What is MAVLink COMMAND_LONG: Explanation and Example

The COMMAND_LONG message in MAVLink is a flexible command format used to send instructions to drones or autopilots with up to seven parameters. It acts like a universal remote control command that can carry different types of commands by specifying a command ID and parameters.

How It Works

The COMMAND_LONG message works like sending a detailed instruction to a drone. Imagine you want to tell a robot to do something specific, like move to a point, change speed, or start a camera. Instead of having a separate message for each action, COMMAND_LONG uses one message format with a command ID and up to seven parameters to cover many commands.

Each command ID corresponds to a specific action the drone understands. The parameters provide extra details, like coordinates or speed values. This makes COMMAND_LONG very flexible, like a Swiss Army knife for drone commands.

Example

This example shows how to create and send a COMMAND_LONG message to command a drone to take off using Python with pymavlink.

python

from pymavlink import mavutil

# Connect to the drone (replace with your connection string)
master = mavutil.mavlink_connection('udp:127.0.0.1:14550')

# Wait for the heartbeat message to find the system ID
master.wait_heartbeat()

# Define the command: MAV_CMD_NAV_TAKEOFF (22)
command = 22
param1 = 0  # Minimum pitch
param2 = 0  # Empty
param3 = 0  # Empty
param4 = 0  # Yaw angle
param5 = 0  # Latitude (use current)
param6 = 0  # Longitude (use current)
param7 = 10 # Altitude to take off to (meters)

# Send COMMAND_LONG message
master.mav.command_long_send(
    master.target_system,    # Target system ID
    master.target_component, # Target component ID
    command,                 # Command ID
    0,                       # Confirmation
    param1, param2, param3, param4, param5, param6, param7
)

print('Takeoff command sent')

Output

Takeoff command sent

When to Use

Use COMMAND_LONG when you need to send specific commands to a drone that require parameters, such as takeoff, land, change speed, or start a mission. It is ideal for controlling drones remotely with detailed instructions.

For example, a ground control station uses COMMAND_LONG to tell a drone to take off to a certain altitude or to return home. Developers use it when building custom drone applications that need precise control commands.

Key Points

• COMMAND_LONG is a versatile MAVLink message for sending commands with parameters.
• It supports up to seven parameters to customize the command.
• Each command has a unique ID that tells the drone what action to perform.
• Commonly used for actions like takeoff, land, and mission control.
• Works as a universal command format in drone communication.

Key Takeaways

COMMAND_LONG sends flexible commands with up to seven parameters to drones.

It uses a command ID to specify the action the drone should perform.

Ideal for remote control tasks like takeoff, landing, and mission commands.

Widely used in ground control software and drone programming.

Allows detailed instructions in a single message format.