ECE511 Group11 Final Report 20131213...

MP3 Boombox

ECE 511 PROJECT GROUP 11

12/03/2013

CARLOS R ARAUJO

BRIAN D JARVIS

SHAWN WILKINSON

DIVYA CHINTHALAPURI

LEEGIA S JACOB

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Abstract For this project, the motivation was to create a product which would entertain the user. The group voted and an

MP3 player was selected. The goals were to create a player which would maximize the utilization of the MSP430

while at the same time be fun and intuitive to use. With five team members, it was important to derive five high

level features which would comprise the project such that each person had a decent amount of responsibility. In

the end, the MP3 player was a success. Featuring an LCD display, wireless remote, graphical VU meter, RGB led

light show, and MP3 playback, it is a wonder that a single MSP430 is controlling the entire device.

Contents Abstract ......................................................................................................................................................................... 1

Motivation ..................................................................................................................................................................... 2

Solution .......................................................................................................................................................................... 2

Components .................................................................................................................................................................. 2

MP3 Trigger ............................................................................................................................................................... 2

Hardware Interface ................................................................................................................................................ 3

Software Interface ................................................................................................................................................. 3

EQ Filter ..................................................................................................................................................................... 3



Liquid Crystal Display ................................................................................................................................................. 4



Infrared Remote and Infrared Receiver Breakout ..................................................................................................... 5



RGB LED Lighting Effects ............................................................................................................................................ 6



Results ........................................................................................................................................................................... 7

Lessons Learned ......................................................................................................................................................... 7

Achievements ............................................................................................................................................................ 7

Shortcomings ............................................................................................................................................................. 7

Conclusion ................................................................................................................................................................. 7

Appendix A: Team Member Tasking .............................................................................................................................. 8

Appendix B: Parts List .................................................................................................................................................... 8

Appendix C: Schematic .................................................................................................................................................. 9

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Motivation The team wanted to create a project which would be challenging and utilize every resource of the MSP430 while at

the same time being fun and entertaining to use. An MP3 player fit these requirements and was voted as the best

project for the team to pursue. However it was soon discovered that there was a dilemma. Decoding the MP3

format requires more processing power than the MSP430 can provide. However the dedicated MP3 decoder

boards available on the market go too far in the opposite direction, performing most MP3 player functionality by

itself. In order to ensure the project was challenging and sufficiently demanding for each team member, features

were added which would utilize as much of the MSP430 as possible.

Solution One of the key goals for the MP3 project was to maximize the resources available in the MSP430. To do this,

features were added which would utilize each available peripheral on the microcontroller. The MP3 player

features an LCD display, wireless remote, graphical VU meter, RGB led light show, and MP3 playback. These

components are implemented according to the block diagram below.

Figure 1 : MP3 Player High Level Block Diagram

In this diagram it is important to note that the MSP430 is the central controller of each external component. As

such, the software for each component was developed keeping in mind that it must coexist and share resources

with four other major components. Each of the major components are described in the sections that follow.

Components

MP3 Trigger The MP3 Trigger is the device that was selected to provide the MP3 decoding function for our project. The MP3

Trigger has 18 external input pads that when activated can trigger preselected tracks stored in an onboard micro

SD card. Furthermore, the board has a full duplex serial port that provides full transport control and remote

triggering for up to 255 tracks. The micro SD card used for MP3 storage can be formatted using a FAT 16 or FAT 32

file system from a Windows machine. At the heart of the MP3 Trigger board is a Cypress CY8C29466-24SXI 16bit

microcontroller which serves MP3 data to an onboard VS1063 audio codec IC.

The MP3 Trigger can recognize a number of commands that it receives through the serial port. We are using a

subset of the available commands to control the device, enumerated below:

• Play/Stop

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• Next Track

• Previous Track

• Volume Up

• Volume Down

In response to the above commands and other functions the MP3 trigger will provide limited feedback to the

controlling device, the MSP430. The feedback is in the form of a single 8 bit ASCII character.

MP3 Trigger Feedback:

• ‘x’ acknowledges a command execution

• ‘X’ indicates end of current track

• ‘E’ error code

Hardware Interface In an effort to save pins for the other components that were integrated to the MSP430, we decided to use the

UART to control the MP3 Trigger. The UART is multiplexed with some other internal modules in the MSP430 on

P1.1 (RXD) and P1.2 (TXD). The MP3 Trigger TXD was connected to the MSP430 RXD, and the MP3 Trigger RXD to

the MSP430 TXD to achieve full duplex communication.

Software Interface For the software part 4 files were created: one source and header file to support the MP3 control and another

source and header pair for the UART control. In the UART implementation there is an initialization file that sets all

the internal registers for the UART operation. The baud rate was set to 9600 with no parity check, and one bit

start and stop. Other functions were also created to receive/transmit a single character or a series of characters

until the new line characters was received.

The MP3 implementation has functions to control the MP3 player using some of the UART functions for single

character transmission and reception. There are two main functions in the MP3 implementation file,

MP3_sendCommad and MP3_readStatus. These two functions are called from the main loop after checking two

flags which dictate whether MP3 actions are needed. One flag indicates the latest command received by the

remote and the other indicates whether a character was received on the UART; the flags are checked before calling

the two main functions to save processor time.

EQ Filter A feature of the MP3 player is that it analyzes the audio signal being player and displays the signal levels in the

form of a graphical VU meter on the LCD screen. This is accomplished with an MSGEQ7 IC. This chip takes the left

and right channels as input, performs filtering and level detection in seven frequency bands, and outputs the level

of each band as a voltage level on its analog output pin. To represent seven frequency bands on one pin the

output is multiplexed, driven by two pins for reset and strobe from the MSP430.

Hardware Interface Three GPIO pins from the MSP430 are used to interface to the MSGEQ7 chip. Two are configured as port outputs:

one for the reset pin and the other for the strobe pin. The third pin is configured as an input to the ADC module of

the MSP430. Electrically, the MSGEQ7 has five additional pins which must be connected according to the diagram

below.

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Figure 2: MSGEQ7 Graphical Equalizer Circuit

The additional circuitry requirements depicted above allow the chip to perform its filtering and level detection

which ultimately lead to the signal level representations output to the MSP430.

Software Interface The software to control the MSGEQ7 is split into three sections: Timer Interrupt, ADC Interrupt, and Main Loop.

Timer

One of the timer modules is configured for use in controlling the MSGEQ7. The timer is configured to operate in

incrementing count-up mode. The timer interrupt is enabled and configured to interrupt every 72 microseconds.

Inside the timer interrupt service routine, the MSGEQ7 reset and strobe lines are managed. Additionally, the timer

ISR kicks off analog to digital conversion of the MSGEQ7 output according to datasheet timing requirements.

Analog to Digital Converter

The ADC module is configured for use reading the MSGEQ7 output values and digitizing them. The ADC is

configured to use the VCC and Ground as reference voltages. The ADC interrupt is enabled and set to only convert

values when commanded to do so (i.e. not continuous conversion mode). Inside the ADC ISR, the latest converted

value is simply saved into a global array which can be accessed by other portions of the software.

Main Loop

As part of the main loop of the MP3 player software, the graphical VU meter levels are updated according to the

values read from the MSGEQ7 chip. Once the Timer and ADC interrupts are properly running as described above,

an array of seven frequency band levels is updated regularly and much faster than the main loop executes. As a

result, each time the main loop iterates, new values are available in the frequency level array. At this point the

levels are written to the LCD display as a graphical representation of the playing audio signal levels.

Liquid Crystal Display A 16x2 LCD panel is used in this project as the central information display. The two significant roles of the LCD in

this project are given below.

1. Display the song title and artist: The LCD should display the song title and the artist information on the

top row of the screen while the song is being played

2. Display the VU Meter frequency levels: The LCD should display the VU meter on the bottom row of the

screen while the song is being played. The output from the MSGEQ7 ADC conversion is used to draw one

of eight custom characters representing different signal levels for each frequency band.

Hardware Interface The LCD is interfaced with the MSP430 chip using GPIO pins. Four pins are used for data, one for Enable and

another one for Register Select. The LCD drives 3.3 Volts. Therefore, it is compatible with the MSP430 chip.

Additionally, a potentiometer is used to adjust the contrast of the LCD. The hardware interface is given below.

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Figure 3: 16x2 LCD interface with MSP430

Software Interface LCD was configured to 4 bit data mode (in order to save some pins on the chip), 2 line display and 5x8 pixels on

each character. The software that was used to control the LCD module was broken down to different functions.

• LCD initialization: In this function LCD pins and its directions were set up, started the LCD, custom

characters for frequency bands are also stored in RAM.

• LCD Trigger: The LCD was triggered using the enable signal from the MSP 430 chip.

• LCD writes data: This function enables LCD to receive data on the display when Register Select = 1.

• LCD writes command: This function makes the LCD capable of receiving commands when Register Select =

0.

• LCD Cursor position: X, Y position of the LCD cursor is set up in this function.

• LCD set text: This function sets up the LCD to print strings on the LCD particularly used to display song title

and the artist information.

• LCD band setup: 5x8 pixels character mode is used to display frequency bands using levels. On a 5x8 pixels

character there are 5 columns and 8 rows in which each row is used as a level for the frequency band

display. For different frequency values, different levels are displayed. It can store up to 8 custom

characters. This function is used to draw these frequency levels on the LCD.

Infrared Remote and Infrared Receiver Breakout A feature of this project is to remotely control the MP3 functions. The functions supported from the remote are:

"Play/Stop”, “Next Track”, “Previous Track”, “Volume up/down". To implement this feature Sparkfun's Infrared

remote controller and infrared receiver breakout TSOP853 are used. The receiver breakout board consists of a

lens, preamplifier and filter units mounted on it. The codes from the remote button press are received by the

receiver at a detectable distance and are interfaced to MSP430 which in turn interfaces with MP3 functions to

trigger a particular function to be operated.

Hardware Interface The IR remote communicates with the IR receiver using infrared radiation. The remote’s infrared output signal is

modulated at 38 kHz and therefore is compatible with the IR receiver module operating at this frequency. There

are nine buttons on this particular IR remote which emits unique 32-bit codes for each button press. These codes

are received one at a time by the receiver board and are sent out on its OUT pin (Figure 5). Therefore in this

project implementation, the IR receiver's OUT pin is interfaced to MSP430 on pin P2.4 and this pin is configured as

an input pin. The remaining two pins of the receiver are Vcc and Gnd.

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Figure 4: TSOP853 Infrared received breakout board circuit

Software Interface The IR software makes use of the timer of the MSP430. As button codes are decoded the latest commands are

made available to the rest of the software so they may take action accordingly.

Timer

The IR receiver makes use of timer A1.2 on the MSP430 and is configured to operate in capture mode, capture on

both edges and with capture interrupt enabled. Upon interrupt, which is when the receiver has received a 32 bit

code and sent it in digital form on the OUT pin to the MSP430's P2.4pin, then the control is transferred to the

timer ISR. The timer ISR has the pulse definitions of the NEC protocol in terms of “mark” and “space” for the

header and data portions of the button codes (Figure 6). Depending on the width of the received pulse, either a 1

or 0 is decoded. Once 32 bits are decoded, the received code is matched against the set of expected HEX values. In

the MP3 trigger software, these HEX values are used to take action depending on which particular button was

pressed.

Figure 5: Example pulse sequence of NEC protocol

RGB LED Lighting Effects The RGB LED portion of the project including 8 RGB LEDs in the shape of a circle. The circuit was able to display

different patterns based on user input via the IR remote control. Using cascaded shift registers, the circuit is able

to individually set 24 different LEDs (8 red, 8 green, and 8 blue) using only three pins from the MSP430 (data, clock,

and latch pins).

Hardware Interface Three digital I/O pins are all that was required to send data to the three cascaded shift registers used to drive the

24 individual LEDs. One pin was used to send serial data (P2.7), one pin served as a clock (P1.6), and the final pin

served as a latch to enable/disable the shift registers (P1.7). The shift registers, which can hold 8 values each,

overflow from one to the others such that with three cascaded, 24 individual LEDs could be manipulated.

Software Interface The main “while()” loop of the program is focused on servicing the RGB LEDs. While some of the hardware used

interrupts and timers, it was up to this main loop to update the MP3 Trigger with any commands received from the

IR remote as well as updating the LCD with information from the graphic equalizer IC. After analyzing the length of

time it takes to update the MP3 Trigger and the LCD, the RGB LED changes and delays were set so that the light

patterns were consistent whether the microcontroller needed to service other components or not.

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Results

Lessons Learned One of the most important things learned was the ability to timeshare a microprocessor’s limited resources. With

four interrupts firing regularly, some of which required significant time to process, there was not always much CPU

time remaining for the code operating in the main loop. In the course of integration, the team had to react quickly

to challenges resulting from these timing constraints as they popped up.

Achievements The team was successful, first and foremost, in achieving the goal of maximizing the resource utilization of the

MSP430. Our software approached the limit of available memory on the device. So close, in fact, that we could

not create one more variable without running out of memory. When these challenges were faced, we succeeded

in working around them with clever programming alternatives. Additionally, the team succeeded in creating a fun

to use and entertaining MP3 player. Lastly, the integration platform built for the prototype was integrated and

assembled very professionally, contributing to the overall fit and finish of the MP3 player.

Shortcomings One of the team’s original goals was to design a PCB layout to be fabricated in time for the final demonstration.

Unfortunately due to scheduling and issues encountered during final integration, there was not time to send the

layout for fabrication.

Conclusion The MP3 player project set out to achieve a few specific goals. We wanted to maximize the resources available in

the MSP430 while at the same time creating a fully functional, fun, and entertaining MP3 player. Each of these

goals was met as we fully utilized the MSP430 down to the last instruction possible. Additionally the playback

functionality and remote control ability create a very fun and entertaining musical experience complete with visual

feedback in the form of lighting effects and graphical VU meter. In the process, the team gained valuable

experience integrating electronics with a low-resource microcontroller and managing the software accordingly.

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Appendix A: Team Member Tasking Each member should add their contributions into the sections below:

Carlos Araujo

Carlos was primarily responsible for the MP3 decoder, and building the integration platform. Also, He did the MP3

software integration with the LCD and IR code. He also assisted in the custom character creation for the VU meter.

Brian Jarvis

Brian was primarily responsible for the EQ Filter and graphical VU meter. He also assisted with the decoding of the

infrared remote signal and helped integrate the various software components.

Shawn Wilkinson

Shawn was primarily responsible for the RGB LED portion of the project, which encompassed both the hardware

and software portions. He ensured the RGB LED code, the graphic equalizer code, the MP3 Trigger code and the IR

remote code were all synchronized.

Divya Chinthalapuri

Divya was responsible for IR remote and IR receiver coding, and she could accomplish the task with the help of

Brian. Alongside she also assisted in preparing the final presentation slides.

Leegia Jacob

Leegia was primarily responsible for LCD module of the project that includes both hardware and software. She also

helped with the final testing of the circuit.

Appendix B: Parts List

Table 1: Bill of Materials

Part# Description QTY Vendor

MSGEQ7 Graphic Equalizer 1 Sparkfun

COM-00105 RGB LED Commond Cathode 8 Sparkfun

NHD-0216HZ-FSW-FBW-33V3C-ND 2x16 CHAR LCD 3.3VDC 1 Digikey

MSP430G2553IN20 IC MCU 16BIT 16KB FLASH 20PDIP 1 Digikey

RHM100PDKR-ND RES 100 OHM 1/4W 5% 24 Digikey

2N7000TA MOSFET N-CH 60V 200MA TO-92 1 Digikey

TC54VN3002EZB IC VOLT DET N-CH OD 3.0V TO92-3 1 Digikey

WIG-11029 MP3 Trigger 1 sparkfun

VS-MBRA140TRPBF DIODE SCHOTTKY 40V 1A DO214AC 1 Digikey

3362P-1-103LF TRIMMER 10K OHM 0.5W PC PIN 1 digikey

EEA-GA1H100H CAP ALUM 10UF 50V 20% RADIAL 2 Digikey

LD1086V33 IC REG LDO 3.3V 1.5A TO220AB 1 digikey

CC1206JRNPO9BN330 CAP CER 33PF 50V 5% 1 Digikey

CC1206KRX7R9BB104 CAP CER 0.1UF 50V 10% 3 Digikey

CC0402KRX7R7BB103 CAP CER 10000PF 16V 10% 1 Digikey

SEN-08554 IR Receiver Breakout 1 Sparkfun

COM-11759 Infrared Remote Control 1 Sparkfun

KTR18EZPF2202 RES 22K OHM 1/4W 1% 3 Digikey

SN74HC595DWR IC 8BIT SHIFT REG 3ST-OUT 3 Digikey

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Appendix C: Schematic

Figure 6: MP3 Player Schematic, Page 1

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Figure 7: MP3 Player Schematic, Page 2

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