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SenseCam v2.3 User Guide Page 21 of 31 10/03/2009

5. SenseCam file formats

5.1. Volume label

The SenseCam volume label will be of the form “MSRC_SC xxx” where xxx is the serial

number of the particular camera. If the volume label is changed manually it will be reset

when the SenseCam next boots up (following a hard power cycle or a USB disconnect),

unless the volume label is deleted (in which case no new volume label will be created).

5.2. File system structure

The root directory on the SenseCam file system typically contains four sub-directories:

DATA, SYSTEM, PCVIEWER and DOCS. The latter two folders are simply used as

convenient places to store copies of the MSRC viewer software and SenseCam

documentation. Their presence (or absence) has no bearing on the operation of the

SenseCam. Indeed, it is possible to use the SenseCam as a general-purpose external USB

disk. Note that the SenseCam firmware does not support long filenames.

The SYSTEM directory contains system files, most notably BOOT.BAT – a script file that

is executed each time the SenseCam boots up (following a hard power cycle or a USB

disconnect). The various BOOT.BAT options are detailed below in Section 5.4. The

SYSTEM directory also contains various .CSV format files that may be used to set the real-

time clock on the SenseCam. These are also detailed below.

The DATA directory contains all the image and sensor data recorded by the SenseCam.

Sensor data is recorded in a single .CSV file called SENSOR.CSV, described fully in

Section 5.5. An image counter internal to the SenseCam (which is cached in non-volatile

memory) records how many images have been captured in the lifetime of the device. Images

are stored as individual .JPG files with a numeric filename based on the value of the image

counter. These image files are stored within a hierarchy of directories. For example, image

number 00010297.JPG is stored in a directory named „M0102‟ which itself is in a directory

named „H01‟ within the \DATA directory. This multi-level structure, with High level

directories named according to the most significant two digits of the six-digit image counter

and Medium level directories named according to the most significant four digits of the six-

digit image counter limits the number of entries in each directory to around 100. This is

important because it reduces the time required for creating and accessing files – with the

limited resources of the SenseCam microcontroller the linear search through a directory

cluster chain can be quite time consuming.

If a manual capture is requested (via the manual shutter button) whilst a sensor-triggered

image capture is already in progress, the image file currently being written is aborted, the

image counter is incremented and a new image file is created. In order to prevent the

aborted image from being mistaken for a valid .JPG file (it will actually be the first part of

an incomplete .JPG file) it is renamed with the extension .ABO (for ABOrted).

5.3. Format of the SENSOR.CSV file

The sensor data is stored in a simple comma separated value (.CSV) file, where every line

represents one piece of sensor (or other) data. Lines are <CR><LF> separated. Every line

entry starts with a 3-letter code indicating what that line represents. If the SENSOR.CSV

file does not exist (for example if it has been deleted following sensor data import using the

SenseCam Image Importer) it will be recreated. If it does exist it will be appended to.