关于 php使用扩展控制树莓派io 驱动超声波测距

<?php
/**
 * Created by PhpStorm.
 * User: tioncico
 * Date: 19-7-6
 * Time: 下午4:45
 */
define('PI_TRIG',0);
define('PI_ECHO',1);

if (wiringPiSetup()===false){
    echo "初始化错误！";
    die;
}
//初始化引脚
ultraInit();
while (1) {
    //测距
    $dis = disMeasure();
    printf("distance = %0.2f cm\n", $dis);
    piDelay(1000);
}

function ultraInit(){
    pinMode(PI_ECHO, PI_INPUT);
    pinMode(PI_TRIG, PI_OUTPUT);
}

function disMeasure(){
    //先关闭脉冲，初始化
    digitalWrite(PI_TRIG,PI_LOW);
    //等待2微秒
    piDelayMicroseconds(2);
    //发出超声波脉冲
    digitalWrite(PI_TRIG, PI_HIGH);
    piDelayMicroseconds(10);
    //等待10秒，关闭脉冲
    digitalWrite(PI_TRIG, PI_LOW);
    //关闭之后，马上开始判断获取声波
    while (!(digitalRead(PI_ECHO) == 1));
    $startTime = piMicros();
    //如果获取不到了，说明已经接收完毕
    while (!(digitalRead(PI_ECHO) == 0));
    $endTime = piMicros();

    //声音在空气中传播是34000cm/s, 1000000微秒是1秒，去掉来回的声波时间，求出距离
    $dis = ($endTime - $startTime) / 1000000 * 34000 / 2;  //求出距离
    return $dis;
}