Wireless Music Dock - WMD Portable Music System with Audio Effect Applications Preliminary Design Report EEL 4924 Electrical Engineering Design (Senior Design) 26 January 2011 Members: Jeffrey Post and Lester Weaver
Page 2/7 Table of Contents Project Abstract 3 Introduction 3 Features and technical objectives 4 Flowcharts 5 Materials and Costs 6 Division of Labor 7 Figure 1: Basic Function Diagram 3 Figure 2: Transmitter flowchart 5 Figure 3: Receiver flowchart 5 Figure 4: Analog input diagram 6 Figure 5: Gantt Chart 7
Page 3/7 Project Abstract: The objective of this project is to design a docking system for any music player with portable wireless speakers and a built in equalizer to play music wherever and whenever the user desires. With many devices already available on the market, this device will differ from others thanks to built in digital effects and use of lithium ion batteries to supply sufficient portable power. Two black boxes will be designed specifically: a transmitter and a receiver. Any mp3 device can be utilized as an input to the transmission end of the design making use of the analog output jack. After adequately digitizing the signal, a digital signal microprocessor with a high clock speed will perform the digital manipulation and computation to create the effects. The signal will then be transmitted digitally and wirelessly at a high bit rate to the secondary receiving station. Once received, a micro-controller or DAC will output the signal through an amplifier to suppress any supplementary noise from transmission. The receiving station will be powered by a rechargeable battery that will need to be occasionally charged through an AC outlet or with the base transmission station. Introduction: This music dock serves as a home entertainment system for general recreational purposes. With the popularity of music in modern society this system can provide an easy and accessible solution getting rid of wires while maintaining performance. The hands on equalizer can add additional entertainment for experimenting with effects. This project uses an analog input and output with digital signal processing as well as implementing lithium ion batteries as a power source. One solution to sending the audio signal wirelessly is to utilize a Bluetooth device. Bluetooth incorporates an integrated transceiver that already modulates the signal in order to identify it from other ambient noises. Data can also be transferred easily over short distances in the microwave radio frequency range over 2.4GHz. Figure 1: Basic Function Diagram
Page 4/7 Features and technical objectives: The main objective of this project is to complete a docking station which will transfer an audio signal from an mp3 device wirelessly to a receiving station on a speaker. It will be possible to digitally manipulate the audio signal in order to set desired equalizer settings or create effects. Analog Components: An Input Differential Amplifier to control the left and right stereo channel voltages. The 3.5mm TRS connector will transfer analog information from the audio device to the base station. A Power Amplifier to control the amplitude or volume of the audio signal. Lithium Ion batteries to make the receiving stations completely wireless. Potentiometers/knobs will provide easy user input of desired effects. Digital Components: An analog to digital converter and a digital to analog IC with high resolutions to maximize audio quality will provide an easy method to switch between the analog input/output amid the digital processing. A digital signal processor, specifically the TMS320F28335 micro-controller developed by Texas Instruments will perform all the necessary audio processing. This processor features many general I/O pins, a fast 150MHz clock speed, sufficient internal memory, and has relatively low power consumption to meet all the requirements of this design. A keypad will be interfaced and will provide an easy way for the user to input the desired equalizer settings or choose among the audio effects. A LCD screen will also be interfaced to provide the user feedback for the chosen equalizer settings and selected audio effects. The wireless connectivity will be controlled by a transceiver IC or utilize the already available Bluetooth technology. Depending on the wireless transmitter utilized the signal may need to be encoded or modulated before transfer to help identify the signal from other ambient noises. A RF transmitter has the advantage of not requiring line of sight and can send data over greater frequencies. One area of concern is that the audio signal requires a high data transfer rate. Data will be transmitted digitally and must be completely received.
Page 5/7 Figure 2: Transmitter flowchart Figure 3: Receiver flowchart
Page 6/7 Figure 4: Analog input diagram Materials and Costs: Component Cost estimate DSP (TMS320F28335) $20 Bluetooth $50-$70 (depending on range of device) LCD screen <$30 Op Amps $25.00 Misc. $10.00 (resistors, capacitors,3.5mmtrs connector) PCBs: $50 One base station, two receiving stations DAC & ADC $10 Lithium Ion Batteries and Charger $10 - $50 Speakers $20 Total Cost Range $215-$275
Page 7/7 Division of Labor: Jeffrey Post will be responsible for the following aspects including: Digital effects software coding Interface of LCD and coding Wireless Connectivity Issues Lester Weaver is responsible for the following aspects including: Input and Output Amplifier analog design A/D and D/A implementation Lithium Ion battery supply power PCB layout for both receivers and single transmit stations While these responsibilities have been designated on paper both members have background knowledge for every aspect of this design excluding the wireless and lithium ion problems and will thus work together to accomplish and exceed all set goals. Gantt Chart: Figure 5:Gantt chart