User guide

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© 2009 Microsoft Corporation, all rights reserved.
SenseCam v2.3 User Guide Page 29 of 31 10/03/2009
6. SenseCam hardware details
6.1. Hardware components
The SenseCam is built around a PIC 18F8722 6 MIPS microcontroller with 128KB of flash
memory, 4KB RAM, copious general purpose I/O (GPIO) lines and several on-chip
peripherals including PWM, UART, I
2
C and SPI.
Figure 20 lists the major components in addition to the PIC along with their basic
specifications and method of interface. USB connectivity is achieved using a non-standard
approach – the SD card is actually multiplexed between the PIC microcontroller (which is
selected when the SenseCam is recording data) and an off-the-shelf USB-to-SD card
interface chip (which is selected when a USB connection is detected). This allows us to
support high speed USB 2.0 operation, which allows data to be transferred at approximately
4MB/s (around 175 images per second, or 10,000 per minute). Figure 21 shows the basic
architecture of the SenseCam. Figure 22 depicts the front and the back of the SenseCam
PCB, highlighting the main hardware components.
Component
Part number
Specification
Interface
Flash memory
Standard SD card
To 2GB (1GB standard)
SPI
Camera module
CoMedia C328-7640
VGA (onboard JPEG compression)
UART
Camera lens
Marshall Electronics V-
4301.9-2.0FT-IRC
119º (diag) wide-angle lens w/ IR filter
n/a
Accelerometer
Kionix KXP84
Tri-axis
I
2
C
Temperature
Nat Semi LM75
Range -55 to +125ºC, ±2ºC
I
2
C
Real-time clock
Maxim/Dallas DS1340
I
2
C
Light level
TAOS TCS230
RGB intensity
PWM
Passive IR (PIR)
Seiko SKP-MS401
Miniature form factor
GPIO
Push buttons
Omron B3F-3150
GPIO
Sounder
Murata PKLCS1212
PWM
Audio recording
4
Oki MS87V1021
2Mb DRAM for 60s audio at 8ksps
SPI
GPS
5
n/a
External GPS unit
BT
Figure 20: The main peripherals (including all sensors) in the v2.3 SenseCam, with a summary of
their specification and the method of interface to the PIC microcontroller.
4
Audio recording is still under development.
5
GPS information from a standalone Bluetooth GPS receiver can be logged by the SenseCam using
the Bluetooth plug-in unit.