仅通过我在网上找到的网页脚本执行简单的打开LED指示灯,似乎在跟随它们的shell_exec命令之后执行了echo命令,这是否有原因?基本上,打开和关闭的速度足够快,无法真正注意到,但是闪烁的回声仅在闪烁序列完成后才出现。
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>WIFI Controlled LED</title>
</head>
<body>
<center><b><font size = '20'>Control LED:</b>
<form method="get" action="index.php">
<input type="submit" style = "font-size: 16 pt" value="OFF" name="off">
<input type="submit" style = "font-size: 16 pt" value="ON" name="on">
<input type="submit" style = "font-size: 16 pt" value="BLINK" name="blink">
</form>
<?php
shell_exec("/usr/local/bin/gpio -g mode 17 out");
if(isset($_GET['off']))
{
echo "LED is off";
shell_exec("/usr/local/bin/gpio -g write 17 0");
}
else if(isset($_GET['on']))
{
echo "LED is on";
shell_exec("/usr/local/bin/gpio -g write 17 1");
}
else if(isset($_GET['blink']))
{
echo "LED is blinking";
for($x = 0;$x<=4;$x++)
{
shell_exec("/usr/local/bin/gpio -g write 17 1");
sleep(1);
shell_exec("/usr/local/bin/gpio -g write 17 0");
sleep(1);
}
}
?>
</center></font>
</body>
</html>