ECE 477 Final Report
Spring 2004
Team Code Name: Team mixMasters Team ID: 7
Team Members (#1 is Team Leader):
#1: Clewin McPherson Signature: ______Date: ______
#2: Jim Bauerle Signature: ______Date: ______
#3: Ruth Devlaeminck Signature: ______Date: ______
#4: Nick Schnettler Signature: ______Date: ______
ECE 477 Final Report Spring 2004
REPORT EVALUATION
Component/Criterion / Score / Multiplier / PointsAbstract
/ 0 1 2 3 4 5 6 7 8 9 10 / X 1Project Overview and Block Diagram / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Team Success Criteria/Fulfillment / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Constraint Analysis/Component Selection / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Patent Liability Analysis / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Reliability and Safety Analysis / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Ethical/Environmental Impact Analysis / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Packaging Design Considerations / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Schematic Design Considerations / 0 1 2 3 4 5 6 7 8 9 10 / X 2
PCB Layout Design Considerations / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Software Design Considerations / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Version 2 Changes / 0 1 2 3 4 5 6 7 8 9 10 / X 1
Summary and Conclusions / 0 1 2 3 4 5 6 7 8 9 10 / X 1
References / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Appendix A: Individual Contributions
/ 0 1 2 3 4 5 6 7 8 9 10 / X 4Appendix B: Packaging / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Appendix C: Schematic / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Appendix D: Top & Bottom Copper / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Appendix E: Parts List Spreadsheet / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Appendix F: Software Listing / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Appendix G: User Manual / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Appendix H: FMECA Worksheet / 0 1 2 3 4 5 6 7 8 9 10 / X 2
Technical Writing Style / 0 1 2 3 4 5 6 7 8 9 10 / X 5
CD-R of Website Image / 0 1 2 3 4 5 6 7 8 9 10 / X 2
TOTAL
TABLE OF CONTENTS
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ECE 477 Final Report Spring 2004
Abstract
An MP3 turntable. The unit will load MP3’s from a Compact Flash card and then allow the user to manipulate the loaded file as though it was a vinyl record on a turntable. An LCD display, various pushbuttons, a slide potentiometer, an RPG, and a turntable platter will comprise the user interface.
1.0 Project Overview and Block Diagram
1.1 Project Overview
The B.E.A.T.S. (Breakthrough Electronic Audio Turntable System) will manipulate the playback of an MP3 using a rotary pulse generator and a side potentiometer. MP3’s are made available to the player through the use of an interchangeable Compact Flash card on which the files may be stored. As the user rotates a turntable platter, an RPG at the base of the platter will provide interrupt data to the main processor, which will interpret the movement. The processor will, in turn, translate that movement for application to MP3 playback. Device status and user interface will be provided by an LCD display, a linear potentiometer, and various pushbuttons. As songs are played and manipulated, the LCD display will track the features being used as well as song progress. An MP3 decoder as well as a D/A converter will perform the actual playback. The pushbuttons will allow the user to select a song to load as well as initiate play, pause, stop, skip, cue, and loop. The slide potentiometer will allow the user to apply constant tempo changes. The entire system will be powered by an inexpensive 5 VDC power supply.
1.2 Block Diagram
2.0 Team Success Criteria and Fulfillment
1.) Ability to input a velocity vector using the RPG
a. This criterion was met in full.
b. Though the MP3 failure prevented us from demonstrating the application of the data gathered from the RPG, we were able to display the results of polling the device to the LCD.
2.) Ability to output standard MP3 playback
a. This criterion was not met.
b. We believe the number of errors on our PCB directly contributed to this module’s lack of completion.
3.) Ability to read data from a compact flash reader
a. This criterion was not met.
b. We believe that the number of errors on our PCB directly contributed to this module’s lack of completion. The major error related to this module was mislabeled footprint which led to a faulty layout and, in turn, a faulty PCB. The header was subsequently fly-wired, but to no avail.
4.) Ability to display information concerning MP3 playback using an LCD display
a. This criterion was met in full.
b. Though real-time MP3 playback data was not available, we were able to demonstrate the functionality of this module using hard coded values.
5.) Ability to manipulate the MP3 playback
a. This criterion was met in full.
b. Though MP3 playback was not available, we were able to demonstrate the functionality of this module using the Python prototype script on a Sun Station.
3.0 Constraint Analysis and Component Selection
The design constraints in this project are logically divisible into three classes: data transfer, user interface, and packaging. Data transfer constraints surface as a result of compact flash usage. User interface constraints are generated by ergonometric considerations, the need for sufficient tactile feedback, and the gathering of real-time data. Since the ultimate goal is to reproduce the look and feel of a vinyl turntable, packaging constraints arise because the entirety of the system must fit inside a portable case. Finally, as with most design projects, the primary constraint above all others is project cost: the project most operate within a collegiate student’s budget.
3.1 Constraint Analysis
The MP3s will be loaded into the system from a compact flash card, an interface that does not support data streaming. Furthermore, manipulation of the file in play requires that a large portion of the song be readily available to prevent gaps in playback. These restrictions introduce the first design constraint: the need for large microprocessor memory banks. The memory capacity of the chosen microprocessor must be at least 512 KB to accommodate the song buffer in addition to other dynamic allocation for function calls and local variable declarations. Given this much storage, compact flash data transfer restrictions are accommodated as are the restrictions imposed by the need for seamless playback.
The user operating the turntable will most likely be standing over the device. The line of sight from the user’s eyes to the system display will therefore be, on average, at least 3 feet. This introduces the second design constraint: the need for a system display large enough to be readable at a distance of 3 to 4 feet.
The system display is not the only portion of the user interface that generates design constraints. Though many of the features can be implemented with pushbuttons, (play, pause, stop, cue, and loop) the pitch/jog control must give the user a legitimate sense of moving a record back and forth. This necessity fosters two design constraints: the need to provide adequate tactile feedback to the user and the need to gather rotational data as a velocity vector.
The packaging design constraint goes somewhat hand-in-hand with the user interface constraint of adequate tactile feedback. Not only does the user interface need to be comparable to that of a standard vinyl turntable, but it also needs to be compact enough to be portable like all other DJ equipment.
3.2 Rationale for Component Selection
Microprocessor: As was previously stated, a design requirement for the microprocessor was that have enough memory to accommodate loading at least 30 seconds of an MP3. According to its data sheets, the Rabbit 2120 microprocessor core module comes with 512K of SRAM and can accommodate 6 additional off chip memory modules. The Ultimodule SCM220, on the other hand, offers 8MB of SRAM as well as 1MB of parallel flash 16MB of serial flash. Both processors have an adequate number of input pins for the peripherals that the project requires, but the Ultimodule SCM220 has limited support. Though it has less main memory, the Rabbit 2120 was selected due to its proven technology and widely available support.
Rotational Sensors: Original proposals for this project called for the use of an array of phototransistors (Panasonic SSG PNA1401L) in conjunction with a focused LED beam to sense rotational motion. The beam would be mounted on the underside of the turntable platter while the transistors would be installed along the inner wall of the platter bay. As the platter would rotate, the beam would pass over each transistor, and then the transistor data would be in turn fed to the processor for interpretation. While this scheme made sense on paper, the reality of project timing constraints (one semester for production) and budgetary constraints (phototransistors are roughly $4 a piece, making an array of them upwards of $40, not counting how many might be damaged in prototyping) motivated a search for cheaper solutions. The resulting find was a Grayhill Rotary Pulse Generator (series 25L). Mounted at the base of the turntable platter, this inexpensive device will provide 36 discrete of data points per rotation in addition to directional indications. Selecting the RPG over the phototransistors simplified the gathering of rotational data while still allowing for easy interfacing to the tactile feedback mechanism desired.
System Display: Before considering line-of-sight/ergonometric issues, the display selected was the Crystalfontz CFAG12864B-TMI-V 128x64. The original thought was that a backlit display such as this would take care of any line-of-sight issues. The more it was discussed, however, the more it became apparent that backlighting wasn’t enough – if the font wasn’t big enough, the user would have to crouch over the display to read it. Judging that this was unacceptable, we chose the PJRC 24x8 MP3 player display. Though this model isn’t backlit (the backlit version of this model was over $100), the size of the font is considerably larger than that of the Crystalfontz model. To keep cost down, the number of characters that can be displayed is lower than that of the Crystalfontz, but it was decided that this was an acceptable tradeoff. An added benefit is that the PJRC model comes with a 12 key pushbutton board, a feature which simplifies our user interface significantly.
MP3 Decoder/Digital to Audio Converter: While these components do not contribute directly to the design constraints, they are an integral part of the design, and therefore merit mention. Initial plans called for use of the Micronas MAS 3507D MPEG Decoder in conjunction with the Micronas DAC 3550A Stereo DAC. These components were sold as a package from Micronas, and this was attractive from the standpoint that interfacing notes came with the package. It was later discovered, however, that the Micronas line of MPEG decoders was unreliable. We replaced that pairing with the ST STA013 MPEG 2.5 Decoder and the Cirrus Logic CS4334 Stereo D/A Converter. The ST MPEG Decoder is noted as interfacing well with the Cirrus D/A Converter, which was again attractive. In addition, the ST MPEG Decoder features a variable speed internal clock, a feature which should make tempo variations fairly simple to implement.
4.0 Patent Liability Analysis
One of the components of building a product for manufacture is to examine the possible patent infringements. The individual components were purchased intact and the manufactures of these components have already resolved any patent issues. We do not need to examine infringement problems for these. The areas that need to be examined are the functions that are being implemented by the digital turntable. Possible infringement problems are analyzed below. [29]
4.1 Results of Patent Search
In examining the patents accessible through www.uspto.gov, there were no patents found in which literal infringement was committed. However there are a few patents which have similar functions.
The first patent examined is patent 6,618,329: Digital audio signal player having a simulated analogue record. This patent covers a control element which is electronically connected to an audio signal processor and a microprocessor. The microprocessor can detect the difference between a glitch and an original signal. The control element has a sensor for sensing the rotating speed and direction so as to make the audio signal processor to process and send out the data according to the movement of the control element. Therefore the user can rotate the control element with the hands to decide on the playing speed and direction so as to play the music with changed tone and speed. The idea of this patent is very similar to ours, except that this patent uses a CD on a CD player instead of MP3’s on a compact flash card. It also does not need to use the LCD screen that we use for song selection.
ABSTRACT: A digital audio signal player having a simulated analogue record includes a laser pick-up used for reading the data of an analogue CD, a microprocessor, a digital audio signal processor electrically connected to the microprocessor, a digital/analog converter electrically connected to the audio signal processor, and a turnable control element. The data of the CD is stored in a RAM of the audio signal processor. The control element is made of conductive materials, and electrically connected to both the audio signal processor and the microprocessor, and can send a glitch to the microprocessor when touched by the user's hands. The microprocessor will make the audio signal process and send out the data on detecting that the difference between the glitch and an original signal exceeds a preset amount. The control element has a sensor for sensing the rotating speed and direction thereof so as to make the audio signal processor to process and send out the data according to the movement of the control element. Thus, the user can rotate the control element with the hands to decide on the items of the music and the playing speed and direction so as to play the music with changed tone and speed. The music is played in the original normal way as soon as the user removes the hands from the control element for disappearance of the glitch. [28: 6,618,329]