OpenAudio_ArduinoLibrary/synth_sine_f32.cpp

/*
 * AudioSynthWaveformSine_F32
 *
 * Created: Chip Audette (OpenAudio) Feb 2017
 * Modeled on: AudioSynthWaveformSine from Teensy Audio Library
 *
 * Purpose: Create sine wave of given amplitude and frequency
 *
 * License: MIT License. Use at your own risk.
 *
 */

#include "synth_sine_f32.h"
#include "utility/dspinst.h"

// data_waveforms.c
extern "C" {
  extern const int16_t AudioWaveformSine[257];
}

void AudioSynthWaveformSine_F32::update(void)  {
    audio_block_f32_t *block;
    uint32_t i, ph, inc, index, scale;
    int32_t val1, val2;
    static uint32_t block_length = 0;

    if (enabled) {
        if (magnitude) {
            block = allocate_f32();
            if (block) {
                block_length = (uint32_t)block->length;
                ph = phase_accumulator;
                inc = phase_increment;
                for (i=0; i < block_length; i++) {
                    index = ph >> 24;
                    val1 = AudioWaveformSine[index];
                    val2 = AudioWaveformSine[index+1];
                    scale = (ph >> 8) & 0xFFFF;
                    val2 *= scale;
                    val1 *= 0x10000 - scale;
#if (defined(KINETISK) || defined(__IMXRT1062__) )
                    block->data[i] = (float) multiply_32x32_rshift32(val1 + val2, magnitude);
#elif defined(KINETISL)
                    block->data[i] = (float) ((((val1 + val2) >> 16) * magnitude) >> 16);
#endif
                    ph += inc;
                    block->data[i] = block->data[i] / 32767.0f; // scale to float
                }
                phase_accumulator = ph;

                AudioStream_F32::transmit(block);
                AudioStream_F32::release(block);
                return;
            }
        }// end if (magnitude)
        phase_accumulator += phase_increment * block_length;   // continue sine wave while magnitude==0
    }  // end if (enabled)
}