Difference between revisions of "S18: Spark - MP3 Music Player with Audio Spectrum"

Revision as of 19:21, 23 May 2018

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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Parts List & Cost

Design & Implementation

Audio Breakout Board

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Hardware Design

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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. This module is capable of serial communication with the microcontroller over UART and is capable of sending and receiving information via Bluetooth from paired devices.

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.

SparkMusic Player App Screen

Frequency Decoder

The frequency decoder module uses the MSGEQ7 graphic equalizer display IC to split the music into 7 frequency bands. The 7 frequency bands are: 63Hz, 160Hz, 400Hz, 1kHz, 2.5kHz, 6.25kHz and 16kHz. The peak level of each band is detected and multiplexed to the output to provide a DC representation. The strobe and reset pins are used to select the DC peak output. Reset high resets the multiplexor. Reset low enables the strobe pin. At the leading edge of the first strobe, the first frequency band 63Hz is on the output. On each additional leading edge strobe the next frequency band(160Hz, 400Hz, 1kHz, 2.5kHz, 6.25kHz, 16kHz) is detected.

16 x 32 LED Matrix Fron and back side

LED Matrix

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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 Pin Connections

Audio Decoder

The Audio Decoder breakout board communicates with the SJOne board over SPI and is interfaced with the SPI-1 pins of the SJOne board as follows:

Clock Pin (Pin 13) - SJOne SPI-1 Clock Pin

MISO Pin (Pin 12) - SJOne SPI-1 MISO Pin

MOSI Pin (Pin 11) - SJOne SPI-1 MOSI Pin

MP3 CS: This is the Chip Select Pin for the audio decoder which is to be activated while sending control signals.

MP3 DCS: This is the Chip Select Pin for the audio decoder which is to be activated while sending audio data signals.

MP3 RST: This is the Reset pin for the audio decoder.

MP3 DREQ: This is the Data Request Pin through which the audio decoder signals that it is ready to accept another 32 bytes of audio data.

VCC pin - SJOne 3.3V pin

GND pin - SJOne GND Pin

Bluetooth Pin Connections

Bluetooth and Android App

The HC-05 Bluetooth module is used in this project. It communicates with the SJOne board over UART and 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

Audio Analyzer

Interface between LED and SJOne Board

This analyser takes input from Audio decoder for left and right side music. SJOne outputs values of RS and ST pins and reads input data from S pin which is connected to ADC pin (P0.26) of SJOne.

   Audio Analyzer S pin  -> SJOne P0.26 pin (ADC)
   Audio Analyzer RS pin   -> SJOne P1.31 pin 
   Audio Analyzer ST pin   -> SJOne P1.30 pin 
   Audio Analyzer + pin    -> SJOne VCC pin 
   Audio Analyzer - pin    -> SJOne GND pin

LED Matrix

Interface between LED and SJOne Board

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

Software Design

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Audio Decoder

The audio decoding works in two phases which is divided into two tasks - GetSong and PlaySong.

GetSong: This task reads the audio data from the SD Card mounted on the SJOne board through SPI. 512 bytes of data are read at a time and this data is pushed to a FreeRTOS Queue (SongQueue).

PlaySong: This task sleeps on the SongQueue. When data is available it is parceled into 32 byte chunks (from 512 bytes input chunk from queue) and transmitted over SPI to the audio decoder breakout board.

Frequency Analyzer State Diagram

Bluetooth and Android App

The project requires that the Android phone pair with the HC-05 Bluetooth device prior to using the SparkMusicPlayer App. Following this, communication follows these steps:

1. On launch the Android device forms a successful connection with the HC-05 Bluetooth device.

2. The App receives the list of songs available on the SD Card from the SJOne board and displays them as a list.

3. The App can now transmit control signals to the SJOne board - change song by clicking on the appropriate song on the list, pause, play, stop, fast forward and change volume. At each action an Android Toast message confirms the action taking place.

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.

Implementation

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Audio Decoder

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Bluetooth and Android App

Implementation from the Android App side is as follows:

1. Try to form a successful Bluetooth connection with the HC-05 module. On success, change the 'Connection Status' indicator to indicate this. At any point if the Bluetooth Connection fails, change the Connection Status indicator and prevent all further communication with Toast error messages while trying to continuously reconnect. This functionality runs as a separate thread on the App.

2. On successful connection, receive, parse and display the song list as a List.

3. Transmit control signals as per user's activity to the SJOne board.

Frequency Decoder

The software Implementation to Init frequency analyzer is as follow:

1. Select ADC pin 2. Select GPIO pin direction for reset pin and ST pin

   adc.adcSelectPin(adc.ADC_PIN_0_26);
   LPC_GPIO1->FIODIR  |= (1 << RS) | (1 << ST);

The software Implementation to Getting data for all bands are as frequency analyzer is as follow:

1. reset ST pin. 2. Give delay required to get data. 3. Read data from ADC pin. 4. Set ST pin.

    LPC_GPIO1->FIOPIN &= ~(1 << ST);
    delay_us(40);
    val[i] = adc.readADCVoltageByChannel(3);
    LPC_GPIO1->FIOPIN |= (1 << ST);

LED Matrix

The software Implementation to Init LED matrix is as follow:

1. Set Direction of all GPIO pin to output mode

2. Set GPIO pins to 0.

   LPC_GPIO0->FIODIR  |= (1 << r1) | (1 << b1);
   LPC_GPIO1->FIODIR  |= (1 << r2) | (1 << b2);
   LPC_GPIO1->FIODIR  |= (1 << clk) | (1 << oe);
   LPC_GPIO1->FIODIR  |= (1 << a) | (1 << c);
   LPC_GPIO2->FIODIR  |= (1 << b);
   LPC_GPIO2->FIODIR  |= (1 << g1)|(1 << g2)
   LPC_GPIO2->FIODIR  |= (1 << lat);
   LPC_GPIO1 ->FIOCLR = (1 << a);
   LPC_GPIO1 ->FIOCLR = (1 << b);
   LPC_GPIO1 ->FIOCLR = (1 << c);
   LPC_GPIO1->FIOCLR = (1 << clk);
   LPC_GPIO1->FIOCLR = (1 << oe);
   LPC_GPIO2->FIOCLR = (1 << lat);

The software Implementation 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.

   LPC_GPIO1->FIOSET = (1 << oe);
   LPC_GPIO2->FIOSET = (1 << lat);
   (select_line & 0x1) ? LPC_GPIO1 ->FIOSET = (1 << a) : LPC_GPIO1 ->FIOCLR = (1 << a);
   (select_line & (0x1<<1)) ? LPC_GPIO2 ->FIOSET = (1 << b) : LPC_GPIO2 ->FIOCLR = (1 << b);
   (select_line & (0x1<<2)) ? LPC_GPIO1 ->FIOSET = (1 << c) : LPC_GPIO1 ->FIOCLR = (1 << c);
   for (int i = 32; i > 0; i--) {
       if (i > len1) {
           LPC_GPIO0 ->FIOCLR = (1 << r1) | (1 << b1);
           LPC_GPIO2 ->FIOCLR = (1 << g1);
       }
       else {
           (color &  0x1) ? LPC_GPIO0 ->FIOSET= (1 << r1) : LPC_GPIO0 ->FIOCLR = (1 << r1);
           (color & (0x1<<1)) ? LPC_GPIO0 ->FIOSET= (1 << b1) : LPC_GPIO0 ->FIOCLR = (1 << b1);
           (color & (0x1<<2)) ? LPC_GPIO2 ->FIOSET= (1 << g1) : LPC_GPIO2 ->FIOCLR = (1 << g1);
       }
       if (i > len2) {
           LPC_GPIO1 ->FIOCLR = (1 << r2) | (1 << b2);
           LPC_GPIO2 ->FIOCLR = (1 << g2);
       }
       else {
           (color &  0x1) ? LPC_GPIO1 ->FIOSET= (1 << r2) : LPC_GPIO1 ->FIOCLR = (1 << r2);
           (color & (0x1<<1)) ? LPC_GPIO1 ->FIOSET= (1 << b2) : LPC_GPIO1 ->FIOCLR = (1 << b2);
           (color & (0x1<<2)) ? LPC_GPIO2 ->FIOSET= (1 << g2) : LPC_GPIO2 ->FIOCLR = (1 << g2);
       }
       LPC_GPIO1->FIOSET = (1 << clk);
       LPC_GPIO1->FIOCLR = (1 << clk);
   }
   LPC_GPIO1->FIOCLR = (1 << oe);
   LPC_GPIO2->FIOCLR= (1 << lat);

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.

2. Care needs to be taken to have mutual exclusion while using the SPI bus between the task that reads data from SD card and the task that transmits data to the audio decoder.

Suggestions:

1. If someone would want to use this particular decoder, then we would recommend looking through 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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