ECE 480 TEAM 13

1
Sennetech Improved Digital Answering Machine
System
ECE 480 TEAM 13
Sponsor Jim Senneker, Sennetech Inc.
Facilitator Nihar Mahapatra
Manager Mark Magee Web Manager Kathryn
Revitte Lab Coordinator Nuncio DeCia Document
Preparation Trevor Peterson Presentation
Coordinator Stas Todromovich
Abstract
The purpose of this project is to research and
develop a digital answering machine system with
high sound quality and the ability to shuttle
backwards and forwards during message playback.
Other unique features of our system include the
LCD touch screen user interface and the improved
sound quality.
Acknowledgements
Final Budget
We would like to give a special thanks to Jim
Senneker of Sennetech for his help and the
opportunity to design something creative and new.
LCD Graphical Touch-screen 279.00 LCD
Touch-screen Interface Board 30.00 PIC18F4550
Microcontroller 11.43 ISD 1110 Voice IC
Chipcorder 5.64 ISD 2560 Voice IC
Chipcorder 10.49 Cermetek CH1837
DAA 31.70 NE5532 Low Noise Op-Amp 1.68 MCP41100
Digital Potentiometer 1.78 AC-DC Wall
Transformer 21.95 Telephone Cables and
Connectors 14.24 Total 407.61
Introduction
Problem/Need For a digital answering machine
with improved sound quality and the ability to
shuttle back and forth within a message.
Intended user/usage The intended user is the
average person with a land phone line either at
home or an office. The intended usage is to
receive telephone messages. Assumptions/Limitatio
ns Our main limitation was the unavailability of
memory greater than 8MB available in DIP
packages. We assume that in production, the
memory size can be increased.
Technical Approach
Design Requirements
Design objectives To detect rings and answer the
phone, record messages, play back recorded
messages, shuttle messages during playback,
record and play an outgoing message, and detect
handset pickup.
Design constraints Design should use low power,
output high quality audio, and have an easy to
use graphical user interface.
The digital answering machine we have designed is
built around the PIC18F4520 microcontroller,
which controls the other components. The LCD
touch screen contains the graphical user
interface with which users can control the
answering machine. It is programmed in HTML and
uses the PICs USART protocol to send and receive
information from the PIC. The PIC also interfaces
with the chipcorder ICs to play and manipulate
messages. The other components of our design are
the class A-B push-pull audio amplifier, the
speaker, the microphone and the microphone
preamplifier.
End-Product Description
Our final product is a working answering machine
which can answer the phone, play an outgoing
message, record a message, play back a message,
and allows shuttling forward and backward during
playback.
Final Product/Project Results
Our design can perform most functions of an
answering machine answering the phone, playing
an outgoing message, and recording incoming
messages. In addition, it has the added
functionality of shuttling back and forward.
However, it can hold only four 15-second
messages. Future improvements would be increasing
memory size, adding USB functions, time/date
stamping, and marking messages.
Testing Approach
Testing was done by connecting the unit to a
phone line, calling the line, debugging the code,
and listening to the audio quality. Changes were
made to the design and code based on these tests.