ABISS: A Bluetooth Intelligent Sound System

Transcription

1 ABISS: A Bluetooth Intelligent Sound System ECE4007 Senior Design Project Section L02, Team ABISS Project Advisor, Dr. Linda Milor Andrew Burks, Team Leader Andrew Heck Stephen Leotis Ben Wallingford Submitted December 8, 2009

2 Table of Contents Executive Summary... iii 1. Introduction Objective Motivation Project Description and Goals Technical Specification Design Approach and Details Design Approach Codes and Standards Constraints, Alternatives, and Tradeoffs Schedule, Tasks, and Milestones Project Demonstration Marketing and Cost Analysis Marketing Analysis Cost Analysis Summary and Conclusions References...13 Appendix A...14 Appendix B...15 Appendix C...16 Team ABISS (ECE4007L02) ii

3 Executive Summary A Bluetooth Intelligent Sound System (ABISS) integrates software and hardware components in order to stream audio wirelessly via Bluetooth for home audio systems. The audio streams from a Bluetooth Advanced Audio Distribution Profile (A2DP) capable device to an ABISS receiver that outputs analog audio through a 1/8 stereo mini-jack. The analog audio signal is played through a home audio system. Additionally, the ABISS software compares the signal strength of the nearby receivers, which allows the computer to be aware of the proximity of the ABISS receivers and stream audio to the receiver closest to the user. The Bluetooth EDR standard is used to transmit the audio signals wirelessly. Bluetooth was chosen because it is implemented in all current generation mobile devices. The ABISS software works on all computers with Bluetooth and Mac OS X because it is built on universally available APIs. Team ABISS is pursuing this product because it enables consumers to maintain their mobility while listening to their music at home. Comparable products are not capable of pairing with multiple devices or detecting which of the devices is closest to the user. The final cost of development of the hardware and software package is $48,928. The price for a set of two ABISS receivers with software will be $128 during the first year of sales. Over the five-year production run of 400,000 units, the total profit, after marketing and development costs, is projected to be $4,391,333. Currently, team ABISS has two working prototypes of the Bluetooth receiver and a functional software application. There are many possibilities for future development of the ABISS receiver. Possibly the most important change would be to redesign the ABISS software package to work on Windows, Linux, and mobile platforms. Team ABISS (ECE4007L02) iii

4 ABISS: A Bluetooth Intelligent Sound System 1. Introduction Team ABISS spent $ to develop a hardware device that uses Bluetooth to receive audio wirelessly and an accompanying software application that enables a computer running Mac OS X to automatically switch the audio output between Bluetooth receivers connected to separate audio systems. The software monitors the signal strength of the multiple Bluetooth receivers and streams audio to the receiver emitting the strongest signal. This software algorithm results in audio playing through speakers that are nearest the notebook computer running the software. 1.1 Objective ABISS streams audio wirelessly from a Bluetooth Advanced Audio Distribution Profile (A2DP) capable device to a Bluetooth receiver. The received digital audio signal is converted into an analog audio signal and played through a home audio system. The software aspect of the product compares the signal strength of the nearby Bluetooth receivers. By comparing the signal strengths, the computer is aware of the proximity of the Bluetooth receivers and determines the device closest to the user. The target customers for this product are users of mobile devices such as cell phones, MP3 players, or notebook computers and enjoy maintaining their mobility while listening to their audio in their home. 1.2 Motivation ABISS enables consumers to maintain their mobility while listening to their music at home. Similar devices, such as the Sony HWS-BTA2W, that stream audio wirelessly via Bluetooth to a single speaker system already exist [1]. ABISS is capable of this single speaker system function, but is also able to automatically steam audio to the closest receiver based on their location relative to the notebook computer when multiple receivers are in use. This awareness of the surrounding receivers and automatic switching function makes ABISS unique and new within the audio market.

5 2. Project Description and Goals ABISS is composed of a set of Bluetooth receivers and proximity awareness software. The Bluetooth receivers are custom designed printed circuit boards (PCBs) that contain a Bluetooth system-on-chip (SoC) and headphone amplifier circuit. The PCB is powered by a 12V AC adapter and the audio signal is output through a 1/8 TRS stereo mini-jack, as shown in Figure 1. Figure 1. Block diagram of ABISS receiver. The proximity awareness software is an application run in Mac OS X that monitors all the Bluetooth receivers signal strength and automatically decides which receiver to stream audio to based upon the highest signal strength. The overall preliminary goals of the product, which includes the Bluetooth receivers and the notebook computer running the proximity awareness software, are as follows: Allow users to have a Bluetooth audio receiver that works in the home Have the receiver work with mobile devices that support A2DP (cell phones, MP3 players) Provide software for a Bluetooth enabled notebook computer running Mac OS X that allows the user to move from room to room Priced at $128 for each set of 2 ABISS receivers, and the software will be included. Initial marketing will target tech-savvy gadget lovers All the above goals were met with the exception of the pricing projection. Development cost for one ABISS receiver was $ The cost of the prototype receiver is based on small quantity purchases of hardware components. Upon purchase of hardware components en mass, the prices are significantly decreased. With these pricing levels the projected pricing goals will be met.

6 The preliminary hardware and software specifications are shown below: Hardware Specifications: Receive Bluetooth signal from audio source Output analog audio signal through a TRS plug Software Specifications: Pair with Bluetooth audio receiver and stream audio Scan the area for available Bluetooth receivers Allow to the user to choose which receiver to use Give option to automatically switch audio receivers as notebook computer is moved All of the above preliminary specifications are implemented in the final product. The software runs in the background and the scanning function is activated by a sudden motion sensor built into the notebook computer. Automatic switching is the default capability of the software, while manual mode allows the user to choose a receiver using the built-in Bluetooth menu in Mac OS X. 3. Technical Specifications ABISS operates wirelessly within 33 feet of the receiver, and it automatically pairs with all receivers in range and streams audio to the one that is closest. The receiver sends analog audio through a 1/8 TRS stereo mini-jack and requires a 12V DC power source to operate. The Bluegiga WT32 is used as the Bluetooth module as it is Bluetooth EDR capable and also supports A2DP. The receiver supports SBC, MP3, and AAC audio compression codecs, which allows for a maximum bit rate of 723kbps. The functional specifications for ABISS receivers are displayed in Table 1 below. The functional specifications demonstrate the maximum capability of each ABISS receiver. Table 1 Functional Specifications Feature Specification Operating Range ~33 feet Number of Receivers > 1 Audio Outputs 1/8 TRS Input Voltage 12V DC Bluetooth Capabilities EDR, A2DP Supported Audio Codecs SBC, MP3, AAC Audio Bit Rate 723kbps max.

7 The final product meets all of the above preliminary specifications. The operational range, supported audio codecs, and audio bit rate are specified in the standards of Bluetooth v2.0 + EDR. 4. Design Approach and Details 4.1 Design Approach The ABISS receiver accepts a Bluetooth signal emitted from the notebook computer running Mac OS X. The Bluegiga WT32 chipset accepts the analog signal via an onboard antenna. The preprogrammed audio codec on the WT32 converts the digital audio format to analog audio. The audio signal is sent to an LM4808 headphone amplifier. The amplifier circuit eliminates most high frequency clipping and increases volume of the output signal. After amplification the analog signal is sent to the 1/8 TRS jack to be played through speakers. A 2.1mm barrel jack is mounted onto the PCB to supply power to the circuit. The 12V input is sent to two different voltage regulators. These voltage regulators output 3.3V or 5V. The smaller of the two values powers the WT32 module. The 5V voltage regulator powers the remainder of the circuit. The 5V power supply provides an ample amount of power to the LM4808 to ensure optimal amplification of the signal. Located adjacent to the WT32 is a series of DIP pins. These are used in the initial programming of the WT32. This programming sets a default volume of the WT32 and initializes an A2DP sink capability on the hardware component. The completed PCB is shown below in Figure 2.

8 Figure 2. Physical form of ABISS receiver. In order to program the WT-32 module a programmer circuit was built. This circuit interfaces with the computer via an RS232 serial port. A series of MAX232 drivers were used to function as a capacitive voltage generator to supply EIA-232 voltage levels to a single 5V power supply. The MAX232 drivers are wired to a DIP header to connect to the PCB. The physical layout of the programming circuit can be seen below in Figure 3. Figure 3. ABISS programming board. The ABISS software contains the intelligence that enables the system to stream music to the closest receiver. The software s execution is triggered by a stimulus from the laptop s built-in sudden motion sensor. By using the sudden motion sensor to detect when the laptop moving, scanning of the Team ABISS (ECE4007L02) 5

9 surrounding Bluetooth receivers is performed only when the laptop is in motion. This capability eliminates the need for constant searching for Bluetooth receivers which shortens battery life and prevents unnecessary switching of receivers. During operation, the software scans all of the ABISS receivers in range for their received signal strength indication (RSSI). Using these values, the software decides which receiver is closest, and streams music to it. The program interfaces with the Bluetooth hardware of the laptop using built-in APIs of Mac OS X. Source code is available on the project website. The software is a Mac OS X application that runs as a background process. The user interacts with the program through a dropdown menu from a status item. When the software is searching for nearby ABISS receivers, which is triggered by the sudden motion sensor built into the laptop, the status menu icon spins. The dropdown menu provides a list of ABISS receivers in range, the signal strength of each, and which receiver is currently being used. The dropdown menu also gives the user the ability to choose a manual mode and select the receiver that they wish to pair to by clicking an item in the list. The application is multithreaded so that the different tasks are executed in parallel, which minimizes the impact on system performance. 4.2 Codes and Standards The Bluetooth EDR standard is used to transmit the audio signals wirelessly. Bluetooth was chosen because it is implemented in all current generation mobile devices. Bluetooth has an operating range of 33 feet and is designed for use in a personal area network, making it an ideal candidate for single-room operation. Bluetooth EDR provides a higher data transfer rate by using a combination of Gaussian Frequency Shift Keying and Phase Shift Keying modulation. The theoretical maximum bandwidth for Bluetooth EDR is 3Mbps, but the bandwidth for an A2DP transfer is limited to 723kpbs. A2DP provides enough bandwidth to transfer the highest quality MP3s, which have a bit-rate of 320kbps.

10 4.3 Constraints, Alternatives, and Tradeoffs For the Bluetooth device, the signal transmission method from the device to the home audio receiver has many possibilities. The two available output methods are RCA and TRS jacks, which were considered because of compatibility with home audio receivers. The TRS jack was chosen over the RCA jack because it is the standard for mobile devices. The TRS jack is more cost effective and uses one lead, unlike the RCA jack, which uses two leads. Bluetooth was chosen over other wireless technologies, such as and Zigbee, because Bluetooth automatically pairs with multiple devices when they are in range. Bluetooth is also an open standard, which means that all chips and devices that support Bluetooth have guaranteed interoperability. Lastly, Bluetooth has an operating range of 33 feet, which is the ideal amount for single-room use. Mac OS X was chosen over other operating systems, such as Microsoft Windows or Linux. Mac OS X has public APIs that allow a developer direct access to the built-in Bluetooth chipset as well as the built-in audio system. These APIs are critical for the proximity awareness feature of ABISS because they report signal strength and allow real-time switching between receivers. 5. Schedule, Tasks, and Milestones ABISS was designed, implemented, and demonstrated over the past three months. After the acceptance of the proposal, development began on both the hardware and the software components. Once the Bluetooth receiver schematic was completed and parts were acquired, the hardware and software was tested simultaneously because their functionality is dependent upon each other. The functional prototype was completed one month before the final presentation. The early completion of the prototype allowed for ample time to resolve any problems that arose with part acquisition and design. Once the breadboard prototype was finalized, the PCB was designed using Eagle software. Soon there after, multiple PCBs were ordered to build the final ABISS receivers. For detailed

11 information regarding the project timeline, the Gantt chart in Appendix A shows the preliminary task schedule, and the excel spreadsheet in Appendix B shows the actual progress that was made. 6. Project Demonstration ABISS was demonstrated in one large room in the Klaus Advanced Computing building on the Georgia Tech campus. Two Bluetooth receivers paired with a notebook computer running Mac OS X and the ABISS software. Each of the Bluetooth receivers were connected to a speaker system and placed in two opposite corners to simulate a multiple room setup. The demonstrator began playing music near Bluetooth receiver two and moved towards Bluetooth receiver one. ABISS automatically switched the audio stream to receiver one as its signal strength became greater than that of receiver two. Figure 4 illustrates the transition between receiver two and receiver one. Figure 4. Demonstration of ABISS in two rooms. Note the signal strength is weaker between the computer and Bluetooth receiver two and stronger between the computer and Bluetooth receiver one once the demonstrator moved closer to receiver one; therefore, ABISS is playing music through the speakers attached to Bluetooth receiver one.

12 7. Marketing and Cost Analysis 7.1 Marketing Analysis Bluetooth audio receivers using A2DP are widely available for home applications from manufacturers such as Sony, Yamaha, and Anycom. The Sony HWS-BTA2W, Yamaha YBA-10, and Anycom BAR-10 receive audio information from Bluetooth v2.0 or greater capable device using the A2DP profile. The Sony HWS-BTA2W offers a single stereo mini-jack output, while the Anycom BAR-10 has both a stereo mini-jack output and a standard RCA connection. The Yamaha YBA-10 requires a DIN-cable that connects to a proprietary dock input on compatible Yamaha audio/video receivers. Each of these products provides an operating range of around 33 feet and offer only a single speaker output option [1] [2] [3]. ABISS operates using Bluetooth EDR and uses A2DP to receive audio information. Each device uses a single 1/8 TRS stereo mini-jack to connect to an audio receiver or directly plug into to powered speakers. ABISS also has the ability to recognize the proximity of the all ABISS receivers in range and automatically switch the audio stream to the nearest receiver. This feature is not included in any Bluetooth receiver currently on the market. Proximity awareness provides the customer with the ability to experience in-room quality audio while moving throughout his/her home. 7.2 Cost Analysis A final prototype Bluetooth receiver and the required software for Mac OS X were developed for $48, The parts required for two Bluetooth receiver prototypes were purchased for $ and the labor costs for the development of the hardware and software elements was $24, The parts were purchased from distributors such as Digi-Key or obtained as engineering samples directly from the manufacturer. The total cost of developing two prototype boards was $ Table 3 shows the parts costs required for the development of two prototype ABISS receivers.

13 Table 3 - Prototype Parts Costs Product Description Quantity Unit Price Price Bluegiga WT32 2 $49.95 $99.90 Headphone Amplifier - LM $0.99 $1.98 PC Board 2 $33.00 $ mm Barrel Power Connector 2 $0.81 $1.62 1/8 TRS Jack 2 $1.50 $3.00 SMD 3.3V Voltage Regulator 2 $0.67 $1.34 SMD 5V Voltage Regulator 2 $0.78 $1.56 SMD Blue LED 2 $0.37 $0.74 Other SMD parts 2 $3.35 $6.70 Prototype Cost Total $ The majority of the costs for prototype development was for labor. An average salary per year for computer and electrical engineers, $61,738 and $60,125 respectively, was used for these calculations [4]. The cost per hour was calculated using based on equally distributed monthly income. The overhead cost for development was calculated as 100 percent of the development cost, $24, Table 4 shows the breakdown of labor costs. Table 4 - Prototype Labor Costs Project Component Labor Total Component Labor Costs Equipment Costs Hours Costs Lecture 168 $ $0.00 $ Meetings 104 $ $0.00 $ Software Design/Testing 200 $ $0.00 $ Hardware Design/Testing 200 $ $ $ Documentation 96 $ $ Total Development Cost $24, $ $24, Overhead Cost $24, Total Prototype Cost $48, The production run of the Bluetooth receivers will consist of 400,000 units to be sold over five years. The production run analysis uses single unit prices of $69, $75.90, $82.80, $75.90, $69 for the first five years, respectively, though the system will be sold with two ABISS receivers and software. The cost of the parts per unit will be $14.20 because they will be purchased in bulk with a volume discount. The parts costs are modeled to decrease five percent each year. A third party producer will provide the PC boards for the Bluetooth receiver at a cost of $1.94 per board. The product will be assembled, tested, and packaged in a manufacturing facility at a cost of $11.05 per unit. Marketing,

14 sales, and customer support will be provided at a cost of $90,000 per year. The total expected overhead cost, calculated as 150 percent the total production run cost of $10,420,586.62, is $15,630, With total revenue of $30,442, the expected total profit over the first five years is $4,391, The average profit per unit over the first five years is estimated to be $ The prototype costs are amortized at $0.18 per unit over all the units produced over the next five years. The detailed cost analysis is provided in Appendix C, while Table 5 shows a summary of the production run costs. Table 5 Production Run Cost Summary Production Run Components Component Costs Research and Development $50,000 Production $27,425,040 Package $200,000 Marketing, Sales, and Support $450,000 Distribution $447,800 Total Production Costs $10,420,587 Total Overhead Costs $15,630,880 Total Adjusted Costs $26,051,467 Total Revenue $30,442,800 Total Profit $4,391, Summary and Conclusions Currently, team ABISS has two working prototypes of the Bluetooth receiver and a functional software application. However, extensive software debugging must be performed to ensure the best possible product is ready for the public. Additionally, a protective encasement must be designed and fabricated prior to marketing. Testing of the hardware prototype has shown it ready for mass production. During prototyping of the ABISS receiver, every preliminary goal was met. There are many possibilities for future development of the ABISS receiver. In order to successfully market the ABISS receiver, it must have an aesthetically pleasing encasement. Another change that could be implemented is an onboard rechargeable battery. Having a rechargeable battery will increase the portability of the receiver and allow for usage in a car for an extended period of time.

15 In addition to the hardware changes proposed, there are some software advancements that could be employed. Adding a buffer to make smoother transitions when changing Bluetooth receivers would improve device switching. This buffer would fade music into the newly acquired receiver and fade out the music from the receiver that was previously being used. The next, and possibly most important, software change would be enabling the ABISS software package to work on Windows, Linux, and mobile platforms. This would allow for universal operability of the ABISS proximity awareness software, therefore increasing the size of the marketable populous.

16 9. References [1] SonyStyle USA. [Online]. Available: [Accessed Aug. 28, 2009]. [2] Crutchfield. [Online]. Available: 10.html?tp=243&tab=detailed_info. [Accessed Sep. 12, 2009]. [3] Anycom BAR-10 Bluetooth Audio Receiver. [Online]. Available: [Accessed Sep. 12, 2009]. [4] Most Lucrative College Degrees. [Online]. Available: [Accessed Sep. 12, 2009].

17 Appendix A Project Gantt Chart

18 Appendix B Detailed Project Timeline

19 Appendix C Detailed Cost Analysis Parts List and Prices

20 Development Costs

21 Production Run Costs