Hand Motion Control of an Audio Player Diana Cheng and Doris Lin 6 111 Introductory Digital Systems Laboratory December 14 2005 Version 1 1 Abstract Recent technology has taken advantage of motion sensors to accomplish basic commands usually implemented through switches or remote controls The hand motion controlled audio player created in this project will carry out basic commands such as volume control track selection audio playback and record stop and pause using hand gestures The audio player will also include a visual component displaying which functions the user is carrying out via the VGA The user will wear a three axis digital accelerometer on his her hand through which hand motions will be detected Upon starting the audio player the user will be asked to calibrate his her motion for each command the motion then being written to an SRAM After calibration the audio player will be launched and once the motion is tracked the controller will map the motion to its corresponding command and the audio player responds with the correct control of an audio file stored in one of the labkit s ZBT memories The process of testing and debugging the audio player involved first testing the accelerometer and the audio player individually The two major components were then interfaced and further analyzed The end result is an audio player which responds to the user s motion whether it is turning up the volume or skipping to a new track 1 Table of Contents 1 2 3 4 Overview 1 1 Functionality 1 2 User Interface 5 5 Accelerometer 2 1 Accelerometer Specifications 2 2 Accelerometer Interfacing 2 3 RS232 FSM to Read in Data into a Bus 2 4 Implementation of the Tilting Recognition 2 4 1 Calibration State 2 4 2 Decode State 2 5 Motion Processing 2 5 1 Using Matlab to Pre Process 2 5 2 Filter Sampling Implementation in Verilog 2 5 3 Thresholding 2 5 4 Edge Detection 2 5 5 Calibration 2 5 6 Decode 7 7 8 8 8 9 9 9 10 11 11 11 11 VGA Display 3 1 VGA Video Format 3 2 VGA Timing 3 3 Calibration Display Module 3 3 1 Divider Module 3 3 2 Character String Display and the Font ROM 3 4 Audio Player Display Module 3 4 1 Button Modules 3 4 1 1 Circle Buttons 3 4 1 2 Square Button 3 4 1 3 Triangle Buttons 3 4 2 Message Module 12 13 13 15 16 16 18 18 19 19 19 Audio Playback 4 1 Audio Interface 4 1 1 AC97 Module 4 1 2 AC97 Command Module 4 2 Audio Player Module 4 2 1 Audio FSM 4 2 2 Mode FSM 4 2 3 ZBT RAM 4 2 4 Track Memory 4 2 5 Echo Memories 20 20 21 21 21 23 24 24 25 2 5 Interfacing the Accelerometer and Audio Player 5 1 Interface Module 26 6 Testing and Debugging 6 1 Accelerometer Testing and Debugging 27 6 2 VGA Testing and Debugging 28 6 3 Audio Testing and Debugging 29 7 Conclusion 8 Future Directions 30 30 3 List of Figures Figure 1 Block Diagram Figure 2 Accelerometer chip LIS3L02DQ 3axis digital output Figure 3 RS232 FSM Figure 4 Tilt Calibrate FSM Figure 5 Original MATLAB Plots Unprocessed Figure 6 Downsampled at 16 and Filtered with a 64 Window Size Figure 7 Thresholded Figure 8 Motion Calidecode FSM Figure 9 VGA Horizontal and Vertical Sync Signals Figure 10 Initial Screen Display Figure 11 Calibration Display in Countdown Figure 12 Audio Player Display Figure 13 AC97 Audio Frame Figure 14 Audio Player Finite State Machine Figure 15 Mode Finite State Machine 6 7 8 9 10 10 11 12 13 14 15 17 20 22 24 List of Tables Table 1 Command Values and Corresponding Function 4 26 1 Overview 1 1 Functionality The hand motion controlled audio player simulates a typical audio system with the usual functions like play pause stop record track selection volume control and playback mode options The unique aspect of this audio player is that it can be controlled through the user s hand gestures rather than a button press The hand gestures are detected using an accelerometer that will transmit data to the FPGA depending on what motion was done There will be an initial calibration stage in which the user is instructed to calibrate a gesture for a specific command After calibrating the user can then use the audio player by first recording audio The audio can then be played back with various manipulations including volume control and track selection In addition the different playback options of the audio player include normal playback echo mode Alvin the Chipmunk and Barry White modes 1 2 User Interface The user interacts with the audio player via a three axis digital accelerometer The accelerometer sits atop a Velcro brace that is worn around the user s hand The accelerometer is linked to the FPGA labkit with five wires These wires provide a voltage source and ground to the accelerometer along with lines to transmit and receive data to and from the FPGA Using this accelerometer the user can communicate with the audio player The audio player then communicates back by implementing the motioned audio command and also via the VGA display on a computer monitor The VGA display gives the user instructions on how to calibrate the accelerometer and then changes the display to show an audio player visualization after calibration is over The audio player display allows the user to see which functions are being carried out with simulated button pushes and messages shown on the screen A block diagram of how the accelerometer VGA and audio component interact with one another can be viewed below 5 6 Figure 1 Block diagram The block diagram shows how the accelerometer VGA and audio interact with one another and how the user can affect the audio player through its inputs iPOD and accelerometer and see and hear the results via the outputs speakers and VGA monitor 2 Accelerometer Diana Cheng 2 1 Accelerometer Specifications The accelerometer used in this project was to provide a means for interpreting and detecting hand gestures from the user This was then to be passed onto the audio portion where each gesture motion would correspond to an audio command The accelerometer used in this lab was the ST Microelectronics 3 axis 2g digital output MEMS accelerometer part number LIS3L02DQ This part came on an evaluation board EK3L02DQ which had already converted the i2c interface from the accelerometer to a standard RS232 It took an external power supply from 3 volts up to 18 and could be immediately tested and hooked up onto the Hyper Terminal There are two connections between the FPGA and the data chip a transmission line and a receiver line Figure 2 Accelerometer chip LIS3L02DQ 3axis digital output The evaluation board came with power regulations and
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