musicmouse/espmusicmouse/lib/leds/LedControl.cpp

#include "LedControl.h"
#include "driver/rmt.h"
#include "esp32_digital_led_lib.h"
#include "Arduino.h"

#define HSV_SECTION_6 (0x20)
#define HSV_SECTION_3 (0x40)

static ColorRGB hsv2rgb(const ColorHSV &hsv)
{
  // Convert hue, saturation and brightness ( HSV/HSB ) to RGB
  // "Dimming" is used on saturation and brightness to make
  // the output more visually linear.

  // Apply dimming curves
  uint8_t value = hsv.v;
  uint8_t saturation = hsv.s;

  // The brightness floor is minimum number that all of
  // R, G, and B will be set to.
  uint8_t invsat = 255 - saturation;
  uint8_t brightness_floor = (value * invsat) / 256;

  // The color amplitude is the maximum amount of R, G, and B
  // that will be added on top of the brightness_floor to
  // create the specific hue desired.
  uint8_t color_amplitude = value - brightness_floor;

  // Figure out which section of the hue wheel we're in,
  // and how far offset we are withing that section
  uint8_t section = hsv.h / HSV_SECTION_3; // 0..2
  uint8_t offset = hsv.h % HSV_SECTION_3;  // 0..63

  uint8_t rampup = offset;                         // 0..63
  uint8_t rampdown = (HSV_SECTION_3 - 1) - offset; // 63..0

  // We now scale rampup and rampdown to a 0-255 range -- at least
  // in theory, but here's where architecture-specific decsions
  // come in to play:
  // To scale them up to 0-255, we'd want to multiply by 4.
  // But in the very next step, we multiply the ramps by other
  // values and then divide the resulting product by 256.
  // So which is faster?
  //   ((ramp * 4) * othervalue) / 256
  // or
  //   ((ramp    ) * othervalue) /  64
  // It depends on your processor architecture.
  // On 8-bit AVR, the "/ 256" is just a one-cycle register move,
  // but the "/ 64" might be a multicycle shift process. So on AVR
  // it's faster do multiply the ramp values by four, and then
  // divide by 256.
  // On ARM, the "/ 256" and "/ 64" are one cycle each, so it's
  // faster to NOT multiply the ramp values by four, and just to
  // divide the resulting product by 64 (instead of 256).
  // Moral of the story: trust your profiler, not your insticts.

  // Since there's an AVR assembly version elsewhere, we'll
  // assume what we're on an architecture where any number of
  // bit shifts has roughly the same cost, and we'll remove the
  // redundant math at the source level:

  //  // scale up to 255 range
  //  //rampup *= 4; // 0..252
  //  //rampdown *= 4; // 0..252

  // compute color-amplitude-scaled-down versions of rampup and rampdown
  uint8_t rampup_amp_adj = (rampup * color_amplitude) / (256 / 4);
  uint8_t rampdown_amp_adj = (rampdown * color_amplitude) / (256 / 4);

  // add brightness_floor offset to everything
  uint8_t rampup_adj_with_floor = rampup_amp_adj + brightness_floor;
  uint8_t rampdown_adj_with_floor = rampdown_amp_adj + brightness_floor;

  if (section)
  {
    if (section == 1)
      return ColorRGB{brightness_floor, rampdown_adj_with_floor, rampup_adj_with_floor};
    else
      return ColorRGB{rampup_adj_with_floor, brightness_floor, rampdown_adj_with_floor};
  }
  else
    return ColorRGB{rampdown_adj_with_floor, rampup_adj_with_floor, brightness_floor};
}

LedStrip::LedStrip(int numLeds, int pin)
    : numLeds_(numLeds), pin_(pin)
{
  cfg = {.rmtChannel = 0, .gpioNum = pin, .ledType = LED_SK6812W_V1, .brightLimit = 24, .numPixels = numLeds};
  strands[0] = &cfg;
}

void LedStrip::begin()
{
  digitalLeds_initDriver();
  gpioSetup(cfg.gpioNum, OUTPUT, LOW);

  int rc = digitalLeds_addStrands(strands, 1);
  if (rc)
    Serial.println("LEDs: Error during init");
}

void LedStrip::clear()
{
  digitalLeds_resetPixels(strands, 1);
}

int LedStrip::normalizeLedIdx(int i)
{
  while (i < 0)
    i += numLeds_;
  while (i >= numLeds_)
    i -= numLeds_;
  return i;
}

void LedStrip::setColor(int led, int r, int g, int b, int w)
{
  strands[0]->pixels[led] = pixelFromRGBW(r, g, b, w);
}

void LedStrip::transmit()
{
  digitalLeds_drawPixels(strands, 1);
}

void LedStrip::setAll(int r, int g, int b, int w)
{
  for (int i = 0; i < numLeds_; ++i)
    setColor(i, r, g, b, w);
}

void LedStrip::setRange(int begin, int end, int r, int g, int b, int w)
{
  for (int i = begin; i < min(end, numLeds_); ++i)
    setColor(i, r, g, b, w);
}

void LedStrip::setColor(int led, const ColorRGB &color)
{
  setColor(led, color.r, color.g, color.b, 0);
}

void LedStrip::setColor(int led, const ColorHSV &color)
{
  setColor(led, hsv2rgb(color));
}