Hi folks,
I'm struggling with getting this code to be a bit more efficient. Basically right now it detects the frequency from a guitar and then converts the frequency detected into its relative MIDI note, I've got it set to only detect and play MIDI notes from 40-69. It works and it can play the correct note that is played from the guitar but the main problem I have now is that it also plays other notes around it, I'm not too sure of the cause of it now but my guess is that it's from the initial hit from the string or feedback produced. Only solutions I can think of are to reduce the rate it can pick up notes and maybe adding a short delay before it sends out the frequency to MIDI to try and get rid of any inconsistencies when hitting the string.
Any help would be appreciated greatly thanks.
Here's the code I have so far:
#define DEBUG_MODE 0 // 1 = text output to Serial Monitor, 0 = binary to Hairless MIDI
//clipping indicator variables
boolean clipping = 0;
//data storage variables
byte newData = 0;
byte prevData = 0;
unsigned int time = 0; //keeps time and sends vales to store in timer[] occasionally
int timer[10]; //sstorage for timing of events
int slope[10]; //storage fro slope of events
unsigned int totalTimer; //used to calculate period
unsigned int period; //storage for period of wave
byte index = 0; //current storage index
float frequency; //storage for frequency calculations
int maxSlope = 0; //used to calculate max slope as trigger point
int newSlope; //storage for incoming slope data
//variables for decided whether you have a match
byte noMatch = 0; //counts how many non-matches you've received to reset variables if it's been too long
byte slopeTol = 3; //slope tolerance- adjust this if you need
int timerTol = 10; //timer tolerance- adjust this if you need
//for MIDI instructions
constexpr int noteON = 144; //144 = 10010000 in binary, note on command
constexpr int noteOFF = 128; //128 = 10000000 in binary, note off command
int velocity = 100;
//Full spectrum of notes
const float MIDI_FREQUENCY[]{
// C C-sharp D D-sharp E F F-sharp G G-sharp A A-sharp B
8.18, 8.66, 9.18, 9.73, 10.30, 10.92, 11.56, 12.25, 12.98, 13.75, 14.57, 15.44, // Octave -1
16.35, 17.32, 18.35, 19.45, 20.60, 21.83, 23.12, 24.50, 25.96, 27.50, 29.14, 30.87, // Octave 0
32.70, 34.65, 36.71, 38.89, 41.20, 43.65, 46.25, 49.00, 51.91, 55.00, 58.27, 61.74, // Octave 1
65.41, 69.30, 73.42, 77.78, 82.41, 87.31, 92.50, 98.00, 103.83, 110.00, 116.54, 123.47, // Octave 2
130.81, 138.59, 146.83, 155.56, 164.81, 174.61, 185.00, 196.00, 207.65, 220.00, 233.08, 246.94, // Octave 3
261.63, 277.18, 293.66, 311.13, 329.63, 349.23, 369.99, 392.00, 415.30, 440.00, 466.16, 493.88, // Octave 4
523.25, 554.37, 587.33, 622.25, 659.25, 698.46, 739.99, 783.99, 830.61, 880.00, 932.33, 987.77, // Octave 5
1046.50, 1108.73, 1174.66, 1244.51, 1318.51, 1396.91, 1479.98, 1567.98, 1661.22, 1760.00, 1864.66, 1975.53, // Octave 6
2093.00, 2217.46, 2349.32, 2489.02, 2637.02, 2793.83, 2959.96, 3135.96, 3322.44, 3520.00, 3729.31, 3951.07, // Octave 7
4186.01, 4434.92, 4698.63, 4978.03, 5274.04, 5587.65, 5919.91, 6271.93, 6644.88, 7040.00, 7458.62, 7902.13, // Octave 8
8372.02, 8869.84, 9397.26, 9956.06, 10548.08, 11175.30, 11839.82, 12543.86 // Octave 9 (partial)
};
//Test Spectrum of Notes
/*
const float MIDI_FREQUENCY[]{
// E F F-sharp G G-sharp A A-sharp B C C-sharp D D-sharp
8.18, 8.66, 9.18, 9.73, 10.30, 10.92, 11.56, 12.25, 12.98, 13.75, 14.57, 15.44, // Octave -1
16.35, 17.32, 18.35, 19.45, 20.60, 21.83, 23.12, 24.50, 25.96, 27.50, 29.14, 30.87, // Octave 0
32.70, 34.65, 36.71, 38.89, 41.20, 43.65, 46.25, 49.00, 51.91, 55.00, 58.27, 61.74, // Octave 1
65.41, 69.30, 73.42, 77.78, 82.41, 87.31, 92.50, 98.00, 103.83, 110.00, 116.54, 123.47, // Octave 2
130.81, 138.59, 146.83, 155.56, 164.81, 174.61, 185.00, 196.00, 207.65, 220.00, 233.08, 246.94, // Octave 3
261.63, 277.18, 293.66, 311.13, 329.63, 349.23, 369.99, 392.00, 415.30, 440.00, 466.16, 493.88, // Octave 4
523.25, 554.37, 587.33, 622.25, 659.25, 698.46, 739.99, 783.99, 830.61, 880.00, 932.33, 987.77, // Octave 5
1046.50, 1108.73, 1174.66, 1244.51, 1318.51, 1396.91, 1479.98, 1567.98, 1661.22, 1760.00, 1864.66, 1975.53, // Octave 6
2093.00, 2217.46, 2349.32, 2489.02, 2637.02, 2793.83, 2959.96, 3135.96, 3322.44, 3520.00, 3729.31, 3951.07, // Octave 7
4186.01, 4434.92, 4698.63, 4978.03, 5274.04, 5587.65, 5919.91, 6271.93, 6644.88, 7040.00, 7458.62, 7902.13, // Octave 8
8372.02, 8869.84, 9397.26, 9956.06, 10548.08, 11175.30, 11839.82, 12543.86 // Octave 9 (partial)
};
*/
const uint8_t MIDI_NOTE_C0 = 40;
const uint8_t MIDI_NOTE_C9 = 69;
static byte LastNote = 0;
void setup()
{
Serial.begin(9600);
pinMode(13, OUTPUT); //led indicator pin
pinMode(12, OUTPUT); //output pin
cli(); //diable interrupts
//set up continuous sampling of analog pin 0 at 38.5kHz
//clear ADCSRA and ADCSRB registers
ADCSRA = 0;
ADCSRB = 0;
ADMUX |= (1 << REFS0); //set reference voltage
ADMUX |= (1 << ADLAR); //left align the ADC value- so we can read highest 8 bits from ADCH register only
ADCSRA |= (1 << ADPS2) | (1 << ADPS0); //set ADC clock with 32 prescaler- 16mHz/32=500kHz
ADCSRA |= (1 << ADATE); //enabble auto trigger
ADCSRA |= (1 << ADIE); //enable interrupts when measurement complete
ADCSRA |= (1 << ADEN); //enable ADC
ADCSRA |= (1 << ADSC); //start ADC measurements
sei(); //enable interrupts
}
ISR(ADC_vect)
{ //when new ADC value ready
PORTB &= B11101111; //set pin 12 low
prevData = newData; //store previous value
newData = ADCH; //get value from A0
if (prevData < 127 && newData >= 127)
{ //if increasing and crossing midpoint
newSlope = newData - prevData; //calculate slope
if (abs(newSlope - maxSlope) < slopeTol)
{ //if slopes are ==
//record new data and reset time
slope[index] = newSlope;
timer[index] = time;
time = 0;
if (index == 0)
{ //new max slope just reset
PORTB |= B00010000; //set pin 12 high
noMatch = 0;
index++; //increment index
}
else if (abs(timer[0] - timer[index]) < timerTol && abs(slope[0] - newSlope) < slopeTol)
{ //if timer duration and slopes match
//sum timer values
totalTimer = 0;
for (byte i = 0; i < index; i++)
{
totalTimer += timer[i];
}
period = totalTimer; //set period
//reset new zero index values to compare with
timer[0] = timer[index];
slope[0] = slope[index];
index = 1; //set index to 1
PORTB |= B00010000; //set pin 12 high
noMatch = 0;
}
else
{ //crossing midpoint but not match
index++; //increment index
if (index > 9)
{
reset();
}
}
}
else if (newSlope > maxSlope)
{ //if new slope is much larger than max slope
maxSlope = newSlope;
time = 0; //reset clock
noMatch = 0;
index = 0; //reset index
}
else
{ //slope not steep enough
noMatch++; //increment no match counter
if (noMatch > 9)
{
reset();
}
}
}
if (newData == 0x00 || newData == 0xFF)
{ //if clipping
PORTB |= B00100000; //set pin 13 high- turn on clipping indicator led
clipping = 1; //currently clipping
}
time++; //increment timer at rate of 38.5kHz
}
void reset()
{ //clea out some variables
index = 0; //reset index
noMatch = 0; //reset match couner
maxSlope = 0; //reset slope
}
void checkClipping()
{ //manage clipping indicator LED
if (clipping)
{ //if currently clipping
PORTB &= B11011111; //turn off clipping indicator led
clipping = 0;
}
}
void loop()
{
checkClipping();
frequency = 38462 / float(period); //calculate frequency timer rate/period
/*
#if DEBUG_MODE
//print results
Serial.print(frequency);
Serial.println(" hz");
#endif
*/
//MIDI notes
for (byte note = MIDI_NOTE_C0; note < MIDI_NOTE_C9; note++)
{
if (frequency < (MIDI_FREQUENCY[note] + MIDI_FREQUENCY[note + 1]) / 2)
{
// Matching note!
if (note != LastNote)
{
// The note has changed so turn off the previous note
MIDImessage(noteOFF, LastNote, velocity);
MIDImessage(noteON, note, velocity);
}
LastNote = note;
break; // No need to look for more matches.
}
}
}
//send MIDI message
void MIDImessage(byte command, byte MIDInote, byte MIDIvelocity)
{
Serial.write(command); //send note on or note off command
Serial.write(MIDInote); //send pitch data
Serial.write(MIDIvelocity); //send velocity data
/*
Serial.print(command); //send note on or note off command
Serial.print(MIDInote); //send pitch data
Serial.print(MIDIvelocity); //send velocity data
Serial.println(" ");
*/
}
/*
//send MIDI message
void MIDImessage(byte command, byte MIDInote, byte MIDIvelocity)
{
#if DEBUG_MODE
// Display each MIDI message as text for debugging
switch (command)
{
case noteON: Serial.print(noteON); break;
case noteOFF: Serial.print(noteOFF); break;
default:
Serial.print(command); // show note on or note off command
break;
}
//Serial.print(", ");
Serial.print(MIDInote); // show pitch data
//Serial.print(", ");
Serial.print(MIDIvelocity); // send velocity data
#else
// Send each MIDI message to Hairless MIDI as three binary bytes
Serial.write(command); //send note on or note off command
Serial.write(MIDInote); //send pitch data
Serial.write(MIDIvelocity); //send velocity data
Serial.print(command); //send note on or note off command
Serial.print(MIDInote); //send pitch data
Serial.print(MIDIvelocity); //send velocity data
Serial.println(" ");
#endif
}
*/
/*
//send MIDI message
void MIDImessage(byte command, byte MIDInote, byte MIDIvelocity)
{
#if DEBUG_MODE
// Display each MIDI message as text for debugging
switch (command)
{
case noteON: Serial.print("noteON"); break;
case noteOFF: Serial.print("noteOFF"); break;
default:
Serial.print(command); // show note on or note off command
break;
}
Serial.print(", ");
Serial.print(MIDInote); // show pitch data
Serial.print(", ");
Serial.println(MIDIvelocity); // send velocity data
#else
// Send each MIDI message to Hairless MIDI as three binary bytes
Serial.write(command); //send note on or note off command
Serial.write(MIDInote); //send pitch data
Serial.write(MIDIvelocity); //send velocity data
Serial.print(command); //send note on or note off command
Serial.print(MIDInote); //send pitch data
Serial.print(MIDIvelocity); //send velocity data
#endif
}
*/