Hue rotation of an RGB LED using ESP-IDF framework

esp_idf_hue_rotation.c

// color_utils.h
#ifndef _COLOR_UTILS_
#define _COLOR_UTILS_

typedef struct RGB {
	unsigned char r;
	unsigned char g;
	unsigned char b;
} rgb_t;

typedef struct HSV {
	double h;
	double s;
	double v;
} hsv_t;

rgb_t hsv_to_rgb(hsv_t hsv);

#endif

//color_utils.c
#include <math.h>
#include "color_utils.h"

rgb_t hsv_to_rgb(hsv_t hsv) {
	double r = 0, g = 0, b = 0;

	if (hsv.s == 0)
	{
		r = hsv.v;
		g = hsv.v;
		b = hsv.v;
	}
	else
	{
		int i;
		double f, p, q, t;

		if (hsv.h == 360)
			hsv.h = 0;
		else
			hsv.h = hsv.h / 60;

		i = (int)trunc(hsv.h);
		f = hsv.h - i;

		p = hsv.v * (1.0 - hsv.s);
		q = hsv.v * (1.0 - (hsv.s * f));
		t = hsv.v * (1.0 - (hsv.s * (1.0 - f)));

		switch (i)
		{
		case 0:
			r = hsv.v;
			g = t;
			b = p;
			break;

		case 1:
			r = q;
			g = hsv.v;
			b = p;
			break;

		case 2:
			r = p;
			g = hsv.v;
			b = t;
			break;

		case 3:
			r = p;
			g = q;
			b = hsv.v;
			break;

		case 4:
			r = t;
			g = p;
			b = hsv.v;
			break;

		default:
			r = hsv.v;
			g = p;
			b = q;
			break;
		}

	}

	rgb_t rgb = {
    .r = r * 255,
    .g = g * 255,
    .b = b * 255
  };

	return rgb;
}

//main.c

#include <stdio.h>
#include "driver/gpio.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/ledc.h"

#include "color_utils.h"

#define GPIO_RED    14
#define GPIO_GREEN  15
#define GPIO_BLUE   27

static ledc_channel_config_t r_ledc_channel;
static ledc_channel_config_t g_ledc_channel;
static ledc_channel_config_t b_ledc_channel;

static void config_ledc_channel(ledc_channel_config_t* c, int gpio_num, ledc_channel_t channel) {
  c->channel = channel;
  c->duty = 0;
  c->gpio_num = gpio_num;
  c->speed_mode = LEDC_HIGH_SPEED_MODE;
  c->hpoint = 0;
  c->timer_sel = LEDC_TIMER_0;
  ledc_channel_config(c);
}

static void set_ledc_duty(ledc_channel_config_t c, int duty) {
  ledc_set_duty(c.speed_mode, c.channel, duty);
  ledc_update_duty(c.speed_mode, c.channel);
}

static void init_hw(void) {
  ledc_timer_config_t ledc_timer = {
    .duty_resolution = LEDC_TIMER_8_BIT,
    .freq_hz = 1000,
    .speed_mode = LEDC_HIGH_SPEED_MODE,
    .timer_num = LEDC_TIMER_0,
    .clk_cfg = LEDC_AUTO_CLK
  };
  ledc_timer_config(&ledc_timer);

  config_ledc_channel(&r_ledc_channel, GPIO_RED, LEDC_CHANNEL_0);
  config_ledc_channel(&g_ledc_channel, GPIO_GREEN, LEDC_CHANNEL_1);
  config_ledc_channel(&b_ledc_channel, GPIO_BLUE, LEDC_CHANNEL_2);
}

static hsv_t hsv = {
  .h = 0,
  .s = 1.0,
  .v = 1.0
};

void loop(void) {
  hsv.h++;
  if (hsv.h == 360) {
    hsv.h = 0;
  }

  rgb_t rgb = hsv_to_rgb(hsv);

  set_ledc_duty(r_ledc_channel, 255 - rgb.r);
  set_ledc_duty(g_ledc_channel, 255 - rgb.g);
  set_ledc_duty(b_ledc_channel, 255 - rgb.b);

  vTaskDelay(10 / portTICK_PERIOD_MS);
}

void app_main() {
  init_hw();
  while (1) {
    loop();
  }
}