Team Scribacious RabbleDesign Constraint Analysis

Paul RosswurmMitch Erdbruegger

Ben KobinWilliam Hess

Project Description

Adaptation of the board game SCRABBLE® Maintains the traditional physical tile interface... augmented by ..

Sensing tile location and value Automatically calculating and displaying scores Maintaining player profiles Validating words in the event of a 'challenge' Exposing game stats over an external interface

Computational Constraints

Not much, just pushing data around Store player info

– Very Small

– Can be slow

– Simple metrics Search dictionary for a word

– 1 MByte of data

– ~200-300 lookups for a binary search

– Can be slow (external EEPROM speed is fine)

Computational Constraints (cont.)

USB Communications

– USB module or UART w/ external USB logic

– Response latency is not critical

– Not hosting

– Libraries exist (48MHZ, 256 bytes RAM min.) Game logic

– Large state machine

– Can be slow (but preferably not)

Computational Constraints (cont.)

Board sensor data

– Scanning row/column logic

– Time response to a voltage change

– Calibration – simple arithmetic with parameters

– Upper bound 1 second to scan entire board

External I/O

USB connection

– Published libraries use 2 dedicated pins• Must have USB module on-board

– UART to USB chip (e.g. FT232R)• 3.3V – 5.0V I/O

• Internally clocked

Internal I/O : User Input

Rotary Pulse Generator

– 2 digital inputs Challenge buttons

– 4 digital inputs

Internal I/O : Displays

4 LCD Screens (probably TG12864H3-05A)

– At least 128x64 for required text

– 3.3V max voltage @ max 1mA

– SPI interface

– Minimum 6 pins (for all 4)

– Maximum 16 pins (for all 4)

– 1 KByte of RAM to fully buffer RGB LED backlights

– Voltages of B:2.0V, R,G:3.1V @ 18mA

– Need 12 PWM channels!

– Will need an external chip

Internal I/O : Capacitive Sensors

Measure the time constant of a circuit

– Drive pin and input pin on a timer module Logic to isolate the correct circuit

– Minimum 1 pin (clock with external logic)

– Ideally 8 pins (4 each for row and column select)

Internal I/O : Memory

I2C EEPROM

– At least 1MB

– e.g. CAT24M01XI-T2

– 3.3V logic levels

– 400KHz max

– I2C communications

Peripherals: On-Chip

1 – USB Module OR UART 1-2 – I2C (PWM / EEPROM) 1-4 – SPI (Displays) 1 – Input Capture Timer Module 6 – Digital Inputs 9-16 – Digital Outputs

Potential Microcontrollers

Freescale MC9S08JE128CMB Minimal Little bloat Cheaper

Microchip PIC24EP256GU810 Fulfills maximum requirements and more More expensive

Peripherals: Off-Chip

External LED Driver

– e.g. MAX6965

– Open drain outputs – set correct voltages

– 3.3V input logic

– I2C interface

– 8 bit PWM outputs UART to USB bridge (if not a module)

– e.g. FT232R Level translator / Optical isolation

– Sensor package and micro

Power Constraints

• ICs are all 3.3V

• Sensors may be better with higher voltage

• Can use unregulated AC->DC wall wart

• Reduce to 3.3V for ICs

• Plenty of room in packaging, low risk of overheating

Costs

• Competition

– Most expensive physical board - $175

– Electronic hand-held units - $30

• Target MSRP of $200