deviceSet("/dev/tty.usbserial-A4001nU7"); //Set the serial port parameters. The documentation says 9600 8-N-1, so $serial->confBaudRate(9600); //Baud rate: 9600 $serial->confParity("none"); //Parity (this is the "N" in "8-N-1") $serial->confCharacterLength(8); //Character length (this is the "8" in "8-N-1") $serial->confStopBits(1); //Stop bits (this is the "1" in "8-N-1") // Ask Arduino if the LED is ON or OFF $serial->deviceOpen(); $serial->sendMessage(chr(10)); // start transmission $serial->sendMessage("2"); $serial->sendMessage(chr(13)); // end transmission $read = $serial->readPort(); // waiting for reply $led1 = $read; $led1 = (int)$led1; //We're done, so close the serial port again $serial->deviceClose(); // Add some xhtml and CSS to display an ON/OFF button echo ""; echo ""; echo ""; echo ""; echo "Toggle LED on Arduino"; echo ""; echo ""; echo ""; // if LED is OFF (0), then display the ON button if ($led1 === 0) { echo "

"; } // if LED is ON (1), then display the OFF button if ($led1 === 1) { echo "

"; } echo ""; echo ""; //check the GET action var to see if an action is to be performed if (isset($_GET['action'])) { //Action required //Now we "open" the serial port so we can write to it $serial->deviceOpen(); $serial->sendMessage(chr(10)); // start Transmission //Do the request if ($_GET['action'] == "on") { echo "

"; // toggle the button $serial->sendMessage("1"); // turn LED ON } else if ($_GET['action'] == "off") { echo "

"; // toggle the button $serial->sendMessage("0"); // turn LED OFF } $serial->sendMessage(chr(13)); // end Transmission //We're done, so close the serial port again $serial->deviceClose(); } ?> Here's the last version I used I think they are the same but I'm not 100% sure deviceSet("/dev/tty.usbserial-A4001nU7"); //Set the serial port parameters. The documentation says 9600 8-N-1, so $serial->confBaudRate(9600); //Baud rate: 9600 $serial->confParity("none"); //Parity (this is the "N" in "8-N-1") $serial->confCharacterLength(8); //Character length (this is the "8" in "8-N-1") $serial->confStopBits(1); //Stop bits (this is the "1" in "8-N-1") // Ask Arduino if the LED is ON or OFF $serial->deviceOpen(); $serial->sendMessage(chr(10)); // start transmission $serial->sendMessage("2"); $serial->sendMessage(chr(13)); // end transmission $read = $serial->readPort(); // waiting for reply $led1 = $read; $led1 = (int)$led1; //We're done, so close the serial port again $serial->deviceClose(); // Add some xhtml and CSS to display an ON/OFF button echo ""; echo ""; echo ""; echo ""; echo "Toggle LED on Arduino"; echo ""; echo ""; echo ""; // if LED is OFF (0), then display the ON button if ($led1 === 0) { echo "

"; } // if LED is ON (1), then display the OFF button if ($led1 === 1) { echo "

"; } echo ""; echo ""; //check the GET action var to see if an action is to be performed if (isset($_GET['action'])) { //Action required //Now we "open" the serial port so we can write to it $serial->deviceOpen(); $serial->sendMessage(chr(10)); // start Transmission //Do the request if ($_GET['action'] == "on") { echo "

"; // toggle the button $serial->sendMessage("1"); // turn LED ON } else if ($_GET['action'] == "off") { echo "

"; // toggle the button $serial->sendMessage("0"); // turn LED OFF } $serial->sendMessage(chr(13)); // end Transmission //We're done, so close the serial port again $serial->deviceClose(); } ?>