text: /*
   * Generic GPIO led
   *
   * Copyright (C) 2019 - 2020 Andy Green <andy@warmcat.com>
   *
   * 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 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.
   */
  #include "private-lib-core.h"
  
  static const lws_led_intensity_t sineq16[] = {
  
  	/*
  	 * Quadrant at sin(270) in 16 samples, normalized so
  	 * -1 == 0 and 0 == 32767
  	 */
  
  	    0,   158,   630,  1411,  2494,  3869,  5522,  7437,
  	 9597, 11980, 14562, 17321, 20228, 23225, 26374, 29555,
  	32767 /* to interpolate against */
  };
  
  /*
   * Elaborate the 90 degree phase table to 360 degrees and offset to +32768,
   * notice for the last sample we have to interpolate against a 17th sample
   * reflecting full scale to avoid clipping due to interpolation against the
   * 16th sample again
   */
  
  static lws_led_intensity_t
  sine_lu(int n, int next)
  {
          switch ((n >> 4) & 3) {
          case 1:
          	/* forwards */
                  return 32768 + sineq16[(n & 15) + next];
          case 2:
          	/* scan it backwards */
                  return 32768 + sineq16[15 - (n & 15) + (!next)];
          case 3:
          	/* forwards */
                  return 32768 - sineq16[(n & 15) + next];
          default:
          	/* scan it backwards */
                  return 32768 - sineq16[15 - (n & 15) + (!next)];
          }
  }
  
  /*
   * The normalized phase resolution is 16-bit, however much table you decide to
   * have needs interpolating or indexing in a reduced number of significant
   * phase bits if it doesn't have the same phase resolution.
   *
   * In this sine table we have a 16 x 15-bit sample quadrant reflected 4 times
   * to make 360 degrees, so 64 accurate sample points, with the rest of the
   * intermediate phases generated by linear interpolation.  That probably would
   * sound a bit funky, but for modulating light dynamically it's more than
   * enough.
   */
  
  lws_led_intensity_t
  lws_led_func_sine(lws_led_seq_phase_t n)
  {
          /*
           * 2: quadrant
           * 4: table entry in quadrant
           * 10: interp (LSB)
           */
  
          return (sine_lu(n >> 10, 0) * (0x3ff - (n & 0x3ff)) +
          	sine_lu(n >> 10, 1) * (n & 0x3ff)) / 0x3ff;
  }
  
  lws_led_intensity_t
  lws_led_func_linear(lws_led_seq_phase_t n)
  {
  	return (lws_led_intensity_t)n;
  }
  
  
  static lws_led_intensity_t
  lws_led_func_static(lws_led_seq_phase_t n)
  {
  	return ((int)n * LWS_LED_MAX_INTENSITY) / 2;
  }
  
  const lws_led_sequence_def_t lws_pwmseq_static_off = {
  	.func			= lws_led_func_static,
  	.ledphase_offset	= 0,
  	.ledphase_total		= 0,
  	.ms			= 0
  };
  
  const lws_led_sequence_def_t lws_pwmseq_static_half = {
  	.func			= lws_led_func_static,
  	.ledphase_offset	= 1,
  	.ledphase_total		= 0,
  	.ms			= 0
  };
  
  const lws_led_sequence_def_t lws_pwmseq_static_on = {
  	.func			= lws_led_func_static,
  	.ledphase_offset	= 2,
  	.ledphase_total		= 0,
  	.ms			= 0
  };
  
  const lws_led_sequence_def_t lws_pwmseq_sine_up = {
  	.func			= lws_led_func_sine,
  	.ledphase_offset	= 0, /* already at 0 amp at 0 phase */
  	.ledphase_total		= LWS_LED_FUNC_PHASE / 2, /* 180 degree ./^ */
  	.ms			= 300
  };
  
  const lws_led_sequence_def_t lws_pwmseq_sine_down = {
  	.func			= lws_led_func_sine,
  	.ledphase_offset	= LWS_LED_FUNC_PHASE / 2, /* start at peak */
  	.ledphase_total		= LWS_LED_FUNC_PHASE / 2, /* 180 degree ./^ */
  	.ms			= 300
  };
  
  const lws_led_sequence_def_t lws_pwmseq_linear_wipe = {
  	.func			= lws_led_func_linear,
  	.ledphase_offset	= 0,
  	.ledphase_total		= LWS_LED_FUNC_PHASE - 1,
  	.ms			= 300
  };
  
  const lws_led_sequence_def_t lws_pwmseq_sine_endless_slow = {
  	.func			= lws_led_func_sine,
  	.ledphase_offset	= 0, /* already at 0 amp at 0 phase */
  	.ledphase_total		= LWS_SEQ_LEDPHASE_TOTAL_ENDLESS,
  	.ms			= 1500
  };
  
  const lws_led_sequence_def_t lws_pwmseq_sine_endless_fast = {
  	.func			= lws_led_func_sine,
  	.ledphase_offset	= 0, /* already at 0 amp at 0 phase */
  	.ledphase_total		= LWS_SEQ_LEDPHASE_TOTAL_ENDLESS,
  	.ms			= 750
  };
  