Appendix

Digital Guitar Tuner

Eric Tai | Daniel Tsui

ECE 476: Spring 2005

Appendix

Appendix A: Commented program listing

//time base will be 10e-4

//stuff that needs to be added in:

//PORT hookups:

//Port A: ADC

//Port B: LED outputs

//Port D: pushbutton inputs

#asm

.equ __lcd_port=0x15

#endasm

#include <lcd.h> // LCD driver routines

#include <Mega32.h>

#include <stdio.h>

#define begin {

#define end }

//signal timer state machine

#define start 1

#define counting 2

//pushbutton state machine

#define release 1

#define debounce 2

#define detect_t 3

#define done 4

#define still_p 5

#define debounce_r 6

//guitar frequencies

#define E2 12134 // period in us. E2 period is 12134x10^-6

#define A2 9090

#define D3 6180

#define G3 5102

#define B3 4049

#define E4 3033

#define STIME 2

#define BUTTONTIME 500 //ever 50ms

#define mult(a,b) ((char)((((long)(a))*((long)(((int)b)<<8)))>>16)) //multiply 8-bit integer by 8-bit fraction

//declaring functions

char lcd_buffer[17];

void initialize(void);

void pollbuttons(void);

void dosignal(void);

void eval_timer(void);

//variables

unsigned char x, lastx, y, lasty; //raw A to D number

float a,b;

char state, buttonstate, count; //timing state machine

unsigned int timer, endtime; //unsigned int from 0 to 65535

char threshold, thres;

//counters

char signal_time;

char led;

char buttons, maybe; //store states for pushbutton

int stringval; //the string being hit

int time1; //timer1

unsigned int temp;

unsigned int lower2, upper2, lower1, upper1, lower0, upper0, cal;

//*****************************************************

//timer 0 compare ISR

interrupt [TIM0_COMP] void timer0_compare(void)

begin

if (time1 > 0) --time1;

if (signal_time > 0) --signal_time;

timer++;

end

//*******************************************************

void initialize(void)

begin

lcd_init(16);

//init the A to D converter

TIMSK = 2;

OCR0 = 25; //count up to 25

TCCR0=0b000001011; //prescale by 64

ADMUX = 0b01100000; //enable ADC and set prescaler to 1/128*16MHz=125,000

//user internal vref

//and clear interupt enable

//and start a conversion

ADCSR = 0b11000111;

//initialize buttons

DDRB = 0xff; //output LED's

PORTB = 0x00; //start all off

DDRD = 0x00; //input pushbuttons

PORTD = 0xff;

//initialize variables

time1 = BUTTONTIME;

signal_time = STIME;

threshold = 127; //digitized value for zero ----CHANGE THIS VALUE

thres = 0; // the amount of leeway on tuning

led = 0x00;

PORTB = ~led;

state = start;

b=0.0305;

a=0.9391;

buttonstate = release;

upper0 = 0;

upper1 = 0;

upper2 = 0;

lower0 = 0;

lower1 = 0;

lower2 = 0;

#asm

sei

#endasm

temp = 0;

count=0;

end

void pollbuttons(void)

//function: to set the correct string that is being checked. Can occur every 30 ms. We will have to debounce.

begin

time1 = BUTTONTIME;

buttons = PIND;

//debounce

switch (buttonstate)

begin

case release:

//PORTB = 0b11111111;

//pushbuttons not pressed

if (buttons != 0xff) //if something pressed

begin

maybe = buttons; //keep old buttonpressed number

buttonstate = debounce; //change states

end

break;

case debounce:

//is pushbuttons pressed?

if (buttons == maybe) buttonstate = still_p; //button pressed

else buttonstate = release;//button not pressed

break;

case still_p:

//press confirmed

if (buttons == maybe) //button IS pressed

begin

switch (buttons) //button capture

begin

case 0b11111110:

stringval = E2;

PORTB = 0b11111110;

lcd_clear();

lcd_gotoxy(0,0);

sprintf(lcd_buffer,"String E2");

lcd_puts(lcd_buffer);

b=0.0450;

a=0.9099;

//passing frequency bounds

upper2 = 2527;

upper1 = 2498;

upper0 = 2470;

lower0 = 2386;

lower1 = 2358;

lower2 = 2331;

cal=20;

threshold = 127;

break;

case 0b11111101:

stringval = A2;

lcd_clear();

lcd_gotoxy(0,0);

lcd_putsf("String A2");

b=0.0592;

a=0.8816;

//passing frequency bounds

upper2 = 1893;

upper1 = 1871;

upper0 = 1850;

lower0 = 1786;

lower1 = 1766;

lower2 = 1476;

cal=30;

threshold = 127;

break;

case 0b11111011:

stringval = D3;

lcd_clear();

lcd_gotoxy(0,0);

lcd_putsf("String D3");

b=0.0797;

a=0.8406;

//passing frequency bounds

upper2 = 1419;

upper1 = 1402;

upper0 = 1386;

lower0 = 1339;

lower1 = 1324;

lower2 = 1308;

cal=30;

threshold = 127;

break;

case 0b11110111:

stringval = G3;

lcd_clear();

lcd_gotoxy(0,0);

lcd_putsf("String G3");

b=0.0730;

a=0.8541;

//passing frequency bounds

upper2 = 1062;

upper1 = 1050;

upper0 = 1038;

lower0 = 1003;

lower1 = 991;

lower2 = 980;

cal=10;

threshold = 80;

break;

case 0b11101111:

stringval = B3;

lcd_clear();

lcd_gotoxy(0,0);

lcd_putsf("String B3");

b=0.1270;

a=0.7459;

//passing frequency bounds

upper2 = 843;

upper1 = 834;

upper0 = 824;

lower0 = 796;

lower1 = 787;

lower2 = 778;

cal=10;

threshold = 127;

break;

case 0b11011111:

stringval = E4;

lcd_clear();

lcd_gotoxy(0,0);

lcd_putsf("String E4");

b=0.1648;

a=0.6705;

//passing frequency bounds

upper2 = 632;

upper1 = 624;

upper0 = 617;

lower0 = 596;

lower1 = 589;

lower2 = 583;

cal=10;

threshold = 127;

break;

default: break;

end

else buttonstate = debounce_r;

break;

case debounce_r:

if (buttons == maybe) buttonstate = still_p;

else buttonstate = release;

break;

end //switch */

end //pollbuttons

void dosignal(void)

//to filter then time the input frequency. Needs to be occurring every 1 microsecond.

begin

signal_time = STIME;

lastx=x;

lasty=y;

x=ADCH; //get signal

ADCSR.6=1; //get next sample

endtime=timer; //get current timer value for the period

//digital filter

y=((char)(b*x+b*lastx+a*lasty));

if(lasty<threshold && y > threshold) //cross zero from negative to positive

begin

count++;

if(count==20)

begin

eval_timer(); //check if timer value is in bounds

count=0;

timer=0; //reset timer and begin measurement for next 20 periods

end

void eval_timer(void)

begin

endtime = endtime + cal;

lcd_clear();

lcd_gotoxy(0,0);

sprintf(lcd_buffer,"targ: %d-%d",lower0,upper0);

lcd_puts(lcd_buffer);

lcd_gotoxy(0,1);

sprintf(lcd_buffer,"%d",endtime);

lcd_puts(lcd_buffer);

if (endtime > lower0 && endtime < upper0) PORTB = 0b11110111; //light up middle LED

else if (endtime > upper0 && endtime < upper1) PORTB = 0b11111011; //light up +30 cent

else if (endtime > upper1 && endtime < upper2) PORTB = 0b11111101; //light up +50 cent

else if (endtime > upper2) PORTB = 0b11111110; //light up +70cent

else if (endtime > lower1 && endtime < lower0) PORTB = 0b11101111; //light up -30 cent

else if (endtime > lower2 && endtime < lower1) PORTB = 0b11011111; //-50

else if (endtime < lower2) PORTB = 0b10111111; //-70

end

void main(void)

begin

initialize();

// measure and display loop

while (1)

begin

if(signal_time==0) dosignal(); //get and process signal

if(time1==0) pollbuttons(); //get input from buttons

end

Appendix B: Schematics

Figure: Flow Diagram

Picture: Completed Circuit

Appendix C: Cost details with all part numbers and their price.

This cost will include components supplied by the lab, including MCU and power supplies but excluding the STK500.

Item	Cost
1 x breadboard	6.00
1 x Power Supply	5.00
1 x Mega32	8.00
1 x LCD Display (16x2)	8.00
1 x Custom PC Board	5.00
11 x Resistors	0.11
2 x Capacitors	0.50
2 x 1N914 Diodes	0.02
1 x LMC7111 Op Amp	1.55
1 x Audio Jack	2.00
2 x Solder-linked breadboards	5.00
TOTAL:	41.18

Appendix D: Specific Tasks

Programming Code – ejt22, ddt7.

Analog Op Amp – ddt7, etj22.

Digital Filter – ddt7

Web Site – ejt22.

Pushbuttons and LCD – ejt22, ddt7

Appendix E: References

Data sheets

LCD Display

LMC7111 Op Amp

MEGA32

Vendor sites

Radio Shack. www.radioshack.com

Background sites/papers

Reeves, Galen and Dimitry Berenson. “Digital Guitar Tuner”. Spring 2004. http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2004/ddb25/index.htm

Wolfe, Joe. “Note Names, MIDI Numbers and Frequencies.” http://www.phys.unsw.edu.au/~jw/notes.html