forked from PaulStoffregen/Audio
/
synth_dc.h
142 lines (136 loc) · 4.4 KB
/
synth_dc.h
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/* Audio Library for Teensy 3.X
* Copyright (c) 2014, Paul Stoffregen, paul@pjrc.com
*
* Development of this audio library was funded by PJRC.COM, LLC by sales of
* Teensy and Audio Adaptor boards. Please support PJRC's efforts to develop
* open source software by purchasing Teensy or other PJRC products.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice, development funding notice, and this permission
* notice shall be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#ifndef synth_dc_h_
#define synth_dc_h_
#include "Arduino.h"
#include "AudioStream.h"
#include "utility/dspinst.h"
// compute (a - b) / c
// handling 32 bit interger overflow at every step
// without resorting to slow 64 bit math
#if defined(KINETISK) || defined(__SAMD51__)
static inline int32_t substract_int32_then_divide_int32(int32_t a, int32_t b, int32_t c) __attribute__((always_inline, unused));
static inline int32_t substract_int32_then_divide_int32(int32_t a, int32_t b, int32_t c)
{
int r;
r = substract_32_saturate(a,b);
if ( !get_q_psr() ) return (r/c);
clr_q_psr();
if ( c==0 ) r=0;
if (__builtin_abs(c)<=1) return r;
return (a/c)-(b/c);
}
#else
// compute (a - b) / c ... handling 32 bit interger overflow without slow 64 bit math
static inline int32_t substract_int32_then_divide_int32(int32_t a, int32_t b, int32_t c) __attribute__((always_inline, unused));
static inline int32_t substract_int32_then_divide_int32(int32_t a, int32_t b, int32_t c)
{
uint32_t diff;
uint8_t negative;
if (a >= 0) {
if (b >= 0) {
return (a - b) / c; // no overflow if both a & b are positive
} else {
diff = a + (b * -1); // assumes 0x80000000 * -1 == 0x80000000
negative = 0;
}
} else {
if (b >= 0) {
diff = (a * -1) + b; // assumes 0x80000000 * -1 == 0x80000000
negative = 1;
} else {
return (a - b) / c; // no overflow if both a & b are negative
}
}
if (c >= 0) {
diff = diff / (uint32_t)c;
} else {
diff = diff / (uint32_t)(c * -1);
negative ^= 1;
}
if (negative) {
if (diff > 0x7FFFFFFF) return 0x80000000;
return (int32_t)diff * -1;
} else {
if (diff > 0x7FFFFFFF) return 0x7FFFFFFF;
return (int32_t)diff;
}
}
#endif
class AudioSynthWaveformDc : public AudioStream
{
public:
AudioSynthWaveformDc() : AudioStream(0, NULL), state(0), magnitude(0) {}
// immediately jump to the new DC level
void amplitude(float n) {
if (n > 1.0) n = 1.0;
else if (n < -1.0) n = -1.0;
int32_t m = (int32_t)(n * 2147418112.0);
__disable_irq();
magnitude = m;
state = 0;
__enable_irq();
}
// slowly transition to the new DC level
void amplitude(float n, float milliseconds) {
if (milliseconds <= 0.0) {
amplitude(n);
return;
}
if (n > 1.0) n = 1.0;
else if (n < -1.0) n = -1.0;
int32_t c = (int32_t)(milliseconds*(AUDIO_SAMPLE_RATE_EXACT/1000.0));
if (c == 0) {
amplitude(n);
return;
}
int32_t t = (int32_t)(n * 2147418112.0);
__disable_irq();
target = t;
if (target == magnitude) {
state = 0;
__enable_irq();
return;
}
increment = substract_int32_then_divide_int32(target, magnitude, c);
if (increment == 0) {
increment = (target > magnitude) ? 1 : -1;
}
state = 1;
__enable_irq();
}
float read(void) {
int32_t m = magnitude;
return (float)m * (1.0 / 2147418112.0);
}
virtual void update(void);
private:
uint8_t state; // 0=steady output, 1=transitioning
int32_t magnitude; // current output
int32_t target; // designed output (while transitiong)
int32_t increment; // adjustment per sample (while transitiong)
};
#endif