Dan Chambers, Josh Marchi, Jeff King, Paul Rosenberger

RevGeoMultipurpose Puzzle Box

“Reverse Geocache” BoxLocked 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

Overview

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 accelerometer and 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.

PSSCs

ComputationGPS Coordinate analysis, tilt compensation

calculationsCommunication

Interact with GPS, RFID, Compass, LCD in a timely fashion

Battery Powered DeviceLow power usage / rechargeable battery

PackagingCompact, “personal-sized” box

Major Design Constraints

Compass heading / tilt compensation (polled) Floating point values, trig functions required

(lookup table)GPS coordinate analysis (1Hz)

Distance from targetSD card file system, interface library

Large amount of Flash/SRAM

Computational Requirements

Receive data from a variety of sensors/modulesGPS, RFID, Accelerometer/Magnetometer

Read data from MicroSD cardOutput audio to speakerControl servo locking mechanismLCD Display

Parallel GPIO / shift register (6 - 12 GPIO pins)LED compass ring

Shift registers (2 GPIO pins)1-2 Pushbuttons (GPIO)

Interface Requirements

3 UART ModulesGPS, RFID, Debug

1 SPI ModuleMicroSD interface

1 I2C ModuleAccelerometer / Magnetometer

2 PWM ChannelsSpeaker, Servo Control

2+ Output Compare Timer ChannelsCompass polling, LCD strobe

On-Chip Peripheral Requirements

PIC24FJ256GA10616 Bit Architecture16 MIPS CPU speed256KB Flash16KB RAMMemory Disk Drive File

System Library Support4 UART Modules3 I2C Modules3 SPI Modules64 Total Pins

Component SelectionMicrocontroller

GPS ModuleRFID ReceiverDigital Compass

Accelerometer/MagnetometerSerial to USB Bridge

Debug

Off-Chip Peripheral Requirements

Trimble Copernicus IITime to first lock: 38

secDual serial portsReconfigurable UART

ratesPosition Accuracy: <2.5 m 50%, <5 m 90%

Component SelectionGPS Receiver

LSM303DLH+- 2/4/8 g

Accelerometer+-1.3 to +- 8.1 gauss

MagnetometerI2C Serial OutExcellent application

notes for tilt compensation

Component SelectionDigital Compass

Battery powered deviceLithium-Ion Polymer single cell battery (3.7 VDC)3300 mAh

Multiple operating voltagesMicro, 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 usedAllows charging through USB or additional DC

source

Power Constraints

Highly durableEasy to carryRelatively small in sizeShould be able to receive GPS signal from within

the box through an antenna

Packaging Constraints

• Pelican 1150 Case– Inside dimensions 8-3/8" x 5-7/8" x 3-11/16" – Outside dimensions 9-1/4" x 7-9/16" x 4-3/8"

 – Lid Depth 3/4"

Most expensive: GPS receiver - $80RFID kit - $50 Digital Compass - $30GPS, RFID, and Compass initially include

breakout boards, which increase their costBox should not exceed $300Box made without breakout boards would

cost less than $225

Cost Constraints

Questions?