Unable to drive LEDC PWM after software reset

[maldus]

Hello everyone,
I am using an ESP32-WROOM-32D module to drive a 320x240 color LCD via SPI. I also drive the display's backlight with a simple output pin on IO04.

To change the backlight smoothly I'm using the ledc module and everything works as expected until a software reset occurs. For several reasons I need to reset my device with the `esp_restart` function, and after the reset the backlight is dead.
Everything else works as expected and I could confirm that the problem is due to backlight control by switching from the ledc module to simple IO control (in which case there are no issues).

I would say either the ledc module or the IO4 itself remains in an incosistent state after a software reset. Hardware resets behave normally.

This is the initialization code that I'm using:

Code: Select all

static void display_backlight_init() {
    ledc_timer_config_t ledc_timer = {
        .duty_resolution = LEDC_TIMER_8_BIT,        // resolution of PWM duty
        .freq_hz         = 1000,                    // frequency of PWM signal
        .speed_mode      = LEDC_LOW_SPEED_MODE,     // timer mode
        .timer_num       = LEDC_TIMER_2,            // timer index
        .clk_cfg         = LEDC_AUTO_CLK,           // Auto select the source clock
    };
    ledc_timer_config(&ledc_timer);

    ledc_channel_config_t ledc_channel = {.channel    = LEDC_CHANNEL_1,
                                          .duty       = 0xFF,
                                          .gpio_num   = GPIO_NUM_4,
                                          .speed_mode = LEDC_LOW_SPEED_MODE,
                                          .hpoint     = 0,
                                          .timer_sel  = LEDC_TIMER_2};
    ledc_channel_config(&ledc_channel);
    ledc_stop(LEDC_LOW_SPEED_MODE, LEDC_CHANNEL_1, 0);
    display_set_backlight(40);
}

void display_set_backlight(int percentage) {
    int duty = (percentage * 0xFF) / 100;
    if (duty != ledc_get_duty(LEDC_LOW_SPEED_MODE, LEDC_CHANNEL_1)) {
        ledc_set_duty(LEDC_LOW_SPEED_MODE, LEDC_CHANNEL_1, duty);
        ledc_update_duty(LEDC_LOW_SPEED_MODE, LEDC_CHANNEL_1);
    }
}

Additionally, before resetting the module I tried to stop the ledc module with the `ledc_stop(LEDC_LOW_SPEED_MODE, LEDC_CHANNEL_1, 0);` function call.
Is there any additional step I should take to properly re-initialize my backlight control?