编写至少四个LED不同亮度同时出现 编写利用定时器产生不同占空比的PWM控制单个LED的呼吸灯效果（亮度从最亮到灭，再从灭到最亮） 分别用两个按键控制1只高亮的LED亮度从亮到灭和从灭到亮

1. 编写至少四个LED不同亮度同时出现：

#include <stdio.h>
#include <wiringPi.h>

#define LED_PIN_1 0
#define LED_PIN_2 1
#define LED_PIN_3 2
#define LED_PIN_4 3

int main(void)
{
    if (wiringPiSetup() == -1)
    {
        return 1;
    }

    pinMode(LED_PIN_1, OUTPUT);
    pinMode(LED_PIN_2, OUTPUT);
    pinMode(LED_PIN_3, OUTPUT);
    pinMode(LED_PIN_4, OUTPUT);

    digitalWrite(LED_PIN_1, HIGH);
    delay(100);
    digitalWrite(LED_PIN_2, HIGH);
    delay(100);
    digitalWrite(LED_PIN_3, HIGH);
    delay(100);
    digitalWrite(LED_PIN_4, HIGH);
    delay(100);

    digitalWrite(LED_PIN_1, LOW);
    delay(100);
    digitalWrite(LED_PIN_2, LOW);
    delay(100);
    digitalWrite(LED_PIN_3, LOW);
    delay(100);
    digitalWrite(LED_PIN_4, LOW);
    delay(100);

    return 0;
}

2. 编写利用定时器产生不同占空比的PWM控制单个LED的呼吸灯效果：

#include <stdio.h>
#include <wiringPi.h>
#include <softPwm.h>

#define LED_PIN 0
#define PWM_RANGE 100

int main(void)
{
    if (wiringPiSetup() == -1)
    {
        return 1;
    }

    pinMode(LED_PIN, OUTPUT);
    softPwmCreate(LED_PIN, 0, PWM_RANGE);

    int i;
    while (1)
    {
        for (i = 0; i <= PWM_RANGE; i++)
        {
            softPwmWrite(LED_PIN, i);
            delay(5);
        }

        for (i = PWM_RANGE; i >= 0; i--)
        {
            softPwmWrite(LED_PIN, i);
            delay(5);
        }
    }

    return 0;
}

3. 用两个按键控制1只高亮的LED亮度从亮到灭和从灭到亮：

#include <stdio.h>
#include <wiringPi.h>
#include <softPwm.h>

#define LED_PIN 0
#define PWM_RANGE 100
#define BUTTON_UP 1
#define BUTTON_DOWN 2

int main(void)
{
    if (wiringPiSetup() == -1)
    {
        return 1;
    }

    pinMode(LED_PIN, OUTPUT);
    softPwmCreate(LED_PIN, 0, PWM_RANGE);
    pinMode(BUTTON_UP, INPUT);
    pinMode(BUTTON_DOWN, INPUT);

    int brightness = 0;
    int direction = 1;
    while (1)
    {
        if (digitalRead(BUTTON_UP) == LOW)
        {
            brightness++;
            if (brightness > PWM_RANGE)
            {
                brightness = PWM_RANGE;
            }
            softPwmWrite(LED_PIN, brightness);
            delay(10);
        }
        else if (digitalRead(BUTTON_DOWN) == LOW)
        {
            brightness--;
            if (brightness < 0)
            {
                brightness = 0;
            }
            softPwmWrite(LED_PIN, brightness);
            delay(10);
        }
        else
        {
            if (direction == 1)
            {
                brightness++;
                if (brightness >= PWM_RANGE)
                {
                    direction = -1;
                }
            }
            else
            {
                brightness--;
                if (brightness <= 0)
                {
                    direction = 1;
                }
            }
            softPwmWrite(LED_PIN, brightness);
            delay(10);
        }
    }

    return 0;
}

在这个例子中，我们使用了两个按键来控制 LED 的亮度变化。一个按键用来增加亮度，另一个用来减小亮度。同时，LED 也会呼吸灯效果地变化。我们使用了一个 `direction` 变量来控制 LED 的亮度变化方向。