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Remote System Restarter. ECE 4542-01: Senior Design II Mississippi State University October 4, 2005. Presentation Overview. Background Information Current Status Design Requirements Hardware Aspects Software Aspects PCB Layout Where we are headed. Remote Control System Access .

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Remote system restarter l.jpg

Remote System Restarter

ECE 4542-01: Senior Design II

Mississippi State University

October 4, 2005

Presentation overview l.jpg
Presentation Overview

  • Background Information

  • Current Status

  • Design Requirements

  • Hardware Aspects

  • Software Aspects

  • PCB Layout

  • Where we are headed

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Remote Control System Access

  • Access computer from anywhere

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  • File Access

    • Homework

    • Personal Files

  • Server Update

    • Web Updates

    • Maintenance

  • Technical Support

    • Computer Assistance

    • Helping a Friend

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Team Assignments

Thomas Brown

PIC software

Audio Playback

PC interface

Lindsey Coggin

Team Leader

PIC software

Audio Playback

DTMF decoding

Ken Bush

PCB Layout


Bret Birdwell

Ring Detection

PC interface

Hook control

Dr. Follett


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  • The prototype works!!!!

  • Needs some fine tuning….

    • Add more messages for the user

    • Make DTMF decoder more sensitive to tones

    • LM386 is too noisy and so is the LM471 op amp

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Senior Design II Goals

  • PCI slot

  • Detect button presses 95%

  • Understandable audio

  • Will go to a “locked” state

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  • Password Protection

  • Consecutive Failure

    • Device Disables

    • Must be Manually Reset

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Hardware Flowchart












Audio Playback

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Ring Detection

Microcontroller will need to have ability to count number of rings

  • Convert 90V AC ring signal to 5V DC pulses

  • Use input pin on microcontroller for counting pulses

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Ring Detection

  • Build or use IC with ring detection?

  • Decision: Build it!!

    • ICs would have wasted functionality

    • Cost

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DTMF Decoder

  • Dual Tone Multifrequency (DTMF) Decoder used to decode button presses of touch-tone keypad

  • Allows RSR to receive commands from user

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DTMF Decoder

  • Used CM8870 DTMF Decoder IC

    • Four output pins connected as inputs to microcontroller

    • Output is 4-bit binary number

    • Cheap

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Audio Playback

  • Audio playback needed to play recorded messages to user as instructions

  • Options:

    • EEPROM with DAC

    • Audio Record/Playback IC

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  • Serial EEPROMs:

    • Overclocking I2C SCL line

    • Not enough address pins

  • Parallel EEPROMs:

    • Expensive

    • Would use too many I/O pins on microcontroller

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  • Audio Record/Playback IC

    • Analog inputs and outputs

    • Can store analog or digital data

    • Can store 8 minutes of audio

    • Controlled via I2C bus

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  • Minimum Requirements:

    • Coil voltage of 5V

    • High coil resistance

    • Current rating of at least 20mA

    • FCC Part 68 compliant

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Test Plan

  • Each part tested independently before added to the rest of the circuit

  • Ring Detection

    • Connected to telephone network and called

    • Check output with oscilloscope

  • Voltage Regulators

    • Use oscilloscope to check voltage supplied to circuit

  • DTMF Decoder

    • Diodes used at output pins to visually see decoded key press

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Voltage supply from PC

  • The voltage supplied from the stand by 5VDC pin of the computer power supply is 5.04V

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Ring Detection Circuit Output

  • Output of Ring detection circuit is low while ringing for 2.3 sec and high in between rings for 3.7 sec.

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  • Three layers

    • Top layer: PIC software (FSM)

      • Finite State Machine controls everything

    • Middle layer: ISD functions

      • Invoked by FSM to control audio chip

    • Bottom layer: I2C functions

      • Invoked to provide communication between PIC and audio chip

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Top layer: PIC software (FSM)

  • The FSM uses the bottom two layers.

  • FSM implemented using a C switch statement like below:

    #define firstState = 0;

    #define secondState =1;

    unsigned char state:

    state= firstState;


    case firstState:

    // do some operations


    case secondState:

    // do some operations



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Top layer: PIC software (FSM)

  • The FSM makes control of the program very easy.

  • Our device has 14 states:

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Middle layer: ISD functions

  • ISD functions enable audio playback of messages

  • ISD functions use the bottom layer I2C functions

  • Playback function:

    • isd_play_address(unsigned int address);

  • Stop playback function:

    • isd_stop( );

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Bottom layer: I2C functions

  • Popular communication protocol

  • Used on the master chip (PIC18) to communicate with:

    • ISD5116 Audio Chip

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Testing Software

  • Thorough testing of the FSM is important.

  • Hyperterminal is the tool used to do this using printf statements.

    • monitor current state

    • monitor what buttons are being pressed

    • monitor interrupt timer

    • monitor variable values

  • A simple example:

    • printf(“current state = onHook”);pcrlf;

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Time Line

Aug. 18

Sept. 18

Nov. 28

Oct. 18

Nov. 18


100 %

Initial PCB Layout Finished and In Hand


PCB Population

Populated Testing

DTMF Troubleshooting


Audio Troubleshooting


PIC Software Testing/Fine Tuning

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Actual Size Used

  • 6.6” X 3.5” - Cut off .7” to avoid the PCI slot, we are using wiring harness instead, much easier to use, and no drivers needed.

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PCB Layout

  • Using ORCAD to lay out board.

  • Schematic completed, board lay out 75% complete.

  • Tentative completion date 7 October

  • 5 day lead time from ordering, approx. 5 day shipping time.

  • 10 day total time to receive.

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Attachment to PC

  • Using PCI slot face plate

  • Attaching board via L-Brackets.

  • Face plate needs 2 slots for phone jacks, 2 holes for switches, and 2 holes for board mounting.

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Senior Design II Goals

  • Clear up audio messages as much as possible

  • Increase DTMF decoder reliability

  • Make as user friendly as possible

  • Make a PCB version

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  • Dr. Randy Follett

  • Dr. Robert Reese

  • Dr. James Harden