Logs and Fault Analysis

By default the aircraft creates a dataflash log on the SD card as soon as it arms. Download it after the flight, or read the card directly.

TIP

Dataflash logs open in Mission Planner, MAVExplorer, the ArduPilot web tools or the PID review tool. They are the aircraft's black box: post-flight fault analysis, flight performance checks and PID tuning all come from them.

NOTE

To log from power-on while you are debugging, set LOG_DISARMED to 1. For a first flight or for PID analysis, set up logging for tuning first.

Logging parameters

Parameter	What it does	Values
LOG_BACKEND_TYPE	Where logs are stored or streamed (bitmask, can be combined)	0: disabled; 1: SD card (the usual choice); 2: MAVLink streaming (needs 921600 baud); 4: onboard dataflash (on boards that have it)
LOG_BITMASK	What gets logged, and therefore how detailed and how big the file is	0: disabled; default: core data kept; other values: set per aircraft type, dropping what you do not need to keep files small
LOG_DISARMED	Logging behaviour while disarmed	0: log only after arming; 1: log from power-on (for debugging); 2: log when not powered over USB; 3: delete logs from unarmed sessions
LOG_FILE_DSRMROT	Log file rotation, to split multi-stage flights	Non-zero: disarm, 15 s, re-arm forces a new file; 0: default, one file per power cycle
LOG_FILE_MB_FREE	Minimum free space kept on the storage medium	Default 500 MB; when space runs short the oldest logs are deleted
LOG_FILE_RATEMAX	Caps the streaming log write rate, which controls file size	Default 0 (no limit); the rate depends on SCHED_LOOP_RATE; related: LOG_BLK_RATEMAX (block logging) and LOG_MAV_RATEMAX (MAVLink logging)
LOG_MAX_FILES	Maximum number of log files, wrapping round	1~500; once full, new logs overwrite the oldest

Downloading flash logs

• Connect the aircraft to the ground station over USB.
• Open Mission Planner's Flight Data screen.
• Click the DataFlash Logs tab at the bottom left and press Download DataFlash Log Via Mavlink.
• Pick the logs to download. They land in the MissionPlanner/logs folder, sorted by aircraft type (a QUADCOPTER folder, for example).

What gets logged

LOG_BITMASK controls which message types are logged; the bit definitions differ between vehicle types. This is the Copter bitmask:

Bit	Bitmask name	What is logged when set
0	Fast Attitude	Attitude at SCHED_LOOP_RATE; required for PID review
1	Medium Attitude	Attitude at 10 Hz
2	GPS	GPS data
3	System Performance	CPU and other performance data
4	Control Tuning	Control data
5	Navigation Tuning	Navigation data
6	RC Input	Transmitter input
7	IMU	IMU (accelerometer and gyro) data
8	Mission Commands	Mission and GCS commands
9	Battery Monitor	Battery data
10	RC Output	Servo output
11	Optical Flow	Optical flow data
12	PID	PID controller data; required for PID review
13	Compass	Compass data
15	Camera	Camera data
17	Motors	Motor data
19	Raw IMU	Raw, unprocessed IMU data
20	Video Stabilization	Attitude at SCHED_LOOP_RATE
21	Fast harmonic notch	Fast harmonic notch data

NOTE

The ATTITUDE message is logged at the highest rate among the options you selected. EKF3 logging is controlled separately by EK3_LOG_LEVEL.

Replaying logs

These four tools replay and analyse logs:

• Mission Planner
• ArduPilot web tools
• MAVExplorer
• PID review tool