开发板上闪烁的LED如同新手村的篝火，为每一位嵌入式开发者照亮通往硬件世界的探索之路。

开发板上有2个user led，对应
/sys/class/leds/user-led0
/sys/class/leds/user-led1

一、命令点亮LED

用命令点亮它：
cd /sys/class/leds/user-led0
echo 1 > brightness

熄灭它：
echo 0 > brightness

二、led_flash例程

例程位置：Demo/base-demo/led_flash

闪灯部分

while (!g_quit) {
        /* Turn on LEDs */
        for (i = 0; i < num; i++) {
            /* Set the LED brightness value to 1 to turn on the led */
            snprintf(cmd, 64, "echo 1 > %s/brightness", g_leds[i]);
            if (system(cmd) != 0) {
                fprintf(stderr, "Error: Failed to turn on %s\n", g_leds[i]);
                exit(EXIT_FAILURE);
            }
        }

        /* Keep the LEDs on for 500 ms */
        usleep(500 * 1000);

        /* Turn off LEDs */
        for (i = 0; i < num; i++) {
            /* Set the LED brightness value to 0 to turn off the LED */
            snprintf(cmd, 64, "echo 0 > %s/brightness", g_leds[i]);
            if (system(cmd) != 0) {
                fprintf(stderr, "Error: Failed to turn off %s\n", g_leds[i]);
                exit(EXIT_FAILURE);
            }
        }

        /* Keep the LEDs off for 500 ms */
        usleep(500 * 1000);
    }

根据命令行输入的-n 灯数，通过system发送
echo 1 > %s/brightness点亮LED
echo 0 > %s/brightness熄灭LED

三、通过其他GPIO点亮LED

从开发板板上找一个GPIO

就用GPIO1_C1吧。
GPIO1_C1对应引脚编号=321+82+1=49

使能引脚
echo 49 > /sys/class/gpio/export
设置引脚为输入模式
echo out > /sys/class/gpio/gpio49/direction
设置引脚为低电平
echo 0 > /sys/class/gpio/gpio49/value
设置引脚为高电平
echo 1 > /sys/class/gpio/gpio49/value
复位引脚
echo 49 > /sys/class/gpio/unexport

四、使用libgpiod库

libgpiod 是一种字符设备接口，GPIO 访问控制是通过操作字符设备文件（比如 /dev/gpiodchip0 ）
实现的，并通过 libgpiod 提供一些命令工具、c 库以及 python 封装

安装 libgpiod 库及头文件
sudo apt install libgpiod-dev3

安装 gpiod 命令行工具
sudo apt install gpiod

libgpiod命令行工具：

点亮GPIO1_C1：
gpioset -c 1 17=0
熄灭GPIO1_C1：
gpioset -c 1 17=1

通过程序闪烁GPIO1_C1

// SPDX-License-Identifier: GPL-2.0-or-later
// SPDX-FileCopyrightText: 2023 Kent Gibson <warthog618@gmail.com>

/* Minimal example of toggling a single line. */

#include <errno.h>
#include <gpiod.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static struct gpiod_line_request *
request_output_line(const char *chip_path, unsigned int offset,
		    enum gpiod_line_value value, const char *consumer)
{
	struct gpiod_request_config *req_cfg = NULL;
	struct gpiod_line_request *request = NULL;
	struct gpiod_line_settings *settings;
	struct gpiod_line_config *line_cfg;
	struct gpiod_chip *chip;
	int ret;

	chip = gpiod_chip_open(chip_path);
	if (!chip)
		return NULL;

	settings = gpiod_line_settings_new();
	if (!settings)
		goto close_chip;

	gpiod_line_settings_set_direction(settings,
					  GPIOD_LINE_DIRECTION_OUTPUT);
	gpiod_line_settings_set_output_value(settings, value);

	line_cfg = gpiod_line_config_new();
	if (!line_cfg)
		goto free_settings;

	ret = gpiod_line_config_add_line_settings(line_cfg, &offset, 1,
						  settings);
	if (ret)
		goto free_line_config;

	if (consumer) {
		req_cfg = gpiod_request_config_new();
		if (!req_cfg)
			goto free_line_config;

		gpiod_request_config_set_consumer(req_cfg, consumer);
	}

	request = gpiod_chip_request_lines(chip, req_cfg, line_cfg);

	gpiod_request_config_free(req_cfg);

free_line_config:
	gpiod_line_config_free(line_cfg);

free_settings:
	gpiod_line_settings_free(settings);

close_chip:
	gpiod_chip_close(chip);

	return request;
}

static enum gpiod_line_value toggle_line_value(enum gpiod_line_value value)
{
	return (value == GPIOD_LINE_VALUE_ACTIVE) ? GPIOD_LINE_VALUE_INACTIVE :
						    GPIOD_LINE_VALUE_ACTIVE;
}

static const char * value_str(enum gpiod_line_value value)
{
	if (value == GPIOD_LINE_VALUE_ACTIVE)
		return "Active";
	else if (value == GPIOD_LINE_VALUE_INACTIVE) {
		return "Inactive";
	} else {
		return "Unknown";
	}
}

int main(void)
{
	/* Example configuration - customize to suit your situation. */
	static const char *const chip_path = "/dev/gpiochip1";
	static const unsigned int line_offset = 17;

	enum gpiod_line_value value = GPIOD_LINE_VALUE_ACTIVE;
	struct gpiod_line_request *request;

	request = request_output_line(chip_path, line_offset, value,
				      "toggle-line-value");
	if (!request) {
		fprintf(stderr, "failed to request line: %s\n",
			strerror(errno));
		return EXIT_FAILURE;
	}

	for (;;) {
		printf("%d=%s\n", line_offset, value_str(value));
		sleep(1);
		value = toggle_line_value(value);
		gpiod_line_request_set_value(request, line_offset, value);
	}

	gpiod_line_request_release(request);

	return EXIT_SUCCESS;
}