143 lines
4.4 KiB
C++
143 lines
4.4 KiB
C++
/* Audio Library for Teensy 3.X
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* Copyright (c) 2014, Paul Stoffregen, paul@pjrc.com
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*
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* Development of this audio library was funded by PJRC.COM, LLC by sales of
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* Teensy and Audio Adaptor boards. Please support PJRC's efforts to develop
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* open source software by purchasing Teensy or other PJRC products.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice, development funding notice, and this permission
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* notice shall be included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef synth_dc_h_
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#define synth_dc_h_
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#include "Arduino.h"
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#include "AudioStream.h"
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#include "utility/dspinst.h"
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// compute (a - b) / c
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// handling 32 bit interger overflow at every step
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// without resorting to slow 64 bit math
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#if defined(__ARM_ARCH_7EM__)
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static inline int32_t substract_int32_then_divide_int32(int32_t a, int32_t b, int32_t c) __attribute__((always_inline, unused));
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static inline int32_t substract_int32_then_divide_int32(int32_t a, int32_t b, int32_t c)
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{
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int r;
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r = substract_32_saturate(a,b);
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if ( !get_q_psr() ) return (r/c);
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clr_q_psr();
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if ( c==0 ) r=0;
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if (__builtin_abs(c)<=1) return r;
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return (a/c)-(b/c);
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}
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#else
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// compute (a - b) / c ... handling 32 bit interger overflow without slow 64 bit math
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static inline int32_t substract_int32_then_divide_int32(int32_t a, int32_t b, int32_t c) __attribute__((always_inline, unused));
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static inline int32_t substract_int32_then_divide_int32(int32_t a, int32_t b, int32_t c)
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{
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uint32_t diff;
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uint8_t negative;
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if (a >= 0) {
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if (b >= 0) {
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return (a - b) / c; // no overflow if both a & b are positive
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} else {
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diff = a + (b * -1); // assumes 0x80000000 * -1 == 0x80000000
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negative = 0;
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}
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} else {
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if (b >= 0) {
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diff = (a * -1) + b; // assumes 0x80000000 * -1 == 0x80000000
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negative = 1;
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} else {
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return (a - b) / c; // no overflow if both a & b are negative
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}
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}
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if (c >= 0) {
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diff = diff / (uint32_t)c;
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} else {
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diff = diff / (uint32_t)(c * -1);
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negative ^= 1;
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}
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if (negative) {
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if (diff > 0x7FFFFFFF) return 0x80000000;
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return (int32_t)diff * -1;
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} else {
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if (diff > 0x7FFFFFFF) return 0x7FFFFFFF;
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return (int32_t)diff;
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}
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}
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#endif
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class AudioSynthWaveformDc : public AudioStream
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{
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public:
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AudioSynthWaveformDc() : AudioStream(0, NULL), state(0), magnitude(0) {}
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// immediately jump to the new DC level
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void amplitude(float n) {
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if (n > 1.0) n = 1.0;
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else if (n < -1.0) n = -1.0;
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int32_t m = (int32_t)(n * 2147418112.0);
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__disable_irq();
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magnitude = m;
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state = 0;
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__enable_irq();
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}
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// slowly transition to the new DC level
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void amplitude(float n, float milliseconds) {
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if (milliseconds <= 0.0) {
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amplitude(n);
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return;
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}
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if (n > 1.0) n = 1.0;
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else if (n < -1.0) n = -1.0;
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int32_t c = (int32_t)(milliseconds*(AUDIO_SAMPLE_RATE_EXACT/1000.0));
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if (c == 0) {
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amplitude(n);
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return;
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}
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int32_t t = (int32_t)(n * 2147418112.0);
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__disable_irq();
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target = t;
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if (target == magnitude) {
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state = 0;
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__enable_irq();
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return;
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}
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increment = substract_int32_then_divide_int32(target, magnitude, c);
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if (increment == 0) {
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increment = (target > magnitude) ? 1 : -1;
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}
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state = 1;
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__enable_irq();
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}
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float read(void) {
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int32_t m = magnitude;
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return (float)m * (1.0 / 2147418112.0);
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}
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virtual void update(void);
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private:
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uint8_t state; // 0=steady output, 1=transitioning
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int32_t magnitude; // current output
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int32_t target; // designed output (while transitiong)
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int32_t increment; // adjustment per sample (while transitiong)
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};
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#endif
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