Budget

1
Low Cost Wireless Headphones
Design Team 9
Brian Feeny Documentation
Patrick Feeny Lab Coordinator
Brian Martin Presentation
Brunno Moretti Webmaster
Geoff O'Donnell Manager
Dr. Michael Shanblatt Team Facilitator
Budget
Abstract
Technical Approach
Team nine was given the task of creating wireless
headphones from their sponsor Texas Instruments.
The headphones were required to be low cost, low
power, and designed using TI microcontrollers. A
range of 30 feet was expected between the
transmitter and the receiver. The system was
expected to operate for a minimum of three hours
using small sized batteries. The team's solution
incorporates two MSP430 microcontrollers with
Chipcon RF transceivers. In order to realize the
low cost, low power solution, sound fidelity was
sacrificed compared to higher cost wireless
solutions on the market.
Team nines design will consist of two sides, a
transmitter and a receiver. The transmitter will
contain a MSP430F2254 as its primary
microcontroller and a Chipcon CC1100 transceiver.
First, the MSP430 will take in the analog audio
signal from an audio source. It will then perform
the steps from low-pass filtering to transmitting
the digitally encoded signal via the transceiver.
The receiver will contain a
MSP430F155 as its primary microcontroller and a
Chipcon CC1100 transceiver. The receiver will
handle the incoming data stream from the
transmitter via a Chipcon CC1100 transceiver. It
will take the digitally encoded audio signal and
perform decompression. The decompressed data will
be converted from digital-to-analog for output to
an op-amp for amplification. The amplified analog
signal will then be sent to a pair of headphones.
Introduction
In todays market there are several kinds of
wireless headphones ranging in price from 60 to
upwards of 300 leaving a gap for a low cost
solution in such area. Texas Instruments has a
desire to enter this market and has proposed team
nine to develop a solution. The solution will be
targeted towards customers who seek a low cost
option in the wireless headphone market. Such
price will require a tradeoff of sound fidelity
for cost.
Project Results
Team nines goal was to create a working wireless
headphone prototype. Although the team was
unable to complete a working prototype, the team
was able to develop a working compression
algorithm and minimized hardware design. The
team was able to develop an overall software
outline. This software outline shows the process
required to send an analog signal across a
wireless channel. Team nines research,
development, and testing help show a thorough
understanding of the requirements for wireless
communication. The design implemented should
give future developers a good foundation for
continuation of the product design. The primary
area for improvement is maintaining a stable
hardware setup. As two separate hardware
configurations failed in the same manner, the
teams first concern would be discovering the
cause of the failure. Team nine cannot state with
any certainty the cause of the hardware
malfunctions. Due to the nature of the problem
the team believes either the power up hardware or
the power up method is the cause of the problem.
Documented techniques should be implemented to
prevent such a hardware problem in future
projects.
CV
Design Requirements

• Low Cost
• Low Power Consumption
• Approximately 30ft Transmission Range
• Powered by AAA Batteries
• Incorporates MSP430 Microcontroller
• Incorporates Chipcon Transceivers
• Stereo Sound

Block Diagram of Team Nines Process of Wireless
Communication.
Testing Approach
End Product
CV
Description
When dealing with just small components such as
the MSP430 microcontrollers, there are special
needs that need to be accommodated. In order to
develop, test and troubleshoot this project
there are development boards that allows the team
to get past the size constraints and perform the
needed tasks. The development boards allows the
team to localize any problems easily and fast,
making the testing procedure easier. To test
this project, two development boards are
connected to two laptops running the development
software. The software allows the team to run
test procedures, that are pre loaded, to check if
there are any hardware problems. Once the
possibility of any hardware problem is
eliminated, testing then focuses on just the
software part of the
Team nines final design uses a MSP430F2254 for
the transmitter side because of cost and memory
size. Paired with the 2254 is the Chipcon CC1100
transmitter. Two AAA batteries will also be
paired with two capacitors and a resistor to
control voltage. A MSP430F155 will control the
receiving side paired with the Chipcon CC1100
receiver. A second pair of AAA batteries power
the receiver and the headphones. Once again, two
capacitors and a single receiver will be used to
control the voltage. The receiving side also
uses a first order amplifier. This is
accomplished by having an inverting op-amp set up
for each channel. The op-amps assist in
improving the quality of the recovered signal.
The software for the teams design was
implemented using a compression technique called
differential pulse code modulation (DPCM). The
DPCM technique involves sampling an analog signal
and finding the difference between a predicted
value and the actual value of the sample. Once
this difference has been established, a lookup
table is used to determine the value that will be
sent across the communication channel.
project. In order to test the software part of
this project the team used the troubleshooting
functions that the software contains, similar to
programming with any other compiler. One test
setup included using two development boards
specifically designed for the MSP430 and Chipcon
transceiver. This setup eliminated any hardware
issues so that the software could be tested.
Final Board Layout
Test Setup with Development Boards