Test for WS2812b, can not work

main.c

/*
 * SPDX-FileCopyrightText: 2021-2023 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Unlicense OR CC0-1.0
 */
/* ULP-RISC-V example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.

   This code runs on ULP-RISC-V  coprocessor
*/

#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include "ulp_riscv.h"
#include "ulp_riscv_utils.h"
#include "ulp_riscv_gpio.h"

#define EXAMPLE_WS2812B_GPIO GPIO_NUM_4
#define LED_NUM 12

typedef enum {
    GPIO_NOT_INITIATED,
    GPIO_INITIATED,
} gpio_state_t;

gpio_state_t state = GPIO_NOT_INITIATED;
uint8_t led_buffer[LED_NUM];

void ws2812b_write_bit(bool bit)
{
    // time critical section
    if (bit) { //High: long high, short low
        // time critical section
        REG_SET_FIELD(EXAMPLE_WS2812B_GPIO, RTC_GPIO_OUT_DATA_W1TS, BIT(0));
        ulp_riscv_delay_cycles(8); // wait additional 8 * 57 nanoseconds
        REG_SET_FIELD(EXAMPLE_WS2812B_GPIO, RTC_GPIO_OUT_DATA_W1TC, BIT(0));
        // end of time critical section
    }
    else{ //Low: short high, long low
        // time critical section
        REG_SET_FIELD(EXAMPLE_WS2812B_GPIO, RTC_GPIO_OUT_DATA_W1TS, BIT(0));
        REG_SET_FIELD(EXAMPLE_WS2812B_GPIO, RTC_GPIO_OUT_DATA_W1TC, BIT(0));
        // end of time critical section
    }
    // the "low" period must be shorter than 5 microseconds, and must be  at least 900 nanoseconds
}

static void ws2812b_write_byte(uint8_t data)
{
    for (int i = 0; i < 8; i++) {
        ws2812b_write_bit((data >> i) & 0x1);
    }
}

static void ws2812b_write_buffer()
{
    for (int i = 0; i < LED_NUM; i++) {
        ws2812b_write_bit(led_buffer[i]);
    }
}

int main (void)
{

    switch (state) {
    case GPIO_NOT_INITIATED:
        /* Setup GPIO used for WS2812 */
        ulp_riscv_gpio_init(EXAMPLE_WS2812B_GPIO);
        ulp_riscv_gpio_output_enable(EXAMPLE_WS2812B_GPIO);
        ulp_riscv_gpio_set_output_mode(EXAMPLE_WS2812B_GPIO, RTCIO_MODE_OUTPUT_OD);
        ulp_riscv_gpio_pullup(EXAMPLE_WS2812B_GPIO);
        ulp_riscv_gpio_pulldown_disable(EXAMPLE_WS2812B_GPIO);

        ws2812b_write_buffer();
        state = GPIO_INITIATED;
        break;

    case GPIO_INITIATED:
        ws2812b_write_buffer();

        break;
    }

    /* ulp_riscv_halt() is called automatically when main exits,
       main will be executed again at the next timeout period,
       according to ulp_set_wakeup_period()
     */
    return 0;
}