关于WS2812

WS2812/2811只需一根信号线就能控制灯带上所有led。多个灯带间可以通过串联轻松延长。在30hz的刷新频率下一个信号线能够控制至多500个led。
WS2812B是我做嵌入式软件的第一个项目，这里资料参考了WS2812灯珠（四）—实现全彩呼吸灯效果，非常感谢这位博主给出的教程和相关源码，但是测试下来有些问题，自己检查修改了一下，在stm32f030f4上可以完美的跑起来。

关于HSV

HSV(Hue, Saturation, Value)是根据颜色的直观特性创建的一种颜色空间, 由色调(H)，饱和度(S)，明度(V)三个参数组成，与传统的RGB相比它可以非常方便的通过调整明度来平滑的显示颜色亮度变化.

比较最大最小值的函数

static float min(float a, float b, float c)
{
  float m;
  m = a < b ? a : b;
  return (m < c ? m : c);
}

static float max(float a, float b, float c)
{
  float m;
  m = a > b ? a : b;
  return (m > c ? m : c);
}

RGB转换为HSV

void rgb2hsv(uint8_t g, uint8_t r, uint8_t b, float *h, float *s, float *v)
{
  float red, green ,blue;
  float cmax, cmin, delta;

  red =   (float)r / 255;
  green = (float)g / 255;
  blue =  (float)b / 255;

  cmax = max(red, green, blue);
  cmin = min(red, green, blue);
  delta = cmax - cmin;

  /* H */
  if(delta == 0)
  {
    *h = 0;
  }
  else
  {
    if(cmax == red)
    {
      if(green >= blue)
      {
        *h = 60 * ((green - blue) / delta);
      }
      else
      {
        *h = 60 * ((green - blue) / delta) + 360;
      }
    }
    else if(cmax == green)
    {
      *h = 60 * ((blue - red) / delta + 2);
    }
    else if(cmax == blue)
    {
      *h = 60 * ((red - green) / delta + 4);
    }
  }

  /* S */
  if(cmax == 0)
  {
    *s = 0;
  }
  else
  {
    *s = delta / cmax;
  }

  /* V */
  *v = cmax;
}

HSV转换为RGB

void hsv2rgb(float h, float s, float v, uint8_t *g, uint8_t *r, uint8_t *b)
{
  if(s == 0)
  {
    *r=*g=*b=v;
  }
  else
  {
    float H = h / 60;
    int hi = (int)H;
    float f = H - hi;
    float p = v * (1 - s);
    float q = v * (1 - f * s);
    float t = v * (1- (1 - f) * s);
    switch (hi){
      case 0:
        *r = (int)(v * 255.0 + 0.5);
        *g = (int)(t * 255.0 + 0.5);
        *b = (int)(p * 255.0 + 0.5);
        break;
      case 1:
        *r = (int)(q * 255.0 + 0.5);
        *g = (int)(v * 255.0 + 0.5);
        *b = (int)(p * 255.0 + 0.5);
        break;
      case 2:
        *r = (int)(p * 255.0 + 0.5);
        *g = (int)(v * 255.0 + 0.5);
        *b = (int)(t * 255.0 + 0.5);
        break;
      case 3:
        *r = (int)(p * 255.0 + 0.5);
        *g = (int)(q * 255.0 + 0.5);
        *b = (int)(v * 255.0 + 0.5);
        break;
      case 4:
        *r = (int)(t * 255.0 + 0.5);
        *g = (int)(p * 255.0 + 0.5);
        *b = (int)(v * 255.0 + 0.5);
        break;
      case 5:
        *r = (int)(v * 255.0 + 0.5);
        *g = (int)(p * 255.0 + 0.5);
        *b = (int)(q * 255.0 + 0.5);
        break;
			default:
				break;
    }
  }
}