Guitar Effects ProcessorGuitar Effects ProcessorPreliminary Design ReviewPreliminary Design Review

September 9th, 2003September 9th, 2003

Groups Members:Groups Members:

Adam BernsteinAdam Bernstein

Hosam GhaithHosam Ghaith

Jasenko AlagicJasenko Alagic

Matthew Iyer Matthew Iyer

Yousef AlyousefYousef Alyousef

GoalsGoals

Provide a guitar effects generator Provide a guitar effects generator thatthat

• Has a user friendly interfaceHas a user friendly interface• Takes input from standard audio sourceTakes input from standard audio source• Produces output to standard amplifiers Produces output to standard amplifiers • Employs a modular design Employs a modular design • Produces real-time outputProduces real-time output• Can be programmed by userCan be programmed by user• Produces reasonably good audio qualityProduces reasonably good audio quality

Baseline ObjectivesBaseline Objectives

Working CPU (microcontroller, memory, Working CPU (microcontroller, memory, etc.)etc.)

Common interface between controller and Common interface between controller and all effectsall effects

Minimum of two working audio effectsMinimum of two working audio effects User interfaceUser interface Ability to program combinations/duration Ability to program combinations/duration

of effectsof effects Ability to adjust properties of effects (such Ability to adjust properties of effects (such

as intensity)as intensity)

Block DiagramBlock Diagram

MICRO-PROCESSING

UNITRAM

USER INTERFACE

MIXED-SIGNALINTERFACE

MIXED-SIGNALINTERFACE

MIXED-SIGNALINTERFACE

SIGNALPROCESSING

CIRCUIT(EFFECT 1)

SIGNALPROCESSING

CIRCUIT(EFFECT 2)

SIGNALPROCESSING

CIRCUIT(EFFECT 3)

AUDIOSIGNALINPUT

ROM

Digital Control SystemDigital Control System

Live adjustmentsLive adjustments Effect programmingEffect programming Effect driverEffect driver

Live AdjustmentsLive Adjustments

PC and/or keypad/button interfacePC and/or keypad/button interface Buttons turn effects on/off, control Buttons turn effects on/off, control

real-time parameters, and run real-time parameters, and run programs.programs.

Extension – Ideally, analog controls Extension – Ideally, analog controls such as light (photo-resistor), levers, such as light (photo-resistor), levers, and knobs will be provided to the and knobs will be provided to the user. These analog controls can be user. These analog controls can be mapped to any desired effect.mapped to any desired effect.

Effect ProgrammingEffect Programming

ASCII text file can written to program the ASCII text file can written to program the effects generatoreffects generator• Controls ramp/sweep of different effectsControls ramp/sweep of different effects

Program A sweeps Distortion effect from 0-100 Program A sweeps Distortion effect from 0-100 percent intensity in span of 5 seconds.percent intensity in span of 5 seconds.

• Program pre-set state of effectsProgram pre-set state of effects State A loads 50% Distortion, 20% Tremelo, and 80% State A loads 50% Distortion, 20% Tremelo, and 80%

WahWah

• Map buttons to functionsMap buttons to functions Example: Button1 will trigger Program A, Knob1 Example: Button1 will trigger Program A, Knob1

controls intensity of Effect3, Button2 loads State A, controls intensity of Effect3, Button2 loads State A, and so on…and so on…

Effect ProgrammingEffect Programming

Sample ASCII file:Sample ASCII file:state 0 : 0 128 1 64state 0 : 0 128 1 64[state 0] : [effect 0 50%] [effect 1 25%][state 0] : [effect 0 50%] [effect 1 25%]

program 0 : sweep 0 128 255 2000program 0 : sweep 0 128 255 2000[program 0] : [effect 0] [50%-100%] [2000 [program 0] : [effect 0] [50%-100%] [2000 milliseconds]milliseconds]

knob 0 : 1 0 3knob 0 : 1 0 3[knob 0] : [map to effect 1] [bits 0-3][knob 0] : [map to effect 1] [bits 0-3]

Extension: GUI application that helps Extension: GUI application that helps user write programs.user write programs.

Effect DriverEffect Driver

Sends control commands to Sends control commands to individual effectsindividual effects• Support for 2Support for 2nn effect modules, where effect modules, where nn is is

the number of address bitsthe number of address bits• k-k-bit messages sent on data busbit messages sent on data bus

Commands customized to control Commands customized to control parameters of each effect. parameters of each effect.

Example: DistortionExample: Distortion

Diagram of Effect DriverDiagram of Effect Driver

HC11 MICROPROCESSOR

KEYPADSERIAL PORT

EPROMRAM

RESET

FPGA

CLOCK

Mixed-Signal Interface Block Mixed-Signal Interface Block DiagramDiagram

MIXED SIGNAL

INTERFACE

DIP SWITCH ADDRESS ID

3 BIT LOGICAL

AND GATE(Implemented in FPGA)

LATCH

3 BIT ADDRESS BUS3 BIT ASSIGNED ID

LAT

CH

EN

AB

LE

DATA BUS

Mixed Signal InterfaceMixed Signal Interface

Digital to Analog (D/A) conversion Digital to Analog (D/A) conversion methodsmethods• Standard D/A converters translating Standard D/A converters translating

an array of digital bits into a bias an array of digital bits into a bias voltagevoltage

• Digitally controlled componentsDigitally controlled components

Digitally Controlled ComponentsDigitally Controlled Components

Determine the components in each Determine the components in each individual circuit that have the individual circuit that have the largest impact on the intensity of the largest impact on the intensity of the effecteffect

Devise specific interface scheme Devise specific interface scheme between data bits and analog between data bits and analog component valuecomponent value

Continuously update component Continuously update component value through interface scheme as value through interface scheme as data bits are passed on the busdata bits are passed on the bus

Xicor X9111Xicor X9111 Digitally Controlled Digitally Controlled

PotentiometerPotentiometer Turns on/off a series Turns on/off a series

of ~1000 gates of ~1000 gates moving a “Wiper moving a “Wiper Arm” up and down Arm” up and down the potentiometer the potentiometer altering the altering the effective resistanceeffective resistance

Xicor X90100Xicor X90100 Digitally Digitally

Controlled Controlled CapacitorCapacitor

Turns on/off Turns on/off numerous numerous capacitors in capacitors in parallel increasing parallel increasing and decreasing and decreasing the effective the effective capacitancecapacitance

Analog Signal Analog Signal ProcessingProcessing

Block Diagram of Signal Block Diagram of Signal Processing CircuitsProcessing Circuits

SIGNAL PROCESSING CIRCUIT

LOW PASS FILTER

SWITCHING MECHANISM

SIGNAL CONDITIONING

CIRCUIT

METAL STRUCTURE

MIXED SIGNAL INTERFACE

OUTPUT SIGNAL

INPUT SIGNAL

Requirements for Effect CircuitsRequirements for Effect Circuits

Input over-voltage protection Input over-voltage protection Ability to operate with DC power supplyAbility to operate with DC power supply Switch that turns on the effect or bypasses itSwitch that turns on the effect or bypasses it High input impedance unity-gain buffer to match the high High input impedance unity-gain buffer to match the high

output impedance of a guitar output impedance of a guitar Low pass filter to compensate for the high harmonics added Low pass filter to compensate for the high harmonics added

in the effects stages in the effects stages An output buffer to provide a low output impedance An output buffer to provide a low output impedance A level control allowing the adjustment of effect intensity A level control allowing the adjustment of effect intensity When bypassed, the effect is shorted without degradation When bypassed, the effect is shorted without degradation

of signal of signal LED indicating if the effect is on or offLED indicating if the effect is on or off Metal shield enclosing the circuit to eliminate noise Metal shield enclosing the circuit to eliminate noise

interferenceinterference

Effect CircuitsEffect Circuits

DistortionDistortion WahWah Other effects can be implemented if Other effects can be implemented if

time permitstime permits

Distortion Effect OverviewDistortion Effect Overview Distortion can be produced by clipping and/or Distortion can be produced by clipping and/or

compressing a sound wave. There two kinds of compressing a sound wave. There two kinds of distortion:distortion:• Harmonic: more ‘musical’Harmonic: more ‘musical’• Intermodulation: disturbing to the human earIntermodulation: disturbing to the human ear

Smooth edged clipping (soft clipping) produces Smooth edged clipping (soft clipping) produces more harmonic distortion than sharp edged more harmonic distortion than sharp edged clipping (hard clipping)clipping (hard clipping)

Objective:Objective:• maximize the harmonic distortion maximize the harmonic distortion • reduce intermodulation distortion. reduce intermodulation distortion.

Hard vs. Soft ClippingHard vs. Soft Clipping

Wah Effect OverviewWah Effect Overview

Mimics the sound of the word ‘Wah’.Mimics the sound of the word ‘Wah’. 3 ways to control:3 ways to control:

• ButtonButton• Program (Auto-wah)Program (Auto-wah)• PhotoresistorPhotoresistor

Wah Effect ImplementationWah Effect Implementation

The main component is a simple The main component is a simple resonatorresonator

The resonator acts as a band-pass The resonator acts as a band-pass filterfilter

The center frequency and resonance The center frequency and resonance (Q-factor) can be adjusted by the (Q-factor) can be adjusted by the user.user.

Wah EffectWah Effect

Order of EffectsOrder of Effects

1.1. VolumeVolume2.2. DistortionDistortion3.3. Tone controls Tone controls 4.4. Small time delays and Phasers Small time delays and Phasers 5.5. Longer time delays - chorus Longer time delays - chorus 6.6. Reverb and echo, etc. Reverb and echo, etc.

Courtesy of: http://www.geofex.com/effxfaq/fxorder.htmCourtesy of: http://www.geofex.com/effxfaq/fxorder.htm

ExtensionsExtensions

Extra effectsExtra effects Equalizer/Tone ControlEqualizer/Tone Control Computer screen displayComputer screen display Ability to program the Ability to program the orderorder in which in which

effects are appliedeffects are applied Superposition of different signalsSuperposition of different signals

Risks/Contingency PlanRisks/Contingency Plan

Noise resulting from analog signal Noise resulting from analog signal processingprocessing• Use low pass filters and metal structuresUse low pass filters and metal structures

Interfacing with Mixed-Signal Interfacing with Mixed-Signal componentscomponents• Add additional effect-side controlAdd additional effect-side control• Use standard D/A converters instead of Use standard D/A converters instead of

programmable componentsprogrammable components

Return on InvestmentReturn on InvestmentInvestment/Return Investment/Return

ItemsItemsAmountAmount

LaborLabor 5 EE’s * 225 hrs/EE * 5 EE’s * 225 hrs/EE * 20 $/hr = $22,50020 $/hr = $22,500

PartsParts $30/unit$30/unit

Cost of the UnitCost of the Unit $100$100

Profit on the unit w/o Profit on the unit w/o LaborLabor

$70$70

Units to break evenUnits to break even 321321

Division of LaborDivision of Labor

Tasks:Tasks: Done by:Done by:

Analog Signal Analog Signal ProcessingProcessing

Adam, Jasenko and YousefAdam, Jasenko and Yousef

Mixed-Signal Mixed-Signal InterfaceInterface

Adam, Jasenko, and Adam, Jasenko, and HosamHosam

MicroprocessorMicroprocessor Matthew, Yousef, HosamMatthew, Yousef, Hosam

Systems Systems IntegrationIntegration

EverybodyEverybody

Testing and Testing and Quality Quality

AssuranceAssurance

EverybodyEverybody

ScheduleScheduleID Task Name Duration

1 Initial Idea Proposal 6 days

2 Investigation Phase 6 days

3 Critical Design Review 6 days

4 Preliminary Design Review 20 days

5 Milestone 1 15 days

6 Milestone 2 15 days

7 Preliminary User Manual 6 days

8 Final User Manual 62 days

9 Technical Reference Manual 63 days

10 Analog Integrated Circuits 45 days

11 Mixed-Signal Interface 45 days

12 Create a CPU 45 days

13 Software Development 45 days

14 User Interface 25 days

15 Additional effects 12 days

16 System Integration 12 days

17 Testing and Quality Assurance 4 days

18 Internal Expo 1 day

19 Capstone Expo 3 days

Team

Everybody

Everybody

Everybody

Everybody

Eveybody

Everybody

Everybody

Everybody

Jasenko and Adam

Jasenko Adam and Yousef

Matthew, Hosam, Yousef

Matthew, Hosam, Yousef

Matthew

Jasenko, Adam, Yousef

Everybody

Everybody

13 16 19 22 25 28 31 3 6 9 12 15 18 21 24 27 30 3 6 9 12 15 18 21 24 27 30 2 5 8 11 14 17 20 23 26 29 2 5 8 11 14 17 20 23 26 29 1 4 7 10 13 16 19August 2003 September 2003 October 2003 November 2003 December 2003 January 2004

Questions?Questions?