Logs Analysis

The 305ap writes three kinds of logs: flight logs (ULog) on the SD card, crash logs after a hard fault, and the boot log (the console messages since power-up).

Flight Logs

PX4 writes flight logs as .ulg files in /fs/microsd/log/.

Parameter	Default	Meaning
SDLOG_MODE	0	When to log: 0 arm to disarm, 1 boot to disarm, 2 boot to shutdown
SDLOG_PROFILE	Default set	What to log; add profiles for tuning or system identification

Set SDLOG_MODE = 1 to capture problems that happen before arming, such as sensor or GPS issues on the bench.

Downloading

• QGroundControl: Analyze Tools → Log Download, select logs, Download. Over USB this is quick; over a telemetry radio it is slow.
• SD card: remove the card and copy the log folder on a PC.

Analysing

Tool	Use
Flight Review	Upload a log for standard plots: attitude tracking, vibration, power, GPS, estimator status
PlotJuggler	Any topic, with your own plots; good for comparing signals
pyulog	Command-line and Python access (ulog_info, ulog2csv)

What to Check First

• Vibration: accelerometer vibration in the green range. If high, check the rubber isolators and propeller balance.
• Rate tracking: angular rate setpoint vs. estimate on each axis.
• Power: battery voltage sag under throttle. Current is only logged with an external current sensor.
• Estimator: EKF2 innovation test ratios below 1. Persistent high values point at a sensor problem.
• Magnetometer: field strength over the flight. If it changes with throttle or when a 5 V device switches, the compass is picking up current; see Magnetometer.
• GPS: satellites used, horizontal accuracy (eph), and fix type.

Crash Logs

If the firmware hits a hard fault, the board saves the fault details (registers, stack, task) to backup SRAM, which survives a reset but not a power-off, and resets. On the next boot PX4 writes them to the SD card as:

/fs/microsd/fault_<date>_<time>.log

The date comes from the board's clock, which may be wrong if it has had no GPS fix since power-up.

Useful commands in the MAVLink Console:

hardfault_log check     # is there a fault not yet written to the SD card?
hardfault_log commit    # write it to the SD card now
ls /fs/microsd          # list fault files

When reporting a crash, include the fault_*.log file, the flight log, and the firmware version (ver all).

note

Firmware before 20261019b could stop at boot after a hard fault, waiting at a console prompt that the board can't answer, until power was removed. That also lost the crash log. Update to 20261019b or later.

Boot Log

dmesg in the MAVLink Console prints the messages since power-up: firmware version, sensors found, and any startup errors.

dmesg

Hardware Console

The same messages, including crash dumps, are also sent out of the VTX connector, pin 5 (VTX_SBUS, USART3 TX), at 57600 baud, 8N1. This works even when USB is not available, which makes it the best way to see what happens during a reset.

1. Connect a 3.3 V USB-to-serial adapter: adapter RX to VTX pin 5, adapter GND to VTX pin 4 or 6.
2. Open the port at 57600 baud (for example picocom -b 57600 /dev/ttyUSB0).
3. Power the board.

The console is output-only on the 305ap: there is no console input pin.