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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.
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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.
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.
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 (3.579545 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 3.579545 MHz crystal