Wireless Phone Tic-Tac-Toe Josh Morelli

Project Description The purpose is to illustrate the interfacing of hardware and wireless phones using standard Dual-Tone Multi- Frequency (DTMF) signals. Because of delays associated with wireless phone transmissions, a time- insensitive project was necessary. Hence, Tic-Tac-Toe.

System Block Diagram

Operational Description Player A presses a button 1-9. Player B’s phone receives the tone and sends it to the DTMF decoder through the 2.5mm headset jack. Player A’s phone does the same thing simultaneously Decoder outputs a 4-bit representation of button pressed to the HC12

Operational Description (cont) HC12 immediately sends the same signal to a DTMF generator Generator sends identical tone back to Player A for acknowledgement (ACK) Once ACK is verified, HC12 processes the signal and illuminates the appropriate LED on the display board

Operational Description (cont) HC12 then processes a simple algorithm to determine if a winning sequence has been lit If a winner is found, the winning sequence of LED’s is flashed Play continues until a winner is found, or reset button is pressed

Algorithm Description First checks one diagonal and all horizontal possibilities, then rotates pattern 90 degrees to check other diagonal and vertical possibilities.

Algorithm Description (cont) HC12 will logically re-order board positions for pattern recognition. New order will allow rotation simply by bit- shifting one 8-bit register. Original Re-ordered Rotated

Display Board The display board will be the primary output component of the user interface. A 3x3 array of bi-color (red/green), three-leaded LED’s will be used to represent the traditional X’s and O’s.

Display Board (cont) The LED array will be controlled by two 16-bit serial shift registers (74LS673) to reduce the number of HC12 pins used. Two 10-bit high-output buffers (TI P/N SN74ABT827) will provide the driving current for the LED array. Each LED will have a voltage divider attached to each of its 2 anodes to control proper voltages and currents.

Display Board Schematic

DTMF Decoder 18-pin DIP IC (TDK P/N: TSC 75T202) No input signal filtering required 4-bit output, binary representation of 12 possible standard phone buttons Uses a common, inexpensive reference crystal ( MHz)

DTMF Generator 16-pin DIP IC (TI P/N: TCM5089) 4-bit row, 4-bit column input, combined to select output frequencies Output frequency error is ≤0.73% Also uses the MHz crystal

Cost Estimation