GFX-One Guitar Processor

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GFX-One Guitar Processor

• Team Carpal Tunnel
• September 8, 2005

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Team Members

• Mason Stone
• Henock Negassa
• Tony Sawyer
• Nael Cassier

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What is GFX-One?

• GFX-One is a digital audio effects processor.
• It is designed specifically for use with guitar,
  but can process any monaural analog audio input.

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Functional Block Diagram
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Digital Signal Processor
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Why use a DSP?

• Digital data is easier to manipulate
• Implementing effects can be done using algorithms
  and subroutines as opposed to sophisticated
  analog hardware
• DSP can be altered and maintained using software

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Implementing Audio Effects

• Flanger effect is present in a lot of
  guitar-driven music
• It is accomplished by adding a signal to a
  time-varying, phase-modulated version of itself

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Fixed Delay and Reverberation

• Reverberation and echo are very common in audio
  engineering
• Both can be synthesized in DSP using comb filters
  and re-circulating delay lines

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Other Effects and Features

• Parametric Equalization
• Gain manipulation
• Auto-Wah
• Phaser
• Noise-gating
• Decimation (Aliasing)
• Many other possibilities

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DSP Interface

• What We Need
• 25 MHz Oscillator
• Flash Microcontroller
• 256 MB SDRAM
• FPGA
• I/O

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25 MHz Oscillator

• Used to synchronize digital circuitry.
• With use of PLL, provides clock speed.
• Will be connected to FPGA, then distributed.

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Flash Microcontroller

• Contains instructions for DSP.
• Internal µcontroller programs chip automatically
  over HDD interface.
• Internal code can contain image for FPGA.

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SDRAM/FPGA

• Operate over system bus
• 8 bits for Address
• 8 bits for Data
• Chip Enable
• Read/Write Enable
• Clock
• IRQ

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Input/Output

• DSP means Digital Signal Processor, so we need a
  digital input and output.
• A/D converter translates signal into DSP.
• D/A converter translates signal out of DSP.
• DSP has Multi-channel Audio Serial Ports (McASP)
  to accomplish this, but it can also be
  implemented using parallel interface.

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Mixed Signal Interface

• Signal from Analog amplifier is fed to A/D
  Converter.
• Converts input voltage from analog signal in to
  Digital bit
• Synchronized with 44.1KHz Clock
• 16 Bit digital signal

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Mixed Signal Interface

• Digital to Analog (D/A) conversion methods
• Data is fed from DSP to D/A Converter.
• Standard D/A converters translate an array of
  digital bits into a bias voltage
• Synchronized with 44.1KHz Clock
• 16 Bit digital signal

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Power

• Regulated 3.3 and 2.5 V power buses from 9V DC
  adapter.
• 5V
• LCD
• 3.3 V
• Compact Flash
• A/D and D/A converters
• Data lines to and from FPGA
• 2.5 V
• FPGA Vcc

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Analog Signal Mixer

• A good recording mixer lets you route a variety
  of input signals and combine them into one
  signal.
• For a potential Add-on output signal from MP3
  player will mix with signal from D/A converter

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Audio Op Amps

• Analog signal from Mixer is going to be
  amplified and routed to speaker
• Amplifier is transistor based
• 1.6- to 3.6-volt speaker driver

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Field Programmable Gate Array

• Gateway of the user to all the other chips
• Controls the Clock to other devices
• Sends data to the DSP as well as the LCD
• Flash will set the FPGA through the DSP
• Program the FPGA through a JTAG Interface

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User Interface
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Schedule
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Division of Labor
Name Task
Nael Cassier User Interface/FPGA Configuration
Mason Stone DSP Integration
Tony Sawyer DSP Core Implementation
Henock Negassa A/D Component Integration
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Tentative Budget
Component Manufacturer / Part Number Estimated Price
Digital Signal Processor TI part TMS320C6713 100
FPGA Development Board Xilinx Spartan3 XC3S200 300
Flash Microcontroller Microchip PIC16LF74/P 60
Flash PROM Xilinx XC18V02 50
SDRAM Micron MT48LC16M16A2 50
A/D Converter TI ADS1625 60
D/A Converter TI 60
25 MHz Oscillator 40
LCD Display Crystal Fontz CFAH0802A 50
Printed Circuit Boards Advanced Circuits 200
Push-Button User Interface 45
Passive Components / Fixtures J.B. Saunders 200
9 V Power Supply J.B. Saunders 35
Analog Signal Mixer 100
Miscellaneous (printing/binding costs, posters, unforeseen parts, add-ons, etc) 250
Total 1600
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Possible Add-ons

• Add another analog signal (MP3)
• Amplifier Speaker
• Over Drive Circuit

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Risks and Contingencies

• Hardware Availability/ Damage
• Difficulties Implementing FPGA
• Difficulties Implementing LCD
• Difficulties With DSP Interface Bus

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Questions?