Sending custom MAVLink commands in Drone Programming - Step-by-Step Execution

Concept Flow - Sending custom MAVLink commands

Start

↓

Create MAVLink command message

↓

Set command parameters

↓

Send command to drone

↓

Drone receives and processes command

↓

Receive acknowledgment

↓

Check if command succeeded?

No→Handle error

Yes↓

End

This flow shows how to build, send, and confirm a custom MAVLink command to a drone.

Execution Sample

Drone Programming

msg = create_mavlink_command(command_id=300, param1=1.0)
send_command(msg)
ack = receive_ack()
if ack.success:
    print('Command succeeded')
else:
    print('Command failed')

This code creates a custom MAVLink command, sends it, waits for acknowledgment, and prints success or failure.

Execution Table

Step	Action	Command Parameters	Drone Response	Output
1	Create command message	command_id=300, param1=1.0	None	None
2	Send command to drone	command_id=300, param1=1.0	None	None
3	Drone processes command	command_id=300, param1=1.0	Processing	None
4	Receive acknowledgment	None	ack.success=True	None
5	Check acknowledgment	None	ack.success=True	Print 'Command succeeded'

💡 Command acknowledged with success, so execution ends after printing success message.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	Final
msg	None	{command_id:300, param1:1.0}	{command_id:300, param1:1.0}	{command_id:300, param1:1.0}	{command_id:300, param1:1.0}
ack	None	None	None	{success: True}	{success: True}

Key Moments - 3 Insights

Why do we wait for an acknowledgment after sending the command?

Because the drone needs to confirm it received and understood the command. See execution_table step 4 where ack.success is received.

What happens if ack.success is False?

The program would handle the error, possibly retry or alert the user. This is shown in the flow where 'Check if command succeeded?' leads to 'Handle error' if No.

Why do we set parameters like param1 when creating the command?

Parameters tell the drone what exactly to do with the command. Without them, the command might be incomplete or ignored. See execution_table step 1 for parameters.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'ack.success' at step 4?

A None

B False

C True

D Error

💡 Hint

Check the 'Drone Response' column at step 4 in execution_table.

At which step does the drone start processing the command?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the 'Action' column in execution_table for when processing happens.

If the command parameters were missing at step 1, what would likely happen?

A Drone might ignore or error on command

B Drone processes command normally

C Acknowledgment would be success

D Program prints 'Command succeeded'

💡 Hint

Refer to key_moments about why parameters are important.

Concept Snapshot

Sending custom MAVLink commands:
1. Create command message with command ID and parameters.
2. Send command to drone.
3. Wait for acknowledgment.
4. Check if command succeeded.
5. Handle errors if any.
Always set parameters correctly for expected behavior.

Full Transcript

This visual trace shows how to send a custom MAVLink command to a drone. First, the program creates a command message with a specific command ID and parameters. Then it sends this message to the drone. The drone processes the command and sends back an acknowledgment. The program checks if the acknowledgment indicates success. If yes, it prints a success message; if not, it handles the error. Tracking variables like the command message and acknowledgment helps understand the flow. Key points include waiting for acknowledgment to confirm command receipt and setting parameters to define command behavior.