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TITLE PAGE
IBM PC Voice Mail Card
By
Daniel A. Durbin
Senior Project
ELECTRONIC AND ELECTRICAL ENGINEERING DEPARTMENT
California Polytechnic State University
San Luis Obispo, CA
1989
APPROVAL PAGE
Title: IBM PC Voice Mail Card
Author: Daniel Durbin
Date Submitted: March 15, 1989
Copyright (C) 1989 by Daniel Durbin
______________________ ________________________
Prof. Arthur Dickerson Signature
Senior Project Advisor
______________________ _________________________
Dr. James D. Harris Signature
i
TABLE OF CONTENTS
Section Page
ABSTRACT............................ iv
I. INTRODUCTION........................ 1
A. Purpose...................... 1
B. Problem...................... 1
C. Solution..................... 2
II. BACKGROUND.......................... 3
A. IBM PC Bus Interface......... 3
B. Telephone Line Interface..... 5
C. A/D and D/A Conversion....... 6
III. REQUIREMENTS........................ 7
IV. DESIGN.............................. 8
A. Address Decode............... 10
B. Data Bus..................... 13
C. Voice Digitizer.............. 15
D. Voice Reproduction........... 18
E. Audio Input Amplifier........ 18
F. Audio Output Amplifier....... 21
G. Telephone Interface.......... 22
H. DTMF Decoder/Ring Detector... 24
I. Software Program............. 27
V. DEVELOPMENT AND CONSTRUCTION........ 28
VI. TEST RESULTS........................ 29
A. ADC Test..................... 29
B. Audio End-around Test........ 30
C. DAC Test..................... 32
D. Telephone Interface.......... 32
E. Answering Mode Test.......... 32
F. Integrated test.............. 33
VII. CONCLUSION......................... 34
VIII. BIBLIOGRAPHY....................... 35
ii
APPENDICES
Section Page
A. Specifications....................... 35
B. Parts List and Costs................. 36
C. Wire List............................ 39
D. IC Location Diagram.................. 41
E. PC Board Layout...................... 42
F. Program Listing...................... 44
G. Hardware Configuration/Layout........ 49
TABLES
II-1 IBM PC Bus Pin-out................. 4
IV-1 Address Assignment................. 12
IV-2 Control/Status Register Bit Asgmnt. 15
V-1 Frequency Response Data............ 31
D-1 Wire List.......................... 39
FIGURES
IV-1 General Block Diagram.............. 9
IV-2 Address Decode Schematic Diagram... 11
IV-3 Data Bus Schematic Diagram......... 14
IV-4 Audio Input/Output Schematic Diagm. 19
IV-5 Telephone Interface Schematic Diagm 23
IV-6 DTMF Decoder Schematic Diagram..... 25
IV-7 Ring Detector Schematic Diagram.... 26
V-1 Frequency Response Plot............ 30
D-1 Wiring Diagram..................... 40
E-1 IC Location / PC Board Silkscreen.. 41
F-1 PC Board Layout - Component Side... 42
F-2 PC Board Layout - Solder Side...... 43
iii
ABSTRACT
The Voice Mail Card (VMC) functions as an
enhanced telephone answering machine and is
designed as a plug in card for the IBM PC and
compatibles. In addition to regular answering
machine functions, the VMC features programmable
outgoing message selection, response to caller's
touch tone signals, and remote programming
ability.
The function of the Voice Mail Card is to answer
incoming telephone calls, deliver outgoing
messages which are programmably selectable from
16 digitized audio messages which are stored on
the PC's hard disk, to record incoming messages
to the hard disk or optionally to an external
cassette tape recorder, to respond to a caller's
touch tone signals, and to enter a remote
programming mode as a result of a special code
sent by the caller.
Audio messages are processed digitally via A/D
and D/A converters which receive and send 8 bit
data to and from the IBM PC through a selectable
port address. A/D conversion is implemented
with the ADC0802 which is operated at a clock
rate of 512 Mhz.
iv
At this frequency, the conversion rate of the
ADC will be 8 khz yielding a bandwidth of 4 khz
which is the limit of the telephone line. This
same clock is used for D/A conversion which is
implemented with the DAC0830. 8 bit data is
read/written to/from the card via software and
stored on the hard disk or optionally to an
external cassette tape recorder.
Data is transferred to and from the card through
I/O port address 0278h which may be changed as
necessary by dip switch selection. A software
program controls data read and write operations.
A full featured pull-down windowing program is
provided which controls all features of the VMC
and operates in answer mode, program mode,
message record, and message playback modes.
A/D and D/A conversion, telephone line speech
interface, ring detection, and DTMF decoding are
performed by pre-packaged monolithic devices.
The entire circuitry resides on a 4-1/2" x 7"
printed circuit board which plugs into an
expansion slot in the IBM PC.
v
I. INTRODUCTION
A. Purpose
This project proposes an alternative to the