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Final Design Report EEL 4924 Electrical Engineering Design
Wireless Speakers
Team Members:
Lawrence Pham [email protected]
Baotung Tran [email protected]
Project Abstract
Our project is to design and construct a 2.4 GHz wireless system, to transmit stereo audio from a
3.5 mm jack to play on a pair of speakers. The transmitter will convert the audio from analog to digital
with an Analog-‐to-‐Digital Converter (ADC) and transmit this digital data via a 2.4GHz transmitter. The
receiver will receive the digital data with minimal loss, and reconstruct the analog signal with a Digital-‐
to-‐Analog Converter (DAC). The receiver will pass this audio signal through an audio equalizer to control
the frequency response of the low, mid and high bands. A power amplifier will then be used to amplify
the audio signal and play it though passive speakers. The project will also include an audio visualizer
synchronized with the audio signal. The audio visualizer will be controlled via bandpass filters in series
with peak detectors for each band of the audio visualizer. The receiver system will be stationary while
the transmitter will be aimed for portability.
Table of Contents
Project Abstract ............................................................................................................................................ 1
Project Features/Objective .......................................................................................................................... 3
System Overview .......................................................................................................................................... 4
Schematics ................................................................................................................................................. 10
Project Responsibilities .............................................................................................................................. 15
Projected Timeline ..................................................................................................................................... 15
Conclusion .................................................................................................................................................. 16
Future Work ............................................................................................................................................... 16
List of Tables and Figures
Figure 1 -‐ Transmitter Design ....................................................................................................................... 4
Figure 2 -‐ Overall receiver design ................................................................................................................. 5
Figure 3 -‐ Visualizer Design .......................................................................................................................... 8
Figure 4 -‐ Voltage Regulator Schematic ..................................................................................................... 10
Figure 5 -‐ Wireless Schematic .................................................................................................................... 10
Figure 6 -‐ Audio Codec ............................................................................................................................... 11
Figure 7 -‐ Equalizer Schematic ................................................................................................................... 12
Figure 8 -‐ Power Amplifier ......................................................................................................................... 13
Figure 9 -‐ Audio Visualizer .......................................................................................................................... 14
Figure 10 -‐ Project Responsibilities ............................................................................................................ 15
Figure 11 -‐ Gnatt Chart ............................................................................................................................... 15
Project Features/Objective
The purpose of this project is to allow the wireless transmission of stereo audio from a 3.5mm
source, (ie. mp3 player, phone, computer, etc) to a pair of passive speakers. This project will also include
an audio equalizer to boost/cut low, mid, and high bands of the audio to match the frequency response
of the speakers, and the user’s personal tastes at the receiver. The receiver end of the wireless speakers
will also include an audio visualizer rendered in real time and synchronized with the audio played
through the speakers.
The main objectives for this project are:
- Effectively transmit and receive high quality audio (128 kbps) from a 3.5mm jack and play
through speakers wirelessly
- Low power transmitter so that it can be powered with 9V battery and be small and portable
- Design an audio equalizer that can weaken and strengthen low, mid and high frequency bands
by at least +/-‐10 dB, by passing the audio signal through 3 parallel active filters and then a
summer to restore the audio signal.
- Produce enough power to speakers to have “loud” music while limiting noise and distortion
- Design an audio visualizer that will be controlled by the MSP430 using analog band pass filters
and peak detectors.
System Overview
The system will first convert the analog music to digital using a stereo audio codec (TLV320AIC3204). This data will be transmitted wirelessly to the receiver. The receiver will then convert the digital data back to an analog signal. The low, mid and high frequencies will be adjusted by a 3 band equalizer and passed in parallel to the power amplifier and visualizer, so that adjustments in the audio can be heard and seen simultaneously.
Transmitter ModuleCC8520
ADC (Stereo)TLV320AIC3101
Low Noise Voltage Regulator
Range ExtenderCC2590
Device with 3.5 mm jack
Transmitter
FIGURE 1 -‐ TRANSMITTER DESIGN
Bass, Mid, Treble Control
Receiver ModuleCC8520
DAC (Stereo)TLV320AIC3204
Low Noise Voltage Regulator
Range ExtenderCC2590
Receiver
Power Amplifier
Audio Equalizer
MSP430
Audio Visualizer
Speakers
FIGURE 2 -‐ OVERALL RECEIVER DESIGN
Wireless Link:
The wireless link between the transmitter and receiver will use Texas Instrument’s
PurePath Wireless Audio Solution. The transmitter and receiver will use TI’s CC8520
System-‐on-‐a-‐Chip (SoC) to stream stereo audio to speakers. Other possible solutions to
wireless stream audio are Nordic Semiconductor’s nRF24Z1 or Xbee RF modules. The TI
solution was chosen based on its higher range and faster streaming capabilities.
Pros:
• Faster streaming rate
• Has an longer range with increased transmit power and sensitivity from FEM
• Made for streaming audio – frequency hopping, bit error correction, coexistence with other 2.4
GHz standards
• Can operate autonomously – lower cost and less real estate on board design
The CC8520 can communicate through SPI or I2C to the stereo audio codec, ADC/DAC, (TLV320AIC3204)
and generate the clocks for the I2S protocol to stream the audio.
ADC/DAC
The TLV320AIC3204 is used to convert the audio into digital and back again. The audio codec also has a
built in headphone amplifier, so we can use this to create an extra pair of wireless headsets.
The audio codec uses the I2S protocol to transfer the music signal. The left channel is sent on the low of
the WCLK and the right channel is sent on the high of the WCLK.
The TL1936A-‐33 is used as the voltage regulator for both the transmitter and receiver. The low noise
and ability to use a high input voltage (+20V) is needed, because the power amplifier requires a large
voltage.
Audio Amplifier:
The audio amplifier is constructed using a chip amplifier. The chip amplifier produces the best sound per
area. The goals of the amplifier are to provide sufficient power to 8 ohm speakers.
• TDA 1517
o Pros: Simplicity (few external components), single rail low power
requirement, small heat sink requirement, reasonably low THD
o Cons: Little flexibility, low power output (6W), high THD at max output
The layout of the audio amplifier required special attention to the signal paths and the grounding, noise
can be easily introduced.
Audio Equalizer
The audio equalizer is made with active bandpass filters and a summer to
boost/cut the low, mid, and high frequencies. There is an input buffer to
increase the stability and the boost/cut is adjusted with a potentiometer
(knob). The rotational potentiometer is chosen because it will give a more
intuitive feel for adjusting the frequencies and seeing them on the
visualizer versus a digital one with buttons. A sliding potentiometer was
also considered, but it is redundant with the visualizer.
Audio Visualizer
The audio visualizer design will not consist of a LCD but a 7 column LED panel. We plan on using the
MSGEQ7 IC, which detects peaks of 7 different frequency bands and outputs a DC representation of the
amplitude to a multiplexer that is strobed. We used the MSP430 to send the strobe and reset signals to
the MSGEQ7. We then used the MSP430 to trigger darlington pairs to turn on different LED drivers at
different times to display each band. Below is a overview of the design.
FIGURE 3 -‐ VISUALIZER DESIGN
The main gripe that we had about the visualizer design was how we were turning on the LEDS.
I would of liked to use the darlington pair array to turn on certain LED segments each clock, but the
LED drivers were diretly connected to the anodes of the LEDs, which made it impossible to turn on the
LED segments individually. Therefore, we had to turn on the LED drivers individually, which added an
extra 6 ICs to the schematics. This design was very inefficient and drew a lot more current. There was
also additional leakage current which made the LED segments flicker quite a bit. Overall though, the
performance of the visualizer worked out well, and displayed all the frequencies correctly.
MSGEQ7:
Schematics
FIGURE 4 -‐ VOLTAGE REGULATOR SCHEMATIC
FIGURE 5 -‐ WIRELESS SCHEMATIC
GND19
GND18
VCC17
VBAT16
SCL15
SDA14
GPIO1213
GPIO1312
PAEN11
EN10
XA
NTN
9
XA
NTP
8
CSN
7
SCLK
6
MO
SI5
MIS
O4
GPI
O1
3
GPI
O2
2
GPI
O3
1
RSTN 20MCLK 21BCLK 22WCLK 23AD0 24AD1 25AD2 26
GND 28
GND 27
*
CC8520 Module
VCC
SCLSDA
D1LED0
10k
R1Res1
VCC
1K
R3
Res3
VCC
DINDOUTWCLKBCLKMCLK
RST
GND GND
1 23 45 67 89 10
P1
Prog
VCC
GND
RSTNRSTNSCLK
MOSIMISO
MO
SIM
ISO
SCLK
CSN
CSN
FIGURE 6 -‐ AUDIO CODEC
GND
SCL
10u
C1Cap Semi
1u
C2Cap Semi
SDA
10K
scl_pupRes3
10K
sda_pupRes3
VCCVCC
1u
C4
Cap Semi
1u
C7
Cap Semi
VCC
1u
C6Cap Semi
10uF
C5Cap Semi
1u
C9Cap Semi
MC
LK
1
BC
LK
2
WC
LK
3
DIN
/MF
P2
4
DO
UT
/MF
P2
5
OV
IDD
6
IOV
SS
7
SC
LK
/MF
P3
8SCL/SSZ 9
SDA/MOSI 10
MISO/MFP4 11
SPI_SELECT 12
IN1_L 13
IN1_R 14
IN1_L 15
IN2_R 16
AV
ss17
RE
F18
MIC
BIA
S19
IN3_
L20
IN3_
R21
LO
L22
LO
R23
AV
dd24
HPL25 LDOIN26 HPR27 DVSS28 DVDD29 LDOSELECT30 /RESET31 GPIO/MFP532
AUDIO CODEC
tlv3204
HP
_RH
P_L
DIN
DO
UT
10u
DVDD_CCap Semi
100pF
REF_CCap Semi
.1u
CioCap Semi
10u
CAvddCap Semi
MC
LK
BC
LK
WC
LK
VCC
GND
GNDGNDGND
GND
RST
VCC
IN_L
IN_R
SGND GND
0
R or L
Res3
FIGURE 7 -‐ EQUALIZER SCHEMATIC
P9 IS NOT A HEADER SCHEM PART, ITS OWN CUSTOM MADE SCHEM PART
FIGURE 8 -‐ POWER AMPLIFIER
123456789
TDA1517
TDA 1517
22u
C1
Cap2
22u
C7
Cap2
S_GND
S_GND
EQ_OUT1
EQ_OUT2
GND
2200u
C2
Cap2
1000u
C5Cap2
1000u
C6Cap2
GND GND
100u
C3Cap2
1u
C4Cap2
GND GND
VCC
10u
C8Cap2
GND
VCC
LS?Speaker
LS?Speaker
100k
low1Volume Control
100k
low1Volume Control 2 S_GND
S?
SW-PB
FIGURE 9 -‐ AUDIO VISUALIZER
Project Responsibilities
The following breaks down project responsibilities for the team.
Lawrence Pham Baotung Tran
PCB Design 70% 30%
Audio Amplifier 80% 20%
Audio Equalizer 70% 30%
Audio Visualizer 20% 80%
Assembly and Construction 50% 50%
Testing and Debugging 50% 50%
Housing 20% 80%
FIGURE 10 -‐ PROJECT RESPONSIBILITIES
Projected Timeline
The following is a tentative schedule for the project
FIGURE 11 -‐ GNATT CHART
Cost of Project The total cost of the materials of the project is 50 dollars.
- LEDs: 5 dollars
- RF Module: 5 dollars - Housing: 10 dollars - Amplifier/OpAmps: 5 dollars - Discrete Components (R,C,etc) : 15 dollars
Conclusion
•Project completed successfully
•Not very user friendly, need to adjust volume on both amplifier and audio source accordingly
•Equalizer is spotty, need to adjust design
•Extra boards (old)+ headphone amplifier so also have wireless headphones (extra boards have a small spur problem so a little bit extra noise)
•Visualizer has some leakage current going from breadboard to pcb. Slight dim of LEDs that are not supposed to be on.
Future Work
•Use of CC853X for 2.1 or quadrophonic audio streaming
•Use CC2591 (FEM) to increase sensitivity and range
•Use of differential line audio output on TLV320AIC3204
•Use rechargeable Lithium Ion batteries
•4 layer pcb design with better layout and use of audio detect pins
•Use of different method for driving LEDs. Very inefficient the way the design is currently implemented.
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