Wrong order of parts
Payload as string instead of dict
Checksum as string instead of int

MAVLink message structure in Drone Programming - Interactive Code Practice

Start learning this pattern below

Practice

Solution

Step 1: Understand MAVLink message parts

Step 2: Identify the data container

Final Answer:

Quick Check:

Solution

Step 1: Recall MAVLink message format

Step 2: Match the correct sequence

Final Answer:

Quick Check:

Solution

Step 1: Locate the payload dictionary

Step 2: Access the longitude value

Final Answer:

Quick Check:

Solution

Step 1: Check checksum data type

Step 2: Verify other parts

Final Answer:

Quick Check:

Solution

Step 1: Check message part order and types

Step 2: Identify errors in other options

Final Answer:

Quick Check: