ESP32 RMT Carrier always_on

void rmt_tx_init() 

{

    rmt_channel_handle_t tx_chan = NULL;

    rmt_tx_channel_config_t tx_chan_config = {

        .clk_src = RMT_CLK_SRC_DEFAULT,   // select source clock

        .gpio_num = 33,                   // GPIO number

        .mem_block_symbols = 64,          // memory block size, 64 * 4 = 256 Bytes

        .resolution_hz = 1 * 1000 * 1000, // 1 MHz tick resolution, i.e., 1 tick = 1 µs

        .trans_queue_depth = 4,           // set the number of transactions that can pend in the background

        .flags.invert_out = false,        // do not invert output signal

        .flags.with_dma = false,          // do not need DMA backend

    };

    ESP_ERROR_CHECK(rmt_new_tx_channel(&tx_chan_config, &tx_chan));

    rmt_carrier_config_t tx_carrier_cfg = {

        .duty_cycle = 0.33,                 // duty cycle 33%

        .frequency_hz = 38000,              // 38 KHz

        .flags.polarity_active_low = false, // carrier should be modulated to high level

        .always_on = true,                  // If set, the carrier can always exist even there's not transfer undergoing

    };

    // modulate carrier to TX channel

    ESP_ERROR_CHECK(rmt_apply_carrier(tx_chan, &tx_carrier_cfg));

}