#include <driver/ledc.h>
#include <hal/ledc_types.h>

// fade LED PIN (replace with LED_BUILTIN constant for built-in LED)
#define LED_PIN            5

int freq = 1;   // how bright the LED is
ledc_timer_bit_t bits = LEDC_TIMER_8_BIT;
ledc_mode_t mode = LEDC_LOW_SPEED_MODE;
ledc_timer_t timer = LEDC_TIMER_0;
ledc_channel_t channel = LEDC_CHANNEL_0;
ledc_clk_cfg_t clockcfg = LEDC_USE_REF_TICK;

void setup() {
  Serial.begin(115200);

  ledc_timer_config_t timercfg = {
    .speed_mode = mode,
    .duty_resolution = bits,
    .timer_num = timer,
    .freq_hz = 1000,
    .clk_cfg = clockcfg
  };
  ledc_timer_config(&timercfg);

  ledc_channel_config_t channelcfg = {
    .gpio_num = LED_PIN,
    .speed_mode = mode,
    .channel = channel,
    .timer_sel = timer,
    .duty = 1 << (bits - 1),
              .hpoint = 0,
    .flags = {.output_invert = 0}
  };
  ledc_channel_config(&channelcfg);
}

void loop() {
  uint64_t clk = LEDC_REF_CLK_HZ << (8-bits);
  Serial.print(clk);Serial.print(" ");
  uint32_t div = (uint64_t)(LEDC_REF_CLK_HZ << (8-bits)) / freq;
  Serial.print(div);Serial.print(" ");
  ledc_timer_set(mode, timer, div, bits, (ledc_clk_src_t) clockcfg);
  Serial.print(freq);
  Serial.print("/");
  Serial.println(ledc_get_freq(mode, timer));

  freq *= 2;
  if (freq > 20000) {
    delay(10000);
    freq = 1;
  }

  delay(600);
}