Merge branch 'master' of ssh://git.xpub.nl:2501/XPUB/special-issue-x

master
Max Lehmann 5 years ago
commit 91feaf16d7

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STRINGS1
======
* Knob 1: Loop start
* Knob 2: Loop length
* Knob 3: Pitch
* Input 3: Gate trigger
All code ripped from Framen who ripped and modified these fine people's work:
* http://www.ginkosynthese.com/product/grains/
* http://playground.arduino.cc/Code/PCMAudio
* michael@hurts.ca
* https://www.facebook.com/HRTLmuzik
* https://github.com/thatpixguy/hrtl-amen

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#include <stdint.h>
#include <avr/interrupt.h>
#include <avr/io.h>
#include <avr/pgmspace.h>
#include "sample.h"
#define LED_PIN 13
#define SPEAKER_PIN 11
#define KNOB_1 (0)
#define KNOB_2 (1)
#define KNOB_3 (2)
#define INPUT_3 (3)
volatile uint16_t sample;
volatile uint16_t loop_start;
volatile uint16_t loop_length;
volatile uint16_t index_bounds;
volatile uint16_t loop_overflow;
volatile boolean gate;
volatile boolean gate_prev;
byte lastSample;
void startPlayback()
{
pinMode(SPEAKER_PIN, OUTPUT);
// Set up Timer 2 to do pulse width modulation on the speaker pin.
// Use internal clock (datasheet p.160)
ASSR &= ~(_BV(EXCLK) | _BV(AS2));
// Set fast PWM mode (p.157)
TCCR2A |= _BV(WGM21) | _BV(WGM20);
TCCR2B &= ~_BV(WGM22);
// Do non-inverting PWM on pin OC2A (p.155)
// On the Arduino this is pin 11.
TCCR2A = (TCCR2A | _BV(COM2A1)) & ~_BV(COM2A0);
TCCR2A &= ~(_BV(COM2B1) | _BV(COM2B0));
// No prescaler (p.158)
TCCR2B = (TCCR2B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);
// Set initial pulse width to the first sample.
OCR2A = pgm_read_byte(&sound_data[0]);
// Set up Timer 1 to send a sample every interrupt.
cli();
// Set CTC mode (Clear Timer on Compare Match) (p.133)
// Have to set OCR1A *after*, otherwise it gets reset to 0!
TCCR1B = (TCCR1B & ~_BV(WGM13)) | _BV(WGM12);
TCCR1A = TCCR1A & ~(_BV(WGM11) | _BV(WGM10));
// No prescaler (p.134)
TCCR1B = (TCCR1B & ~(_BV(CS12) | _BV(CS11))) | _BV(CS10);
// Set the compare register (OCR1A).
// OCR1A is a 16-bit register, so we have to do this with
// interrupts disabled to be safe.
OCR1A = F_CPU / SAMPLE_RATE; // 16e6 / 8000 = 2000
// Enable interrupt when TCNT1 == OCR1A (p.136)
TIMSK1 |= _BV(OCIE1A);
lastSample = pgm_read_byte(&sound_data[sound_length - 1]);
sample = 0;
sei();
}
void stopPlayback()
{
TIMSK1 &= ~_BV(OCIE1A); // Disable playback per-sample interrupt.
TCCR1B &= ~_BV(CS10); // Disable the per-sample timer completely.
TCCR2B &= ~_BV(CS10); // Disable the PWM timer.
digitalWrite(SPEAKER_PIN, LOW);
}
void setup()
{
pinMode(LED_PIN, OUTPUT);
digitalWrite(LED_PIN, HIGH);
startPlayback();
loop_start = 0;
loop_length = sound_length;
gate = false;
gate_prev = false;
}
// This is called at 8000 Hz to load the next sample.
ISR(TIMER1_COMPA_vect)
{
if(sample >= index_bounds)
{
sample = loop_start;
}
else if((sample < loop_start) &&
(sample >= loop_overflow))
{
sample = loop_start;
}
else if((gate == true) &&
(gate_prev == false))
{
sample = loop_start;
}
else
{
OCR2A = pgm_read_byte(&sound_data[sample % sound_length]);
}
gate_prev = gate;
sample++;
}
void loop()
{
loop_start = analogRead(KNOB_1) / 1024.0 * sound_length;
loop_length = (analogRead(KNOB_2) + 1) / 1024.0 * sound_length;
OCR1A = (512.0 / (analogRead(KNOB_3) + 1)) * (F_CPU / SAMPLE_RATE);
gate = analogRead(3) >> 9; // 10 bits in. gate < 512 == off, gate >= 512 == on
// can be up to 2x sound length. the more you know.
index_bounds = loop_start + loop_length;
// this will set the overflow length. take the loop overflow into account when checking the loop boundaries
if(index_bounds > sound_length)
{
loop_overflow = index_bounds - sound_length;
}
else
{
loop_overflow = 0;
}
}

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