Brick Logger, now with milliseconds

Until now Brick Logger intervals could be defined in seconds. This is okay for slowly changing values such as temperature or humidity. But intervals in seconds might not be small enough for fast changing values as provided by the IMU Brick or Accelerometer Bricket as several users confirmed.

Because of that Brick Logger since version 2.0.2 (Brick Viewer since version 2.3.1) now supports intervals in milliseconds. Matching new time formats with millisecond resolution have been added as well as the option to define a custom time format using strftime syntax.