S18: Spark - MP3 Music Player with Audio Spectrum

Abstract

The project aims to build an embedded system based music system using SJOne (LPC1758) board. The system will play music through a speaker interfaced with the board. A mobile application will be used to remotely control the system using Bluetooth. The app will be able to send the start and stop signal to play music as well as switch the song and modify volume. The playlist for music will be stored on an SD card mounted on the SJOne board. An audio decoder is required as a mediator between speaker and SJone board. It will read data from SD card using SPI interface, convert this data into audio data and send to the speaker. RGB Spectrum of Audio will be shown on the LED.

Objectives & Introduction

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Team Members & Responsibilities

• Sucheta Iyer
  • Interfacing the SJONE board with speakers via the audio decoder
• Sneha Sharma
  • Interfacing the SJONE board with speakers via the audio decoder
  • Android application
• Krishna Sai Anirudh Katamreddy
  • PCB design
• Ashwini Bhargava
  • Interfacing the SJONE board with RGB Display
• Doyal Patel
  • Interfacing the SJONE board with RGB Display
  • Android application

Schedule

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Week#	Date	Task	Actual
1	4/3/2018	Project Abstract	Completed
2	4/17//2018	Order Components (MP3 Decoder,16*32 LED Display)	Completed
3	4/24//2018	Initialize LED screen with different colors. Read music data from SD card through SPI.	Completed
4	5/1/2018	Initializing single LED and testing it with sample algorithm with different colors(completed) Initialize the Audio Decoder through SPI communication and read manufacturer ID - (completed) Read from Sjone board and play sample song - (completed) Read from Memory card(SJone) and play sample song - (in progress) Designed a PCB which can hold MP3 player shield and two SJOne boards. Connected circuits between MP3 player shield and one SJOne, LED matrix and second SJOne board. Communicating SJOne with android application using bluetooth.	Completed
5	5/8/2018	Get audio spectrum values and display on LED. Pass the song data received through SD card to the audio decoder Listen to sample music on headphone/speaker. Added Audio Analyzer to the PCB design. Reviewed all the circuit connections and dimensions between components pins. Ordered the PCB. Developing user interface on android application.	Completed
6	5/15/2018	Testing and Bug Fixing Soldering the PCB. Final Report	In Progress

Parts List & Cost

Sr. No.	Component	Cost
1	SJONE board	$80
2	Audio Decoder	$24.95
3	16*32 RGB Screen	$32.42
4	PCB	$80.00
4	Total	$297.37

Design & Implementation

Audio Breakout Board

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Hardware Design

Discuss your hardware design here. Show detailed schematics, and the interface here.

Audio Decoder

The Sparkfun MP3 Player Shield was used in this project. This includes the VS1053B MP3 audio decoder IC which decodes the supplied audio files. The audio decoder is capable of decoding audio data of various formats such as WAV, MP3, MIDI and AAC. Audio data in MP3 format is chosen for this project.

Input: MP3 audio file transmitted through SPI

Output: Audio to the headphone jack and header pins.

Bluetooth Module and Android App

The Bluetooth Module connects with the SJOne Board via UART and the data received is transmitted via Bluetooth to the SparkMusicPlayer Android App. Similarly, data sent via Bluetooth by the App is communicated via UART to the SJOne board. The entire flow is displayed below.

1. Bluetooth Module

HC-05 Bluetooth

The HC-05 Bluetooth module is used in this project. It is interfaced with the UART2 pins of the SJOne board as follows:

HC-05 RX pin - SJOne UART2 TX pin

HC-05 TX pin - SJOne UART2 RX pin

VCC pin - SJOne 3.3V pin

GND pin - SJOne GND Pin

2. SparkMusicPlayer Android App

Native Android app that connects with HC-05 module (and thereby to the SJOne Board) via Bluetooth.

Data Received by the App: A list of songs available on the SD Card mounted on the SJOne board.

Data Transmitted by the App: Control signals - Play, Pause, Stop, Volume Up/Down and Song Selection from the received list of songs.

The screen of the Android app is as shown below.

Frequency Decoder

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LED Matrix

To display frequency spectrum of music input adafruit’s 16 x 32 LED Matrix is used. It is interfacing with LPC1758 using multiple GPIO pins. The LED matrix is connected to LPC1758 board by connecting three select pins to select rows (A, B and C), selection of colors using (R1,B1,R2,B2,G1,G2), Clock (clk), OE (Output enable), and Latency (LAT) of the LED matrix to GPIO pins of LPC1758 board shown as bellow:

LED matrix R1 pin -> SJOne P0.29 pin

LED matrix B1 pin -> SJOne P0.30 pin

LED matrix G1 pin -> SJOne P2.7 pin

LED matrix R2 pin -> SJOne P1.19 pin

LED matrix B2 pin -> SJOne P1.20 pin

LED matrix G2 pin -> SJOne P2.6 pin

LED matrix A pin -> SJOne P1.22 pin

LED matrix B pin -> SJOne P2.5 pin

LED matrix C pin -> SJOne P1.23 pin

LED matrix Clk pin -> SJOne P1.28 pin

LED matrix OE pin -> SJOne P1.29 pin

LED matrix LAT pin -> SJOne P2.4 pin

PCB Design

PCB is being used to connect Sparkfun MP3 player shield, LED Matrix and Audio Analyzer with two SJOne boards.

Hardware Interface

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Audio Decoder

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Bluetooth and Android App

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Frequency Decoder

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LED Matrix

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PCB Design

PCB is designed to connect SparkFun MP3 Player Shield, LED Matrix, Audio Analyzer between two SJOne boards.

Software Design

Show your software design. For example, if you are designing an MP3 Player, show the tasks that you are using, and what they are doing at a high level. Do not show the details of the code. For example, do not show exact code, but you may show psuedocode and fragments of code. Keep in mind that you are showing DESIGN of your software, not the inner workings of it.

Audio Decoder

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Bluetooth and Android App

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Frequency Decoder

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LED Matrix

The software design to update LED matrix is as follow:

1. Disable output.

2. Disable latch.

3. Select the row using A,B and C pins.

4. Reset all the LED’s in selected row.

Light up colored row depending on value of frequency band and it’s value.

5. Enable output.

6. Enable latch.

Implementation

This section includes implementation, but again, not the details, just the high level. For example, you can list the steps it takes to communicate over a sensor, or the steps needed to write a page of memory onto SPI Flash. You can include sub-sections for each of your component implementation.

Audio Decoder

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Bluetooth and Android App

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Frequency Analyzer

The implementation of Frequency analyzer is as follow:

1. Init LED matrix.

2. Start task to get audio frequency data and send it to LED Matrix.

2.1. Get audio frequency data for all band at once.

2.2. For each data in ith band.

2.2.1. Apply filter and divide result by 128 to get proper data between 0 to 32.

2.2.2. Send row, color and frequency information to update matrix.

Testing & Technical Challenges

1. Understanding the speed of communication between SJOne-memory card and SJOne-MP3 decoder. It was a producer-consumer problem that we were facing which was playing the song is a distorted way. We had a hard time figuring out which communication had the timing issue.

Suggestions:

1. If someone would want to use this particular decoder, then we would recommend converting the sample Arduino code that comes as part of the software package to C code. It would give a good head-start to how the decoder operates on default parameters.

<Bug/issue name>

1. Late arrival of PCB.

Conclusion

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Project Video

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Project Source Code

• Sourceforge Source Code Link

References

Acknowledgement

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References Used

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Appendix

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