Camosun College Audio Effects Processor
Contents
1. 1 2 3 5 6 5V D D 1 IkOhm ce ON O 1uF P ux OSCUCLEIS OSC2CLKOUT TH ry MCIR V RCOTIOSOMTICKI 3 4 aay RAO RCUTIOSUCCP2 TS AY gCD RS RAI RCUCCPI Eras pi ae RA2 RC3 SCK SCL SARS slim AE RAS RCASDISDA4 53 D SCD ores rcp i 2 RAWTOCKI RCSISDO4 1a a2 0LCD RS RAS SS RCGTX CK LAD WR 93 03 LCD RD RBUNT O RCURXIDT AD BWR 4 fos cowe RBI RDO PSPO TADS 95 0s D0 RB2 RDI PSPI Sp 96 06DI RB3 RDO PSP2 S ADHI 7 07D2 RBS RD3 PSP3 SHAN 2 8 08 D3 RBS RDAPSPA TL AD 99 09D4 c 2090 RB6 RDS PSPS S A 10 10D5 c BSR Ip SETS DSPRESETS O REQRD ANS2 _RDT PSPT 912 12D7 REIWR ANG gt REYCS ANT D e TC xg 13 BUSY S R 5V PICTOFS74 20 P 40 5V omg 14 RESET pd A r 15 isser EI 16 16V E vant 17 17 GND 18 18 Vdrive RRE Our lt 19 19GND d dian i 5 1 20 20 Vbackligh 581 ax SWI meor Cs 3 GNDVDD 7 3105 WC 3 00 2 Hos ADSAOO 3PBSW2 3 sm 2PBSWI 2 T n n 1 GND 1 o EE al di ban Optical Switth 221 apa QUUD pda m a ed ano Paps EN Par 1ADS 47 h AD B g do op DD do 19 pA B 6 8 AID pp AT TADS 19 PADI O 1uF Uj d13 14p AB TADIL o 13 14 p TADI2 13 D8 9 Sv AD o TADIA Do gt I5 16 bX ARE IS 16 1 DI 17 18p X 17 18 y D 5010 xl 2 TACKS 17 18 PAL ps DN dal bs TS 21 22 p WR us Di spa dS po2. Tempered Scale Ratio Interval Name Just Interval Chromatic Version C 1 0000 Unison 1 0000 C 1 0595 Half Step 1 0667 D 1 1225 Whole Step 1 1250 D 1 1892 Minor Third 1 2000 E 1 2599 Major Third 1 2500 F 1 3348 Perfect Fourth 1 3333 F 1 4142 Diminished Fifth 1 4063 or 1 4222 G 1 4983 Perfect Fifth 1 5000 G 1 5874 Minor Sixth 1 6000 A 1 6818 Major Sixth 1 6667 A 1 7818 Minor Seventh 1 8000 B 1 8877 Major Seventh 1 8750 C 2 0000 Octave 2 0000 Table 1 The scale The 12 tone equal tempered scale is a natural scale for electronic music systems because of the simplicity of equal valued steps Though nearly impossible to audibly notice any difference the musician must acknowledge this is only an approximation of the true Just Major Scale 11 2 4 9 Fierce Filter To reduce high frequency noise from a particular input instrument the Fierce Filter allows the user to remove high frequencies The User is also able to set the cut off frequency 12 2 5 Cost DSP Board 132 00 Provided PIC 15 00 Provided SRAM 32 00 Flash 10 00 Free PCB 10 00 Provided Connectors 15 00 LCD 50 00 Knob 32 00 Buttons 10 00 Case 22 00 Misc 20 00 Sub Total 348 00 Provided 167 00 Total 181 00 We completed this project significantly under budget This is due to most of the expensive components supplied by the College 3 0 CON
3. distortion 14 dB decibel Dry Signal Filter Line Signal Mic Microphone Signal Wet Signal a unit of measurement ratio of two voltages dB 20log V1 V2 no processing of the input signal device or program for adding or removing part of a frequency bandwidth amplified signal within 100mV peak to peak produced by sound cards turntables etc signal within 20mV peak to peak produced by guitars microphones etc signal with effects added 15 5 0 REFERENCES 1 Analog Devices ADSP 2100 Family EZ KIT Lite Reference Manual Norwood MA 1995 2 Analog Devices ADSP 2100 Family EZ KIT Lite Evaluation Platform Data Sheet Norwood MA 1998 3 Behringer International DX500 Pro Mixer USER S MANUAL Hanns Martin Schleyer StraBe D 47877 Willich M nchn ide September 1998 4 Hutchins Bernie Music for Electronic Engineers Electronotes Ithaca New York July 1975 5 Orfanidis Sophocles J Introduction to Signal Processing Prentice Hall Signal Processing Series Upper Saddle River New Jersey 1996 16 6 0 6 1 APPENDICES Schematic
4. pedals have hundreds of effects with fantastic customizability but their price is beyond the amateur guitarist s budget That is not the only problem What about people who play the flute oboe or saxophone What about DJ s using turntables There are many instruments beyond guitar that can use an effects processor The User only requires only a microphone and preamp The Camosun College Audio Effects Processor improves the sound of any instrument 2 0 DISCUSSION 2 1 Product Description This unit has stereo input and output channels a Power Connector Port simple controls and many customizable audio effects enclosed in a beige case 1 4 Output Port 1 4 Input Port Power Connector Pot 7 LCD Presets Graphical Display Control Knob 7 Figure 1 Physical Layout 2 2 Hardware The entire Camosun College Audio Effects Processor consists of four parts 1 ADSP 2181 EZ Lab demo board from Analog Devices 2 PIC16F877 Microcontroller from Microchip 3 Various User I O devices 4 Control components 2 2 1 ADSP 2181 EZ Kit Lite The ADSP 2181 EZ Kit Lite is a powerful inexpensive evaluation platform for the ADSP 2181 DSP We chose this platform due to its on board AD1847 SoundPort CODEC This is a full duplex 16 bit stereo CODEC capable of sampling at 48 kHz ideally suited for our project Unfortunately this part is no longer in production therefore we could not produce a commercial produ
5. stepping is looping a variable around zero Stepping from 255 to zero and backwards seems more efficient than blocking the User at the maximum value However if turning the knob quickly the User may pass a desired maximum value To stop this we turn OFF velocity controlled stepping when the User is 20 steps from minimum and maximum values This way the User can still loop around but not make an undesired mistake 2 2 3 3 Presets To allocate the musician s favorite effects to particular presets we use four Preset Buttons These presets are simple Normally Closed N C contacts The reason for these particular buttons is they are both inexpensive and esthetically pleasing they already have red buttons 2 2 4 Components There are a few more parts of this processor Power Connector Port Stereo input output jacks AD8400 Digital Potentiometer 74HC138 Address Decoder K6T4008C1V 512kbyte SRAM Power Connector Port Since the processor consumes a substantial amount of current to provide ultimate sound clarity it is not efficient to run this unit from batteries Simply connect the included power adapter to the Power Connector Port and you are ready to play Stereo input output jacks The audio input and output ports are 14 stereo jacks 14 jacks are a standard in the music industry for their power handling abilities and cost of cable AD8400 The AD8400 is a single 256 step digital potentiometer used for
6. these timers in this project is to determine timeouts when waiting too long for a particular device to respond and to determine the rotation speed of the Control Knob 2 2 3 Input Output devices The Input Output devices consists of three groups 1 LCD Display 2 Control Knob 3 Preset Buttons Please refer to section 2 3 User Interface and Interaction for more information regarding the use of the Camosun College Audio Effects Processor 2 2 3 1 LCD Display The LCD for this project is the Optrex DMF50834 with a built using the NEC upd16435 controller distributed by Apollo Displays www apollodisplays com This product is ideal for this project for its multiple options and fast speed Some of the built in functions are Reverse Line Magnification Double width double height or both double width and double height Blinking character Cursor Backlight At the beginning of the project the options were unknown this made this LCD particularly advantageous We considered using the backlight function but abandoned it because of its extreme sensitivity to small changes in voltage In addition the LCD for this project was inexpensive because of a broken backlight To signify a selected item we used the reverse line function Our group felt this would unmistakably designate a selected item The Graphical Display shows the User the vertical menu system and all sub menus This system is unbelievably U
7. to program space restrictions 2 4 4 Rad Reverb Reverb is simply a Comb Filter This effect occurs when a sound wave bounces off walls of a listening space but has an interesting effect when there are multiple reflections 2 4 5 Phun Phasor Phasing or phase shifting passes the signal through a narrow notch filter and combines a proportion of the filter s output with the direct sound To create a weird effect the centre frequency of the notch filter varies in a controlled manner The User sets this variable in the Phun Phasor Sub Menu 2 4 6 Funky Flange 10 The process of periodically varying the delay with a low frequency such as 1Hz is the Flange effect This product allows the User to set both the period and the frequency of this sound 2 4 7 Demon Delay Delay for our processor is really a tapped delay which is really just a set of delays Our system provides up to three separate delays of a signal at different gains The User sets both delays and gains for the three taps This allows plenty of variables for the musician to customize their sound 2 4 8 Power Pitch The Power Pitch allows the User to bend the input signal in half step intervals up to one octave up or one octave down An octave consists of 12 half step tones to create the Equal Tempered Scale The scale based on fifths proposed by Pythagoreas 600BC is the basis of the Equal Tempered Scale Equal
8. CLUSION The Camosun College Audio Effects Processor provides the musician with several advantages over many other similar products Line input Not only for guitar Extremely simple User Interface with clear LCD display and few buttons Future expandability This chief disadvantage of this product is only in the number of effects Future expansions of this product will allow for multiple inputs and more effects 13 4 0 GLOSSARY of TERMS HARDWARE CODEC the unit Full Duplex Input Device LCD Output Device Power Connector Port Preset Buttons MENU SYSTEM Main Menu Sub Menu AUDIO TERMINOLOGY Clip Clipping Hardware that performs analog to digital and digital to analog conversion Includes signal conditioning circuitry 3 Control Knob large knob below the LCD This is the main input device for the User Control Knob Button asserts when the Control Knob is pushed into Control Knob Rotation turning the Control Knob The ability to record and playback simultaneously Any audio source with a LINE output The text display screen Any audio output device with a line input ie Amplifier Requires minimum 7V at 200mA power adapter Four red buttons to allocate particular effects to particular Presets The vertical list of particular options and effects The options for a particular item in the Main Menu Sub Menus are only for items containing options or information overload severe
9. DA A A19 I9DI3 d CAP pil ee E 074 0 Ds obi 1308 3 xb pn 3 wx 202 lg y D6 zo 27 28bX i003 og DS From 14 D9 Dis 39b DE COP 5 15DI0 2 Als C 5 31 3238 Xs px 33 34 X33 34 p lt 19DI3 3 36 moro 20Di4 2L DIS 40 39 40b 2 2 a ap 44 54 46 45 46 48 47 4 Ind 2 49 50 49 50 HEADER 255 HEADER 25X2 Our ISRAMIGSg A RD o o A WH Z FOLIO Nine lt ee upaDupa Audio Processor Sue Number Revision B i Date 21 Mar 2001 Sheet of File C Documents and Settings dgarpioriitpocuments ETiects Pres 1 2 3 5 6 17 6 4 User Interface Top Level State Machine INITIALIZE Display Effects Menu with selected effect first Preset Button Rotation Butt Button Increment or m pur Played associated decrement selected effect selected item Display selected Rotation Sub Menu Preset Button Increment or Associate current decrement Button effect to Preset Button selected item P teke selected T Preset Button Rotation Button Increment or Associate current Men effect to Preset Button variable 20 6 5 User Interface Controller Source Code See hard copy 21 6 6 DSP Source Code See hard copy 22
10. ELEX 290 Camosun College Audio Effects Processor Prepared for Godfried Pimlott Joe Benge Prepared by Darryl Gamroth Simon Tipler March 10 2001 March 16 2001 Godfried Pimlott Joe Benge Camosun College Dear Mr Pimlott and Mr Benge I am enclosing our report Camosun College Audio Effects Processor as requested Sincerely Simon Tipler Enc Executive Summary The Camosun College Audio Effects Processor allows the User to easily add effects to their music or clean a noisy signal With a simple User Interface and many effects with extreme customization features this processor surpasses the competition Using a DSP processor all mathematical calculations are very quick to render pristine sound quality Also the User Interface is ridiculously simple with a clear graphical display and a single Control Knob with push button This knob controls all variables and navigation allowing the musician to make quick changes and get back to enjoying their music Table of Contents 10 CONCEPT ai A A bando 1 1 1 Understanding this Repottaus i eseeeii cra disparate 1 1 2 Background cuc eet ae b VE ELO e des ex Era wa wer Viae d bed da 1 2 0 DISCUSSION is A facis UNE e 2 2 1 Product Description iiie dens e i aate doves ux ea p nU EE nr ae 2 24 ATINA eee 2 2 2 1 ADSP 2181 EZ Kite ci rekker 2 2 2 2 PIC Microcontroller ous iaa 5 2 2 3 Input Output devices Leere ceret ohh ern noh 6 2 2 3 1 ECD Displ
11. ay ati ovS EE RUF ME PESE Ext VEM Ud ge 6 2 2 3 2 Control Knob ia A iaa 7 2 2 3 3 PRO A tae awa CN ED pb 8 2 2 4 Components rico ai ea 8 2 3 User Interface and Interaction c cc cece cece cece ee ceecccceeesceeeees 9 24 Effects reco rro ERR FER cide ceietankectcauenddeves ERR PREX PO ERE VE ETES 10 2 4 1 PASSER FUN ad Utama posa en 10 2 4 2 Dirty Distortion soe ciet terrere ER eo shane Goods bres rau peo 10 2 4 3 CO Lo NE 10 2 4 4 Rad Reverb ii deklarere rede 10 2 4 5 Phun Phase ua an i ba Guan xta ox Oba eve VO a 10 2 4 6 Funky Flange or coei cei use exec ken teo eoe uen ha daa se costa EA 10 1 4 Demon Delay cosi ter Ure Eos b EU COR BER VERO FLA ER VENETA ORAN 11 2 4 8 Power Pc vara CIA 11 2 4 9 Herce Fe Lua aii ata 12 PA MEE Terese 13 3 0 CONCLUSION ur etse EV Eae ee de de i t e e PVC E A A 13 ZU GLOSSARY of TERMS ST 14 50 REFERENCES ee 16 6 0 APPENDICES Suhrs seene eara ere 17 6 1 SchieablC acer RI vedere AA ERE E UR 17 62 Top Layer PCB 3 e sik ep REUNIR ERRERO REOR ahead ss Bee Sa oes 18 6 3 Bottom Layer PCB scr 19 6 4 User Interface Top Level State Machine eeeueueee 20 6 5 User Interface Controller Source Code cc cece cceeeeeeeceeeeees 21 6 6 DSP SOURCE Code ae 22 List of Figures Figure 1 Physical Layout ciu vs e brt E AA 2 Figure 2 Effects Building Blocks oooooorooroccrnonocconorconoccororcoranas 3 Figure 3 Delay Effect ii sagd
12. ct using this part The ADSP 2181 is a 16 bit fixed point digital signal processor running at 33 MHz it is adequate for our current incarnation of the effects processor but has several quirks All of the effects are processed in the time domain As all effects are time based they each share the same fundamental building blocks The base block for the majority of the effects is the delay line The delay line puts an input sample into memory which is recalled later to produce a delay To create reverb we feed the output of the delay back into its input which causes an echoing sound This echo will continue forever if the gain is equal to one Delay by D 70 Add samples v Variable Delay Multiply Gain x Figure 2 Effects Building Blocks All effects are constructed using these building blocks as shown below x n 2 gt y n x n ax n d A Za 4 Figure 3 Delay Effect A x n A y n x n ay n d Figure 4 Reverb Effect x n lt p gt y n x n ax n d n A 7 Z din d n Figure 5 Chorus Flange Pitch and Chord Effect As shown in Figure 5 Chorus Flange Pitch and Chord Effect we can modify the function d n as we see fit In the chorus effect the processor varies the delay from 20ms to 50ms at 0 25Hz Flange is just a special case of chorus delay varies from Oms to a user sp
13. e TEE nna nh e 3 Figure 4 Reverb Efectuar ias 4 Figure 5 Chorus Flange Pitch and Chord Effect eeeeeeeeeeeee 4 Figure 6 Modulator used for Vibrato and Distortion oooococccccocommmmmooo 4 Figure 7 Phasor using a variable frequency notch filter oooooooomoooo 5 Figure 8 Direction state machine for the Control Knob 7 List of Tables Table 1 The scale Camosun College Audio Effects Processor 1 0 CONCEPT This report will introduce the reader to the Camosun College Audio Effects Processor including descriptions of the unit input output requirements User Interface and controls and the effects 1 1 Understanding this Report The simple menus system accesses all of the options for this system To further understand the navigation system read the Camosun College Audio Effects Processor USER MANUAL When this report describes the use of each effect we assume the reader is familiar with the basics of musical terminology The Glossary of Terms includes definitions of most terms in this report 1 2 Background Guitar effect processors are commonplace in the music industry with nearly all guitarists using some type of guitar pedal to alter the sound from their guitar Since the 60 s guitar pedals have improved with better sounds and more options for the musician Leaders in this huge industry include BOSS Digitech Ibanez and others Currently multi effect
14. ecified amount and a selected frequency Pitch scaling is a similar technique except to drop and add samples to the playback buffer we use saw tooth waveform x n X E y n 2 ax x n x f n fn Figure 6 Modulator used for Vibrato and Distortion Distortion is achieved by modulating the input signal with either a sinusoid or a saw tooth wave The output signal can be saturated by adjusting the gain x n 2 gt y n A Figure 7 Phasor using a variable frequency notch filter To implement phasor the input signal is mixed with itself passed through a notch filter This causes a phase shift in the output signal 2 2 2 PIC Microcontroller The PIC Microcontroller from Microchip controls all User input and transmits all changes in data to the ADSP EZ Lab demo board The User Interface uses the PIC16F877 for its multiple serial communication ports speed many input output ports built in timers and availability of optimized C compilers For this project we use the Serial Peripheral Interface SPI to communicate with a digital potentiometer the Analog Devices AD8400 discussed in the Control Components section The PIC also runs at the maximum speed of 20MHz By running at this speed the PIC can quickly compute calculations rapidly transmit data and control many devices Since current consumption is not a variable in this project because of the required power adapter this warrants running at a
15. ect the effect in the Main Menu and press the chosen Preset Button Immediately this effect processes the input signal To vary the sound enter that particular menu item and change the variables The effect updates the sound in real time This allows the musician to create very interesting sounds To overwrite a particular preset simply select a new effect and press the same Preset Button Right away the new effect will be associated with that Preset Button and the unit will immediately run the new effect For more information on User Interaction please refer to the Camosun College Audio Effects Processor USER MANUAL 2 4 Effects 2 4 1 Passthru Simply outputs the input signal with absolutely no processing on the sound This is called a Dry Signal 2 4 2 Dirty Distortion By increasing the amplitude of the input signal eventually the signal will clip Clipping is the process by which an AC signal increases past the stability point The result is many high frequency components also known as noise The User has full control over the level of noise 2 4 3 Cool Chorus The Chorus effect allows the user to hear multiple instances of the input signal when each instance synchronizes with the others except for small variations in their strength and timing This means that one vocalist can sound up to three people singing the same thing The User controls the number of voices heard with a maximum of three due
16. faster speed Since this PIC16F877 has 33 I O pins there are enough data lines for the parallel memory write control User input and chip selection Originally there were not enough data lines for communication To resolve this problem the Toshiba TC74HC595 SPI 8 bit shift register could add eight more output lines This device is incredibly useful because it only requires a chip select and the SPI data and clock lines which the digital potentiometer already uses After much rearrangement and a change in a major component this chip was no longer necessary Another purpose for the PIC Microcontroller is the Interrupt on change feature on PORT B for the Control Knob We tested this feature however polling proved to be more effective Using the Interrupt on change missed occasional step rotations but polling never missed any changes To compose code for the PIC16F877 we used the PCM C Compiler This compiler is extremely efficient and it is simple to use for writing strings of data to a device To fit large programs this compiler spends most of the compiling process rearranging code to fill banks on the PIC Most compilers for PIC do not rearrange segments for optimum banking To make compiled code more efficient the complier optimizes both delays and complicated math routines Another feature of the PIC processor family is the built in timers These allow interrupts to occur determined by the programmer The purpose for
17. ser friendly to navigate and edit settings A reversed line designates the currently selected item on the LCD Depending on the lighting in the environment the User is able to digitally set the contrast in the Contrast menu item see AD8400 in the Control Components 2 2 3 2 Control Knob To simplify all User interaction the knob with integral push button controls the entire system We chose a 32 detent Grayhill 61C11 01 08 02 The detents provide the User feedback to acknowledge single steps There are only three wires to communicate to the PIC controller two wires for the direction of rotation and the other wire provides the signal for the push button LEFT SER RIGHT S1 Figure 8 Direction state machine for the Control Knob Since the PIC recognizes each step of the Control Knob it is simple to determine the speed and direction of the rotation Using one of the PIC s built in timers we determined that a change within 190ms defines fast rotation Any changes that take longer than this define as slow or single step rotations We call this process velocity controlled stepping where fast rotations result in bigger changes in setting a variable Steps for a fast rotation are groups of ten With a 32 step knob a full byte change is 256 10 32 0 8 of a full rotation We chose groups of ten because this is the greatest change possible for one to easily rotate the knob The problem with velocity controlled
18. the contrast of the Graphical LCD This part communicates using the SPI port allowing extremely fast changes This allows the User to digitally set the contrast of their screen in the Contrast sub menu We researched other digital potentiometers however the Analog Devices series provides different ranges 32 step 64 step 128 step and 256 step For contrast many steps are required to achieve optimum contrast Also SPI communication is extremely simple and fast for a PIC Microcontroller 74HC138 The 74HC138 address decoder splits the DSP s 4MB addressable space into eight blocks of 512 kB One decoder output selects the flash memory and another selects the 512k of SRAM We used this part rather than other address decoders simply because we used this part in studies at school K6T4008C1V The K6T4008C1V from Samsung is low power high speed SRAM SRAM is required to provide a sufficient buffer for the digital data from the input signal The reason for SRAM opposed to other high speed volatile storage is that our DSP requires SRAM 2 3 User Interface and Interaction The entire interfaces consists of three parts 1 Graphical Display 2 Control Knob 3 Four Preset buttons To enter a menu item edit a number exit number entry etc simply press the Control Knob into the unit This way speed of entry is extremely efficient and the User does not have to search for multiple buttons To define a particular preset simply sel
Download Pdf Manuals
Related Search