Using MAVLink Inspector to Validate ArduPilot Telemetry Effectively

TL;DR: To validate ArduPilot telemetry effectively, use the ERR Subsys=19 ECode=0 to identify barometer-related issues, and implement BATT_LOW_VOLT = 3.5 to ensure battery failsafe triggers before critical levels. The MAVLink Inspector tool aids in real-time telemetry analysis, providing insights into your drone's flight performance.

How Can You Use MAVLink Inspector to Validate ArduPilot Telemetry Effectively?

Understanding MAVLink Inspector is key to effective telemetry validation.

The MAVLink Inspector is a tool used to monitor and analyze MAVLink traffic in real-time, providing crucial information about telemetry data during flight. It helps engineers validate the accuracy of telemetry data from ArduPilot, allowing for effective adjustments to enhance drone performance. The key log message fields associated with MAVLink Inspector include:

MAVLink Inspector
TimeUS
MsgType
SystemID
ComponentID
Seq

• TimeUS: Timestamp of the message in microseconds since boot.
• MsgType: Type of MAVLink message being sent.
• SystemID: Identifier for the system sending the message.
• ComponentID: Identifier for the component sending the message.
• Seq: Sequence number of the message for tracking.

Confirming It in Mission Planner

Accessing MAVLink Inspector in Mission Planner is straightforward.

To access and use the MAVLink Inspector in Mission Planner, follow this click-path:

1. Open Mission Planner.
2. Connect to your drone.
3. Go to the Flight Data tab.
4. Press Ctrl + F to open the MAVLink Inspector.

Within the MAVLink Inspector, you can plot several fields to analyze telemetry data. Recommended fields to plot together include:

• GPS.Status
• BAT.Voltage
• ERR.Subsys
• CTUN.Alt
• CTUN.ThO

Confirming It in MAVExplorer

MAVExplorer offers another layer of telemetry analysis.

In MAVExplorer, you can also analyze telemetry data with the following command:

MAV> graph CTUN.Alt GPS.Status

This command plots the altitude from the CTUN message against the GPS status. By analyzing this plot, you can determine if the altitude data is reliable and whether the drone is achieving a 3D fix. A reliable 3D fix is indicated by GPS.Status values of 6 or higher.

Why MAVLink Inspector Issues Happen — Ranked by What We See Most Often

Identifying common MAVLink Inspector issues is essential for troubleshooting.

1. GPS Glitches: Indicated by GPS.Status values below 6, which prevent reliable positioning and can lead to unexpected RTL behavior.
2. Barometer Glitches: Noted by ERR Subsys=19 ECode=0, indicating that the barometer is functioning correctly, which impacts altitude readings.
3. Throttle Failsafe: Triggered by ERR Subsys=25 ECode=0, indicating that a potential thrust loss has not been detected, affecting the drone's ability to maintain altitude.
4. EKF Check Failures: Identified by ERR Subsys=3 ECode=0, signaling that the EKF is functioning well, which can lead to stable flight.
5. Battery Voltage Drop: Observed when BAT.Voltage falls below 3.3V, which may not trigger a failsafe but can lead to performance degradation.

Fixes for Common MAVLink Inspector Issues

Implementing these fixes can address common telemetry issues.

1. Set BATT_LOW_VOLT = 3.5 to ensure a failsafe triggers before the battery drops to critical levels.
2. Monitor ERR Subsys=19 and implement routine maintenance on the barometer to prevent glitches.
3. Increase the GPS_HDOP_GOOD = 1.0 threshold to ensure reliable positioning from GPS signals.
4. Regularly inspect telemetry logs to identify patterns in ERR messages for proactive adjustments.

When This Isn't Actually MAVLink Inspector Issues

Understanding other factors is key to effective troubleshooting.

• Low battery conditions may appear similar but are often indicated by voltage drops rather than telemetry errors.
• GPS status fluctuations can be mistaken for EKF issues; however, they may arise from environmental factors or hardware limitations.
• Barometer errors are not always related to MAVLink Inspector. They may stem from physical obstructions affecting pressure readings.
• Telemetry data may simply be lagging due to poor communication rather than an underlying issue with the drone's systems.

When LogHat Helps — and When It Doesn't

LogHat can provide insights but has limitations compared to real-time tools.

LogHat provides in-depth analysis of telemetry data, pinpointing issues like EKF failures and GPS glitches effectively. However, it does not replace the need for real-time monitoring tools like MAVLink Inspector, as it relies on historical data rather than live telemetry streams.

What is MAVLink Inspector?

A tool that provides real-time information on MAVLink traffic for telemetry validation.

How can I access MAVLink Inspector?

You can access it via Mission Planner by pressing Ctrl-F or through QGroundControl.

What are common issues identified by MAVLink Inspector?

Common issues include GPS glitches, barometer glitches, and EKF check failures.

How can I improve my drone's telemetry performance?

Adjust parameters like BATT_LOW_VOLT for better performance.

What should I monitor in my telemetry logs?

Monitor fields like GPS.Status, BAT.Voltage, and ERR.Subsys for insights.

What does ERR Subsys=19 ECode=0 indicate?

It indicates that the barometer is functioning correctly, impacting altitude readings.

How does LogHat assist in telemetry analysis?

LogHat analyzes historical telemetry data to identify patterns and issues for better flight planning.