The LED PWM module can use RTC8M_CLK as a clock source when APB_CLK is disabled. In other words,
when the system is in low-power consumption mode (see Power Management Chapter), normal peripherals will
be halted (APB_CLK is turned off), but the LED PWM can work normally via RTC8M_CLK.
Code: Select all
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/ledc.h"
#include "esp_err.h"
#include "esp_pm.h"
#include "esp_sleep.h"
#include "driver/uart.h"
#include "esp32/rom/uart.h"
#define LEDC_LS_TIMER LEDC_TIMER_0
#define LEDC_LS_MODE LEDC_LOW_SPEED_MODE
#define LEDC_LS_CH2_GPIO (19)
#define LEDC_LS_CH2_CHANNEL LEDC_CHANNEL_2
#define LEDC_TEST_CH_NUM (1)
#define LEDC_TEST_DUTY (4000)
#define LEDC_TEST_FADE_TIME (3000)
void app_main()
{
int ch;
ledc_timer_config_t ledc_timer = {
.duty_resolution = LEDC_TIMER_13_BIT, // resolution of PWM duty
.freq_hz = 100, // frequency of PWM signal
.speed_mode = LEDC_LS_MODE, // timer mode
.timer_num = LEDC_LS_TIMER, // timer index
.clk_cfg = LEDC_USE_RTC8M_CLK, // Auto select the source clock
};
ledc_timer_config(&ledc_timer);
ledc_channel_config_t ledc_channel[LEDC_TEST_CH_NUM] = {
{
.channel = LEDC_LS_CH2_CHANNEL,
.duty = 0,
.gpio_num = LEDC_LS_CH2_GPIO,
.speed_mode = LEDC_LS_MODE,
.hpoint = 0,
.timer_sel = LEDC_LS_TIMER
},
};
for (ch = 0; ch < LEDC_TEST_CH_NUM; ch++) {
ledc_channel_config(&ledc_channel[ch]);
}
ledc_fade_func_install(0);
printf("Frequency %u Hz\n", ledc_get_freq(LEDC_LS_MODE, LEDC_LS_TIMER));
while (1) {
printf("1. LEDC fade up to duty = %d\n", LEDC_TEST_DUTY);
for (ch = 0; ch < LEDC_TEST_CH_NUM; ch++) {
ledc_set_fade_with_time(ledc_channel[ch].speed_mode,
ledc_channel[ch].channel, LEDC_TEST_DUTY, LEDC_TEST_FADE_TIME);
ledc_fade_start(ledc_channel[ch].speed_mode,
ledc_channel[ch].channel, LEDC_FADE_NO_WAIT);
}
vTaskDelay(LEDC_TEST_FADE_TIME / portTICK_PERIOD_MS);
printf("Sleep\n");
esp_sleep_enable_timer_wakeup(10000000);
esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_ON);
fflush(stdout);
uart_tx_wait_idle(CONFIG_CONSOLE_UART_NUM);
esp_light_sleep_start();
}
}Code: Select all
rtc_clk_slow_freq_set(RTC_SLOW_FREQ_8MD256);