The G.L.A.I.S. project is
designed to give informational audio tours without defining a predetermined tour
route. G.L.A.I.S. is designed to automatically determine your location via
GPS and play the corresponding information tied to that location. Tourists
can now freely roam an entire outdoor area or even a city at their leisure,
taking in the information they want, at the pace they want.
Features:
·MP3 audio file playback, stop and rewind.
·Tours are stored on Secure Digital Card for
quick swapping tours.
·Backlit LCD screen with varying levels of text
output.
·Runs off a 9 Volt battery with over 4 hours
playtime.
·Simple, User Friendly interface.
Demonstration Video
Usage Description
The
G.L.A.I.S. unit is mostly self sufficient, needing minimal user interaction
to perform it's function. On power up, the unit will display the G.L.A.I.S.
Splash Screen, followed by the main menu, where users can select one of two
modes, Tour mode or Jukebox mode.
Tour mode is the main
function of our project. Once selected, the user is presented with a quick
"how-to" screen before entering full tour mode. In Tour mode, the
unit is fully automated and hand-free. When the user approaches a point of
interest, the audio track corresponding to that unit begins playing. The user
may pause, stop, and resume the tour at anytime using the interface.
Jukebox mode allows the user
to play MP3 tracks from the SD card as if it was a standard music player.
Once selected, the user is presented with a quick "how-to" screen
before entering full tour mode. The user has basic playback and volume controls
while in Jukebox mode, and can exit the mode at any time.
Technical Specifications
·18F8722
PIC Processor
o2 USART ports
o2 MSSP ports (SPI)
o4KB Boot loader memory
o128KB Program memory
·MP3
Decoder
oContains built-in digital-to-analog converter
oDigital volume control
oAccepts all forms of MP3 bit rates, including
variable and average
·GPS
InfoTrac 102C
oAccurate to 6 meters
oDoes not require an external antenna
oCan utilize a battery back up power supply to
maintain signal fix while in power down mode.
·Secure
Digital Card Interface
oSwappable flash memory
oVariable size memory
oCompatible with any computer for downloading
tours.
·Liquid
Crystal Display
o4 lines x 20 character screen
oBack light for easy of use at night.
oLarge text for easy viewing.
Technical Description
G.L.A.I.S.
runs off of a robust 18F8722 PIC processor with a 40 MHz crystal
clock. On power up, the processor will initialize the 4 main
subsystems, LCD, MP3 decoder/player, SD card, and the GPS. The LCD and GPS
run off USART protocols and are initialized by passing strings of characters
across the serial interface at the proper baud rate. Our project has both
units running at 9600 baud and interacting directly with the processor on
separate bus lines, removing possible traffic and congestion issues.
The SD card and GPS both
utilize the SPI protocol. The SD card, however, defaults to it's own
proprietary SD bus mode, and must be 'reset' into SPI mode. SPI protocol also
allows the use for CRC checksums for every block of data sent, which for this
product is ignored. The MP3 chip, on a separate SPI bus, will accept data
whenever it sets it's data request line high to the processor. Both the SD
card and MP3 player are being run as slave units to the processor.
The
Processor is the host for all the subsystems and can run basic C style code.
The processor can handle the basic libraries and also can be expanded to
utilize user-created libraries and functions. An external bootloader and
compiler will translate our C code into machine level language and load it
into program memory.
The SD card uses the FAT16
file system, written by Microsoft. Once the SD card is initialized into SPI
mode, a series of reads are performed to determine the FAT structure on the
card. Once the FAT tables are initialized, a file can be located by it's
short name (8.3 DOS style). Reading the file involves traversing the FAT
table for the linked list of the clusters of the file, which may or may not
be contiguous.
The LCD display has a serial
backpack to allow us to easily send character strings and commands to it via
a serial interface. The state of the LCD can be modified by sending a set of
byte commands, changing the cursor location and shape, or clearing the
screen. The backlight is also controlled in this fashion. Printing a string
to the LCD is as simple as sending the string directly to the port, the
serial backpack parses and sends the characters to the screen.
The GPS sends out a steady
stream of information via the serial USART port. This information is comma
delimited, and a string tokenizer will successfully parse out the useful
information. Once the unit has established at least 3 satellite connections,
the unit will begin sending the proper sting in NMEA standard protocol.
The MP3 player will stream
music files as they are written to the chip. With the external 12 Mhz chip
installed, the decoder is able to decode any MPEG I, II, III files as well as
WMAs and WAVs. The volume is controled through SPI control signals during
playback.
Schematic (click for full image)
Fabricated Board (click for full image)
2006-2007 David Fong, Davis Brimer, Samantha
Alt, Ethan Kravitz, Daniel Popescu
