1Spring 2002 EECS150 - Lec13-proj Page 1EECS150 - Digital DesignLecture 13 - Final Project DescriptionMarch 7, 2002John WawrzynekSpring 2002 EECS150 - Lec13-proj Page 2Project• Everyone will design, debug, and demonstrate a Music Synthesizer• Operation based on principle of waveform synthesisor sampling.– Sounds from recordings of real musical instruments arestored in memory then pitch-shifted and played back inresponse to note commands.• 1 or 2 partners/groupSpring 2002 EECS150 - Lec13-proj Page 3Digital Waveforms• In digital systems waveforms are represented as aseries of numbers, rather than a voltage or current, asin analog systems.– Example: sound waveform– Sound can be produced by sending series of numbers toDigital to Analog converter, then to Amplifier, then to speaker.– In principle any sound can be produced.Sampling rate: 31.25KHz16-bits per sampleSpring 2002 EECS150 - Lec13-proj Page 4Interfaces• MIDI: MusicalInstrument DigitalInterface.– Commands are sentfrom a keyboard (orcomputer) to controlthe synthesizer.• Waveforms are storedin the ROM (read onlymemory).• Monophonic: onevoice at a time.Spring 2002 EECS150 - Lec13-proj Page 5Theory of Sound and Music• Air vibrating in the frequency range of 20Hz to 20KHz isperceived as sound.• The three important characteristics of perceived soundare:– loudness (relates to amplitude)– pitch (relates to frequency)– timbre (relates to shape)• Human hearing is approximately logarithmic inperceiving loudness and pitch:– we perceive the loudness as being prop to the log of the soundwave amplitudeSpring 2002 EECS150 - Lec13-proj Page 6Timbre• tone quality or “color”• Different instruments have different timbres.• We perceive timbre based on how a note begins, repeats,and ends.• For many instruments a simple model can be used torepresent the shape of the waveform.– Attack, sustain, release (decay)• Works best for “driven” instruments: woodwinds, brass,bowed strings.• Pluck and struck instruments don’t have the “sustain”[picture]2Spring 2002 EECS150 - Lec13-proj Page 7Pitch• Middle C has frequency of261.63Hz.– MIDI encoding of “60”• High C (an octave above middleC) has frequency 523.25Hz– MIDI encoding of “72”• Other tones can be produced bymultiplying and dividing thefrequency by factors of 12th rootof 2.• Pitch:– 12 semi-tones form thechromatic scale of the westernscale.– To move from one up to thenext:• freqnext = freq * 12th root of 2.– After 12 such multiplications wewill have doubled the freq andreached the octave.• Most people can detect pitchdifferences as small as a fewhundreds of a semi-tone (or afew times the 1200th root of 2)!Spring 2002 EECS150 - Lec13-proj Page 8 Spring 2002 EECS150 - Lec13-proj Page 9Playing Notes• ROM used to store notes has limited capacity.• For notes with “sustain” portion, would like to vary note durationSpring 2002 EECS150 - Lec13-proj Page 10Pitch ShiftingSpring 2002 EECS150 - Lec13-proj Page 11Pitch ShiftingSpring 2002 EECS150 - Lec13-proj Page 12Linear Interpolation3Spring 2002 EECS150 - Lec13-proj Page 13ROM (EEPROM) Layout• One stored note per instrumentis never enough.– Timbre varies from note tonote over the range of theinstrument.• ROM holds directory with oneentry per MIDI note number.• Entry holds pointer to note“template” and “step size”.• Note step sizes areprecomputed (synthesizerdoes not need to do 12th rootof 2 calculation.• One instrument per ROM(might change this later).Spring 2002 EECS150 - Lec13-proj Page 14Directory Entry Layout• 20-bit template pointer • 12 bits of “step size”Spring 2002 EECS150 - Lec13-proj Page 15Template LayoutSpring 2002 EECS150 - Lec13-proj Page 16Instrument Template Files• We will provide you with template files and a program forconverting these to EPROM format.• We also have programs for taking instrument samples fromstandard file formats and converting them to our templateformat. You are encouraged to generate your owntemplate files and EPROMs.• We might extend the format (and project) to allow for morethan one instrument per EPROM.– Switch among the instruments either through dip switches or MIDIcommands.Spring 2002 EECS150 - Lec13-proj Page 17High-level Block DiagramThis is only a suggestion. Your organization is up to you.FSM and datapathfor each block.Spring 2002 EECS150 - Lec13-proj Page 18Checkpoints3/11 UART Design and Test3/18 ROM Interfacing3/25 Recess4/1 MIDI Interface4/1 Audio Stage4/8 Monotone Notes4/15 Notes of Arbitrary Frequency4/22 Velocity Sensitivity4/29 Spare5/6 Final Checkoff• Your are strongly suggested towork ahead.• These are only minimumrequirements.• Completion of checkpoints arepart of your project grade.• Project spec document onlinetoday.• All checkpoint write-upsavailable in next couple days (indraft form).4Spring 2002 EECS150 - Lec13-proj Page 19Extra Credit• Early Final Checkoff.– 1 week or more• Low CLB Count.– “low” quantified later• Interpolation– add linear interpolation forsample lookup• Polyphony.– The ability to play multiple keysat once• Velocity Sensitive TemplateLookup.– Index templates not only on keynumber but also velocity.• Extra credit only considered forfully functional designs.• Point assignment announcedlater. Usually in the 15% range.Spring 2002 EECS150 - Lec13-proj Page 20 Spring 2002 EECS150 - Lec13-proj Page 21ConnectionsSpring 2002 EECS150 - Lec13-proj Page 22 Spring 2002 EECS150 - Lec13-proj Page 23 Spring 2002 EECS150 - Lec13-proj Page 24Note On5Spring 2002 EECS150 - Lec13-proj Page 25Note offSpring 2002 EECS150 - Lec13-proj Page 26Keyboard MappingSpring 2002 EECS150 - Lec13-proj Page 27Spring 2002 EECS150 - Lec13-proj Page 28“Running Status”• The MIDI standard convention allows a transmitter tocompress the data stream by dropping status bytes.• A command without a status byte implicitly uses whateverstatus byte was most recently sent.• Therefore a keyboard can send a sequence of note-on andnote-off commands only the first of which having a statusbyte.• Your synthesizer must conform to the running
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