Cross-Validate ArduPilot Telemetry Using MAVLink Inspector

TL;DR: When diagnosing RTL issues in ArduPilot, check for MODE Rsn=2 indicating a radio failsafe, and ensure FS_EKF_ACTION is set correctly, as there is no FS_EKF_ACTION value of 5. Validate telemetry using ERR Subsys=18 for EKF primary changes and ERR Subsys=19 ECode=2 for barometer glitches.

What is MAVLink Inspector?

MAVLink Inspector is a powerful tool for monitoring and validating MAVLink messages in real-time, providing insight into communication between the flight controller and ground control station. It is essential for ensuring the integrity of telemetry data in ArduPilot systems. The key fields in MAVLink messages include:

MSG_ID  TimeUS  Status  Lat  Lng  Alt

• MSG_ID: The unique identifier for each message type.
• TimeUS: The timestamp of the message in microseconds.
• Status: The status of the system or flight mode.
• Lat: Latitude of the vehicle's position.
• Lng: Longitude of the vehicle's position.
• Alt: Altitude above sea level.

Confirming it in Mission Planner

To access MAVLink Inspector in Mission Planner, follow this sequence:

1. Open Mission Planner.
2. Connect to your vehicle.
3. Navigate to the Data tab.
4. Select MAVLink Inspector.

In the MAVLink Inspector window, you can monitor various telemetry parameters. To validate telemetry data, plot the following fields together:

• GPS.Lat and GPS.Lng for position checks.
• BARO.Alt for altitude verification.
• BAT.Curr for battery current analysis.
• ERR.Subsys to identify any error codes.

Confirming it in MAVExplorer

Using MAVExplorer, you can graph telemetry data for deeper analysis. For example:

MAV> graph GPS.Lat GPS.Lng

This command plots the latitude and longitude of the vehicle's position over time, allowing you to visualize any discrepancies in the telemetry data.

Why Synchronization Issues Happen — Ranked by Frequency

1. Incorrect Time Settings: When the system time on ArduPilot does not match the ground control station, it leads to synchronization issues in the telemetry data.
2. Packet Loss: If MAVLink messages are lost during transmission, it can result in gaps in the telemetry data, causing confusion and inaccurate readings.
3. Configuration Errors: Incorrect settings in Mission Planner or QGroundControl may prevent proper data transmission, leading to telemetry inconsistencies.
4. Firmware Versions: Mismatched firmware versions between the flight controller and ground control software can lead to compatibility issues, affecting telemetry reliability.

Fixes for Synchronization Issues

1. Ensure that SYS_TIME is correctly set on both the flight controller and ground control station.
2. Check for any packet loss and adjust the communication settings if necessary.
3. Verify that the MAVLink version used in ArduPilot matches the version in QGroundControl.
4. Update firmware on both the flight controller and ground control station to the latest version.

When This Isn't Actually a Telemetry Issue

• Telemetry may appear incorrect due to physical obstructions affecting GPS signals, leading to inaccurate position data.
• Configuration issues in the ground control software can misrepresent the telemetry data without affecting the actual flight performance.
• Communication issues may arise from poor radio signal strength, which may be confused with telemetry errors.

When LogHat Helps — and When It Doesn't

LogHat enhances telemetry management by providing detailed insights and analysis of flight logs. However, it cannot resolve real-time telemetry synchronization issues; it primarily analyzes historical data. For live troubleshooting, MAVLink Inspector remains the go-to tool.

What is MAVLink Inspector?

A tool for monitoring and validating MAVLink messages in real-time.

How can I fix synchronization issues?

Check the system time settings of your ArduPilot and ground control station.

What are common causes of telemetry errors?

Common causes include incorrect time settings, packet loss, configuration errors, and firmware mismatches.

How do I access MAVLink Inspector in Mission Planner?

Open Mission Planner, connect to your vehicle, go to the Data tab, and select MAVLink Inspector.

What parameters should I plot to validate telemetry?

Plot GPS.Lat, GPS.Lng, BARO.Alt, BAT.Curr, and ERR.Subsys.

To further enhance your telemetry analysis and ensure accurate flight data management, explore the capabilities of LogHat. By integrating advanced analytics, you can streamline your flight operations and gain deeper insights into your drone's performance.