User guide

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© 2009 Microsoft Corporation, all rights reserved.
SenseCam v2.3 User Guide Page 22 of 31 10/03/2009
With sensor readings, the 3-letter sensor code is followed by the time that the reading was
taken in hours (24 hour clock), minutes and seconds, and then followed by the value of the
reading. Since each sensor entry only logs the time of the reading, we periodically (every
hour in the latest firmware) log the time and date. In addition to environmental sensing, we
also periodically check and log the internal battery terminal voltage. Whenever an image is
captured, the time of capture and the filename used to store the image are recorded in the log
file, along with a one-character „reason‟ code (why the SenseCam took a photo at that time).
When the camera boots up from cold, or is USB sync‟ed or unsync‟ed , it adds three entries
to the sensor log file which indicate the time, date and build directory for the firmware, the
version of the firmware, and various bits of system information.
Temperature data is represented by a 9-bit, two‟s
complement word with an LSB (least significant
bit) equal to 0.5°C. For positive temperature
readings simply divide by two to convert to
centigrade. The table in Figure 14 opposite gives
some example conversions.
Figure 14: Example temperature readings and the
corresponding SENSOR.CSV values.
VER,2,6,6
FIL,C:\Development\SenseCam\firmware\PIC\main_v22.c,10:52:21,16-May-06
SYS,00000167,0x00,0x03,0x1f,0xff
RTC,2006,06,19,12,28,02
ACC,12,28,07,00034,00848,00036
TMP,12,28,07,00047
CLR,12,28,07,03756
PIR,12,28,07,1
BAT,12,28,07,41821
CAM,12,28,11,00000230.JPG,M
...
Figure 15: Example SENSOR.CSV file entries.
Temperature
Binary
Hex
+125°C
0 1111 1010
0FAh
+25°C
0 0011 0010
032h
+0.5°C
0 0000 0001
001h
0°C
0 0000 0000
000h
−0.5°C
1 1111 1111
1FFh
−25°C
1 1100 1110
1CEh
−55°C
1 1001 0010
192h