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RevGeo Multipurpose Puzzle B ox. Dan Chambers, Josh Marchi, Jeff King, Paul Rosenberger. Overview. “Reverse Geocache ” Box Locked box that will only open after one or more pre-determined GPS locations have been visited
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RevGeoMultipurpose Puzzle Box Dan Chambers, Josh Marchi, Jeff King, Paul Rosenberger
Overview • “Reverse Geocache” Box • Locked box that will only open after one or more pre-determined GPS locations have been visited • Directs user to next location by GPS coordinates or text displayed on LCD, or by an LED compass • Route stored on microSD card located inside the box, able to be reprogrammed by PC • RFID “master key” to allow access to box without finishing puzzle
PSSCs • An ability to obtain and decode global positioning data in order to verify if current location matches pre-determined desired location. • An ability to utilize accelerometerand magnetometer data to determine a compass heading with tilt compensation. • An ability to access and interpret files located on a microSD card. • An ability to display information to the user via an LCD display. • An ability to identify an RFID tag using an RFID reader.
Major Design Constraints • Computation • GPS Coordinate analysis, tilt compensation calculations • Communication • Interact with GPS, RFID, Compass, LCD in a timely fashion • Battery Powered Device • Low power usage / rechargeable battery • Packaging • Compact, “personal-sized” box
Computational Requirements • Compass heading / tilt compensation (polled) • Floating point values, trig functions required (lookup table) • GPS coordinate analysis (1Hz) • Distance from target • SD card file system, interface library • Large amount of Flash/SRAM
Interface Requirements • Receive data from a variety of sensors/modules • GPS, RFID, Accelerometer/Magnetometer • Read data from MicroSD card • Output audio to speaker • Control servo locking mechanism • LCD Display • Parallel GPIO / shift register (6 - 12 GPIO pins) • LED compass ring • Shift registers (2 GPIO pins) • 1-2 Pushbuttons (GPIO)
On-Chip Peripheral Requirements • 3 UART Modules • GPS, RFID, Debug • 1 SPI Module • MicroSD interface • 1 I2C Module • Accelerometer / Magnetometer • 2 PWM Channels • Speaker, Servo Control • 2+ Output Compare Timer Channels • Compass polling, LCD strobe
Component SelectionMicrocontroller • PIC24FJ256GA106 • 16 Bit Architecture • 16 MIPS CPU speed • 256KB Flash • 16KB RAM • Memory Disk Drive File System Library Support • 4 UART Modules • 3 I2C Modules • 3 SPI Modules • 64 Total Pins
Off-Chip Peripheral Requirements • GPS Module • RFID Receiver • Digital Compass • Accelerometer/Magnetometer • Serial to USB Bridge • Debug
Component SelectionGPS Receiver • Trimble Copernicus II • Time to first lock: 38 sec • Dual serial ports • Reconfigurable UART rates • Position Accuracy: <2.5 m 50%, <5 m 90%
Component SelectionDigital Compass • LSM303DLH • +- 2/4/8 g Accelerometer • +-1.3 to +- 8.1 gauss Magnetometer • I2C Serial Out • Excellent application notes for tilt compensation
Power Constraints • Battery powered device • Lithium-Ion Polymer single cell battery (3.7 VDC) • 3300 mAh • Multiple operating voltages • Micro, GPS, MicroSD, Compass (3.3V) • LCD, RFID (5V) • Two converters be used to regulate both voltage levels. • Must be rechargable • MAX1555 USB battery charger IC will be used • Allows charging through USB or additional DC source
Packaging Constraints • Highly durable • Easy to carry • Relatively small in size • Should be able to receive GPS signal from within the box through an antenna • Pelican 1150 Case • Inside dimensions 8-3/8" x 5-7/8" x 3-11/16" • Outsidedimensions 9-1/4" x 7-9/16" x 4-3/8" • LidDepth 3/4"
Cost Constraints • Most expensive: GPS receiver - $80 • RFID kit - $50 • Digital Compass - $30 • GPS, RFID, and Compass initially include breakout boards, which increase their cost • Box should not exceed $300 • Box made without breakout boards would cost less than $225