Analyze Drone Flight Logs with Python on a Pi

Every ArduPilot flight records hundreds of values per second. pymavlink can read those logs, and matplotlib turns them into charts that reveal vibration, voltage sag and tuning problems.

Mission steps

1. Download the log

   Copy the .bin file from the flight controller's SD card or download it with Mission Planner or QGroundControl.

2. Install tools

   pip install pymavlink matplotlib in a virtual environment.

3. Read messages

   The script extracts barometer altitude and battery voltage over time.

4. Plot and compare

   Look for voltage drops on punch-outs and altitude wobble that signals tuning or vibration issues.

5. Check vibration

   Plot VIBE messages; values consistently above about 30 m/s² usually mean you need better motor or FC soft-mounting.

Code

from pymavlink import mavutil
import matplotlib.pyplot as plt

log = mavutil.mavlink_connection('flight.bin')
t, alt, tv, volt = [], [], [], []
while True:
    m = log.recv_match(type=['BARO', 'BAT'])
    if m is None: break
    if m.get_type() == 'BARO': t.append(m.TimeUS / 1e6); alt.append(m.Alt)
    else: tv.append(m.TimeUS / 1e6); volt.append(m.Volt)

fig, ax = plt.subplots(2, 1, sharex=True)
ax[0].plot(t, alt); ax[0].set_ylabel('Altitude m')
ax[1].plot(tv, volt, color='orange'); ax[1].set_ylabel('Battery V')
plt.savefig('flight.png')

Tip: test every script on the bench before installing it in a moving machine.

Questions