Download 2/01/2012

Team Scribacious Rabble
Design Constraint Analysis
Paul Rosswurm
Mitch Erdbruegger
Ben Kobin
William Hess
Project Description
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Adaptation of the board game SCRABBLE®
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Maintains the traditional physical tile interface...
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augmented by ..
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Sensing tile location and value
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Automatically calculating and displaying scores
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Maintaining player profiles
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Validating words in the event of a 'challenge'
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Exposing game stats over an external interface
Computational Constraints
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Not much, just pushing data around
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Store player info
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Very Small
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Can be slow
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Simple metrics
Search dictionary for a word
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1 MByte of data
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~200-300 lookups for a binary search
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Can be slow (external EEPROM speed is fine)
Computational Constraints (cont.)
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USB Communications
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USB module or UART w/ external USB logic
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Response latency is not critical
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Not hosting
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Libraries exist (48MHZ, 256 bytes RAM min.)
Game logic
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Large state machine
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Can be slow (but preferably not)
Computational Constraints (cont.)
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Board sensor data
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Scanning row/column logic
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Time response to a voltage change
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Calibration – simple arithmetic with parameters
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Upper bound 1 second to scan entire board
External I/O
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USB connection
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Published libraries use 2 dedicated pins
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Must have USB module on-board
UART to USB chip (e.g. FT232R)
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3.3V – 5.0V I/O
Internally clocked
Internal I/O : User Input
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Rotary Pulse Generator
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2 digital inputs
Challenge buttons
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4 digital inputs
Internal I/O : Displays
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4 LCD Screens (probably TG12864H3-05A)
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At least 128x64 for required text
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3.3V max voltage @ max 1mA
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SPI interface
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Minimum 6 pins (for all 4)
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Maximum 16 pins (for all 4)
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1 KByte of RAM to fully buffer
RGB LED backlights
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Voltages of B:2.0V, R,G:3.1V @ 18mA
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Need 12 PWM channels!
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Will need an external chip
Internal I/O : Capacitive Sensors
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Measure the time constant of a circuit
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Drive pin and input pin on a timer module
Logic to isolate the correct circuit
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Minimum 1 pin (clock with external logic)
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Ideally 8 pins (4 each for row and column
select)
Internal I/O : Memory
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I2C EEPROM
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At least 1MB
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e.g. CAT24M01XI-T2
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3.3V logic levels
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400KHz max
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I2C communications
Peripherals: On-Chip
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1 – USB Module OR UART
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1-2 – I2C (PWM / EEPROM)
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1-4 – SPI (Displays)
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1 – Input Capture Timer Module
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6 – Digital Inputs
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9-16 – Digital Outputs
Potential Microcontrollers
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Freescale MC9S08JE128CMB
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Minimal
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Little bloat
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Cheaper
Microchip PIC24EP256GU810
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Fulfills maximum requirements and more
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More expensive
Peripherals: Off-Chip
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External LED Driver
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e.g. MAX6965
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Open drain outputs – set correct voltages
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3.3V input logic
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I2C interface
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8 bit PWM outputs
UART to USB bridge (if not a module)
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e.g. FT232R
Level translator / Optical isolation
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Sensor package and micro
Power Constraints
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ICs are all 3.3V
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Sensors may be better with higher voltage
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Can use unregulated AC->DC wall wart
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Reduce to 3.3V for ICs
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Plenty of room in packaging, low risk of
overheating
Costs
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Competition
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Most expensive physical board - $175
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Electronic hand-held units - $30
Target MSRP of $200