1-bit Audio and the Arduino David J. Zielinski Overview 1. - - PowerPoint PPT Presentation

1-bit Audio and the Arduino

David J. Zielinski

Overview

• 1. Terminology of Sound
• 2. Atari 2600
• a. clock division frequencies
• b. linear feedback shift registers
• 3. Arduino Uno
• a. Specifications
• b. Audio Generation Methods
• c. Code Examples and Demos
• d. Arduino Due
• e. Future Work

sound waves are oscillations in air

• pressure. The amplitude (viewed on y axis)

is proportional to the change in pressure 1 = Peak amplitude 2 = Peak-to-peak amp 3 = RMS amplitude 4 = Wave period

loudness is the perceptual sense of amplitude. quiet vs loud frequency is the number of repeating events per unit time. pitch is the perceptual sense of frequency.

bit depth is seen as quantization on the y axis

Retail availability 1977 Introductory price 199 USD Units sold 30 million CPU MOS 6507 @ 1.19 MHz Memory 128 bytes RAM, 4 kB ROM

Atari 2600

• MOS 6532 (RIOT) Ram-I/O-Timer
• MOS 6507. Smaller/Cheaper version of the 6502

(used in Apple, Atari, Commodore)

• Television Interface Adaptor (TIA)

Atari TIA Chip

• non-frame buffer design!
• reading input controllers
• sound effects

○ 2 independent noise generators ○ 5-bit frequency divider ○ 4-bit audio control (sets waveform) ○ 4-bit volume control

Jay Glenn Miner (May 31, 1932 – June 20, 1994) was a famous American integrated circuit designer, known primarily for his work in multimedia chips and as the "father of the Amiga". Lead developer of the TIA chip.

String/Tube Resonance Pitch Perception

100 hz - root 200 hz - octave 300 hz - 5th 400 hz - octave 500 hz - Major 3rd 600 hz - minor 3rd

• ctave: 200/100

2 2 5th: 300/200 3/2 1.5 4th: 400/300 4/3 1.33_ Maj3: 500/400 5/4 1.25 min3: 600/500 6/5 1.2 6th: 500/300 5/3 1.66_

C C# D D# E F F# G G# A A# B C blue = equal temperament red = just intonation pitch freq ratio

• ne reason classic video games

sound distinctive is the utilization of the clock division technique which results in a scale based on the undertone series.

blue = just intonation red = harmonic undertone cents Pitch

Gioseffo Zarlino (1517-1590) was an Italian music theorist and composer of the Renaissance.

First proposed the idea of the undertone series.

Hermann Ludwig Ferdinand von Helmholtz (1821 – 1894) was a German physician and physicist who made significant contributions to several widely varied areas of modern science.

Argued that sympathetic resonance is at least as active in under partials as in

• ver partials

Harmonic Undertone Demo

http://jackaudio.org/

4 bit poly, 5 bit poly, 9 bit poly

XOR (exclusive or)

A B Output 1 1 1 1 1 1

Linear Feedback Shift Register

Poly4: Taps at 2 and 3

1 0 0 1

• utput: 1

Now

1 1 0 0

Future

Demo of LFSR Poly4: taps at 2,3 Poly5: taps at 2,4 Poly9: taps at 4,8

Arduino Uno

Flash / Program Memory 32 KB SRAM / Variable Memory 2 KB Clock Speed 16 MHz 5v $30

Why arduino?

• low cost. leave installed for installation.
• input: knobs, switches, pressure sensors,

accelerometers, ultrasonic distance, temperature, capacitive sensing.

• output: usb, control motors, lights, and audio
• making things is more fun then buying things
• open source hardware/software
• manufactured in Italy
• subset of C++

Where can you get it (and components)?

In Person: Radio Shack [northgate mall] Hobbyist: sparkfun.com adafruit.com Pro: digikey.com newark.com

Methods of Running

• With a computer. Use arduino to read input,

then send via serial message (via USB cable) to computer for further action.

• Stand alone. Arduino reads input and does

any processing on board.

Methods to Generate Audio

Type Pro Con tone function call

• part of standard libraries.
• pitch is accurate.
• monophonic (1 pitch at a

time).

• square wave only.

add on shield

• actual audio output (24bit, 44k).
• arduino uno processor is

too slow.

• shield costs $$

pin toggle in main loop

• generate arbitrary 1-bit waveforms.
• polyphonic (multiple pitches).
• simple programming
• 1-bit waveforms
• pitch not accurate
• highest pitch limited by

amount of processing pin toggle in interrupt

• generate arbitrary 1-bit waveforms.
• polyphonic (multiple pitches).
• pitch is accurate
• 1-bit waveforms
• complicated programming
• need buffer = latency

Things you will need:

How does electricity work?

How to convert 5v to 0.45v ? Solution: voltage divider

What does this look like?

Pitch Linear

void loop() { int v = analogRead(A0); int v_half=v/2; if(current_sample<v_half) digitalWrite(2,HIGH); else digitalWrite(2,LOW); current_sample=(current_sample+1)%v; }

Pitch Exp

void loop() { int v = analogRead(A0); int vp=int(pow(v,2.0)/5000.0); int v_half=vp/2; if(current_sample<v_half) digitalWrite(2,HIGH); else digitalWrite(2,LOW); current_sample=(current_sample+1)%vp; }

samples input value

Noise

void loop() { int v = analogRead(A0); int vp=int(pow(v,2.0)/5000.0); if(current_sample==0) { int val=random(2); if(val==1) digitalWrite(2,HIGH); else digitalWrite(2,LOW); } current_sample=(current_sample+1)%vp; }

Dual Pitch

void loop() { int v = analogRead(A0); int v2 = analogRead(A1); s1.set_freq(v); s1.tick(); s2.set_freq(v2); s2.tick(); }

AND aka Ring Mod

void loop(){ int v = analogRead(A0); int v2 = analogRead(A1); s1.set_freq(v); s2.set_freq(v2); int d=s1.get_val(); int d2=s2.get_val(); byte f=d&d2; digitalWrite(2,f); }

A B Output 1 1 1 1 1

XOR aka Korg MS-20 Ring Mod

void loop(){ int v = analogRead(A0); int v2 = analogRead(A1); s1.set_freq(v); s2.set_freq(v2); int d=s1.get_val(); int d2=s2.get_val(); byte f=d^d2; digitalWrite(2,f); }

A B Output 1 1 1 1 1 1

byte val=pgm_read_byte_near(pos); if(val>128) digitalWrite(2,HIGH); else digitalWrite(2,LOW); pos++; if(pos>pos_end) pos=start_pos;

Program Material

Decimation Delay

byte val=delay_array[d_pos]; int prob=random(0,1024); dv=(val>0 && prob<decay) || pbyte; delay_array[d_pos]=dv; d_pos=(d_pos+1)%dtime; digitalWrite(3,val); digitalWrite(2,pbyte);

Looper

if (sensorVal>0) {

pbyte=pitch_sample<phalf; triggered=true; } pitch_sample=(pitch_sample+1)%pmax; byte val=delay_array[d_pos]; if(triggered) delay_array[d_pos]=pbyte; else delay_array[d_pos]=val; d_pos=(d_pos+1)%dtime; digitalWrite(2,pbyte); digitalWrite(3,val);

Arpeggiation

byte notes[6]={1,2,4,8,4,2}; int vpn=sensor_val*notes[current_note]; int v_half=vpn/2; digitalWrite(2,current_sample<v_half); current_sample=(current_sample+1)%vpn; note_sample++; if(note_sample>samples_per_note){ note_sample=0; current_note=(current_note+1)%6; }

Arduino Due

Due Uno Clock Speed 84 Mhz 16 Mhz SRAM (Variables) 96 KB 2 KB Flash (Program) 512 KB 32 KB Voltage 3.3v 5v Analog Input 12 [12 bit] 6 [10 bit] Analog Output (D/A) 2 Digital Pins 54 14 Price $50 $30

Guitar Effect Pedal

Active Paintings

Skull Drum and Leg- Tar

P10 Project 100, 1k, 10k, ... channel installation

Thank You!

Wet Ink Ensemble @ Casbah 8pm featuring Kenneth Stewart's "Make It Opaque"