Using Mission Planner
...
Connect your aircraft to the ground station computer using a micro USB cable
Launch the Mission Planner Program
Open the Mission Planner’s Planner Flight Data screen
Select the “DataFlash Logs” tab on the
Click the “Download DataFlash Log Via Mavlink” button
...
Select the log(s) you want to download from the left pane of the popup window
Click “Download Selected Logs”
Wait for the log files to download
...
This will save that log to your MissionPlanner/logs directory, in a folder named after the vehicle type, such as
...
OCTOCOPTER.