PHP Ajax Serial Port String Command

Question

I"m very new to PHP and AJAX and have been learning some of the basics over the last few weeks. I've used quite a few posts on this site for help along the way and when my current problem came up I figured this would be a good place to start.

What I'm trying to do is pass a hexidecimal command string to PHP to be output using the serial port of my device. The problem i'm seeing is that the string that i'm passing to the PHP for some reason is adding a hex character in the middle of it. At first I thought this had something to do with special characters defined in the serial port but when I define the string within the PHP code I don't get the same error. I've also noticed that the additional character is added before any character in my string that has \xA# in it where # could be any number 0-9.

Basically i'm trying to send the hex command string \x55\x05\xA0\x05\x05 to php using ajax to be output on a serial port. When I execute the command I see the following on the serial port. U0x050xc20xa0x050x05 Somewhere along the way the "0xc2" is being added to the serial output. As mentioned previously it seems to be related to \xAO because when I replace that with \x04 making the string \x55\x05\x04\x05\x05 I get the correct output of u0x050x040x050x05. This issue also occurs when I use \A1 I also get the same error.

When I define the string in the PHP file I get the correct output of U0x050xa0x050x05

Any idea what is causing this? Should I be sending the hex commands as an array instead of a string and putput them one at a time over the serial port?

Here is my code with the javascript and ajax call. Basically when I press a button I want to send a specific hex command string to the PHP function and output it over the serial port.

<!doctype html>
<html lang="en">
<head>
    <meta charset="utf-8" />
    <title>Button Test</title>

    <!-- CSS for presentation. -->
    <style>
    h1 { font-size: 20px; color: red; }
    button { color: black; }
    </style>
<script src="jquery.js">
</script>
<script>
function sercmd( stringcmd )
{
//Calling ajax and including the serial command to be sent out the serial port
//$.ajax({url: "sendserial.php", type: "POST", data: {serstr: stringcmd}, dataType: "json"});
$.ajax({
    url: "sendserial.php",
    type: "POST",
    data: {serstr: stringcmd},
    success: function ( resp ){
        if ( resp == 'true'){
            $( '.response' ).text( resp );
        } else {
            $( '.response' ).text( 'failure' );
        }
    }
});
}
</script>
</head>
<body>

    <h1>Test Page for MZC Control</h1>


    <button onclick="sercmd('\x55\x05\xA0\x05\x05') ">Zone 3 Power On</button>
    <button onclick="sercmd('\x55\x04\xA1\x02\x04') ">Zone 3 Power Off</button>
    <button onclick="sercmd('\x55\x05\xA3\x02\x00\x01') ">Zone 3 Source 1</button>
    <button onclick="sercmd('\x55\x05\xA3\x02\x01\x00') ">Zone 3 Source 2</button>


    <p> Control The Zones using the commands above. </p>   
<div class="response"></div>

</body>
</html>

Here is the code from the PHP page being called by AJAX

<?php
error_reporting(E_ALL);
ini_set('display_errors', '1');
include "php_serial.class.php";

$str = $_POST['serstr'];

//$str = '\x55\x04\xA0\x02\x05';

//$str = pack("H*",$str);

$serial = new phpSerial;
$serial->deviceSet("/dev/ttyUSB0");
$serial->confBaudRate(57600);
$serial->confParity("none");
$serial->confCharacterLength(8);
$serial->confStopBits(1);
$serial->confFlowControl("none");

$serial->deviceOpen();

$serial->sendMessage($str);

//$serial->sendMessage("\x55");

//$read = $serial->readPort();

$serial->deviceClose();

echo $str;
//echo "true";
//echo $read;
?>

Just in case someone is interested here is the code for the php serial class that i'm using. I found this being used by others in this forum.

<?php
define ("SERIAL_DEVICE_NOTSET", 0);
define ("SERIAL_DEVICE_SET", 1);
define ("SERIAL_DEVICE_OPENED", 2);

/**
 * Serial port control class
 *
 * THIS PROGRAM COMES WITH ABSOLUTELY NO WARANTIES !
 * USE IT AT YOUR OWN RISKS !
 *
 * @author Rémy Sanchez <thenux@gmail.com>
 * @thanks Aurélien Derouineau for finding how to open serial ports with windows
 * @thanks Alec Avedisyan for help and testing with reading
 * @copyright under GPL 2 licence
 */
class phpSerial
{
    var $_device = null;
    var $_windevice = null;
    var $_dHandle = null;
    var $_dState = SERIAL_DEVICE_NOTSET;
    var $_buffer = "";
    var $_os = "";

    /**
     * This var says if buffer should be flushed by sendMessage (true) or manualy (false)
     *
     * @var bool
     */
    var $autoflush = true;

    /**
     * Constructor. Perform some checks about the OS and setserial
     *
     * @return phpSerial
     */
    function phpSerial ()
    {
        setlocale(LC_ALL, "en_US");

        $sysname = php_uname();

        if (substr($sysname, 0, 5) === "Linux")
        {
            $this->_os = "linux";

            if($this->_exec("stty --version") === 0)
            {
                register_shutdown_function(array($this, "deviceClose"));
            }
            else
            {
                trigger_error("No stty availible, unable to run.", E_USER_ERROR);
            }
        }
        elseif(substr($sysname, 0, 7) === "Windows")
        {
            $this->_os = "windows";
            register_shutdown_function(array($this, "deviceClose"));
        }
        else
        {
            trigger_error("Host OS is neither linux nor windows, unable tu run.", E_USER_ERROR);
            exit();
        }
    }

    //
    // OPEN/CLOSE DEVICE SECTION -- {START}
    //

    /**
     * Device set function : used to set the device name/address.
     * -> linux : use the device address, like /dev/ttyS0
     * -> windows : use the COMxx device name, like COM1 (can also be used
     *     with linux)
     *
     * @param string $device the name of the device to be used
     * @return bool
     */
    function deviceSet ($device)
    {
        if ($this->_dState !== SERIAL_DEVICE_OPENED)
        {
            if ($this->_os === "linux")
            {
                if (preg_match("@^COM(\d+):?$@i", $device, $matches))
                {
                    $device = "/dev/ttyS" . ($matches[1] - 1);
                }

                if ($this->_exec("stty -F " . $device) === 0)
                {
                    $this->_device = $device;
                    $this->_dState = SERIAL_DEVICE_SET;
                    return true;
                }
            }
            elseif ($this->_os === "windows")
            {
                if (preg_match("@^COM(\d+):?$@i", $device, $matches) and $this->_exec(exec("mode " . $device)) === 0)
                {
                    $this->_windevice = "COM" . $matches[1];
                    $this->_device = "\\.\com" . $matches[1];
                    $this->_dState = SERIAL_DEVICE_SET;
                    return true;
                }
            }

            trigger_error("Specified serial port is not valid", E_USER_WARNING);
            return false;
        }
        else
        {
            trigger_error("You must close your device before to set an other one", E_USER_WARNING);
            return false;
        }
    }

    /**
     * Opens the device for reading and/or writing.
     *
     * @param string $mode Opening mode : same parameter as fopen()
     * @return bool
     */
    function deviceOpen ($mode = "r+b")
    {
        if ($this->_dState === SERIAL_DEVICE_OPENED)
        {
            trigger_error("The device is already opened", E_USER_NOTICE);
            return true;
        }

        if ($this->_dState === SERIAL_DEVICE_NOTSET)
        {
            trigger_error("The device must be set before to be open", E_USER_WARNING);
            return false;
        }

        if (!preg_match("@^[raw]\+?b?$@", $mode))
        {
            trigger_error("Invalid opening mode : ".$mode.". Use fopen() modes.", E_USER_WARNING);
            return false;
        }

        $this->_dHandle = @fopen($this->_device, $mode);

        if ($this->_dHandle !== false)
        {
            stream_set_blocking($this->_dHandle, 0);
            $this->_dState = SERIAL_DEVICE_OPENED;
            return true;
        }

        $this->_dHandle = null;
        trigger_error("Unable to open the device", E_USER_WARNING);
        return false;
    }

    /**
     * Closes the device
     *
     * @return bool
     */
    function deviceClose ()
    {
        if ($this->_dState !== SERIAL_DEVICE_OPENED)
        {
            return true;
        }

        if (fclose($this->_dHandle))
        {
            $this->_dHandle = null;
            $this->_dState = SERIAL_DEVICE_SET;
            return true;
        }

        trigger_error("Unable to close the device", E_USER_ERROR);
        return false;
    }

    //
    // OPEN/CLOSE DEVICE SECTION -- {STOP}
    //

    //
    // CONFIGURE SECTION -- {START}
    //

    /**
     * Configure the Baud Rate
     * Possible rates : 110, 150, 300, 600, 1200, 2400, 4800, 9600, 38400,
     * 57600 and 115200.
     *
     * @param int $rate the rate to set the port in
     * @return bool
     */
    function confBaudRate ($rate)
    {
        if ($this->_dState !== SERIAL_DEVICE_SET)
        {
            trigger_error("Unable to set the baud rate : the device is either not set or opened", E_USER_WARNING);
            return false;
        }

        $validBauds = array (
            110    => 11,
            150    => 15,
            300    => 30,
            600    => 60,
            1200   => 12,
            2400   => 24,
            4800   => 48,
            9600   => 96,
            19200  => 19,
            38400  => 38400,
            57600  => 57600,
            115200 => 115200
        );

        if (isset($validBauds[$rate]))
        {
            if ($this->_os === "linux")
            {
                $ret = $this->_exec("stty -F " . $this->_device . " " . (int) $rate, $out);
            }
            elseif ($this->_os === "windows")
            {
                $ret = $this->_exec("mode " . $this->_windevice . " BAUD=" . $validBauds[$rate], $out);
            }
            else return false;

            if ($ret !== 0)
            {
                trigger_error ("Unable to set baud rate: " . $out[1], E_USER_WARNING);
                return false;
            }
        }
    }

    /**
     * Configure parity.
     * Modes : odd, even, none
     *
     * @param string $parity one of the modes
     * @return bool
     */
    function confParity ($parity)
    {
        if ($this->_dState !== SERIAL_DEVICE_SET)
        {
            trigger_error("Unable to set parity : the device is either not set or opened", E_USER_WARNING);
            return false;
        }

        $args = array(
            "none" => "-parenb",
            "odd"  => "parenb parodd",
            "even" => "parenb -parodd",
        );

        if (!isset($args[$parity]))
        {
            trigger_error("Parity mode not supported", E_USER_WARNING);
            return false;
        }

        if ($this->_os === "linux")
        {
            $ret = $this->_exec("stty -F " . $this->_device . " " . $args[$parity], $out);
        }
        else
        {
            $ret = $this->_exec("mode " . $this->_windevice . " PARITY=" . $parity{0}, $out);
        }

        if ($ret === 0)
        {
            return true;
        }

        trigger_error("Unable to set parity : " . $out[1], E_USER_WARNING);
        return false;
    }

    /**
     * Sets the length of a character.
     *
     * @param int $int length of a character (5 <= length <= 8)
     * @return bool
     */
    function confCharacterLength ($int)
    {
        if ($this->_dState !== SERIAL_DEVICE_SET)
        {
            trigger_error("Unable to set length of a character : the device is either not set or opened", E_USER_WARNING);
            return false;
        }

        $int = (int) $int;
        if ($int < 5) $int = 5;
        elseif ($int > 8) $int = 8;

        if ($this->_os === "linux")
        {
            $ret = $this->_exec("stty -F " . $this->_device . " cs" . $int, $out);
        }
        else
        {
            $ret = $this->_exec("mode " . $this->_windevice . " DATA=" . $int, $out);
        }

        if ($ret === 0)
        {
            return true;
        }

        trigger_error("Unable to set character length : " .$out[1], E_USER_WARNING);
        return false;
    }

    /**
     * Sets the length of stop bits.
     *
     * @param float $length the length of a stop bit. It must be either 1,
     * 1.5 or 2. 1.5 is not supported under linux and on some computers.
     * @return bool
     */
    function confStopBits ($length)
    {
        if ($this->_dState !== SERIAL_DEVICE_SET)
        {
            trigger_error("Unable to set the length of a stop bit : the device is either not set or opened", E_USER_WARNING);
            return false;
        }

        if ($length != 1 and $length != 2 and $length != 1.5 and !($length == 1.5 and $this->_os === "linux"))
        {
            trigger_error("Specified stop bit length is invalid", E_USER_WARNING);
            return false;
        }

        if ($this->_os === "linux")
        {
            $ret = $this->_exec("stty -F " . $this->_device . " " . (($length == 1) ? "-" : "") . "cstopb", $out);
        }
        else
        {
            $ret = $this->_exec("mode " . $this->_windevice . " STOP=" . $length, $out);
        }

        if ($ret === 0)
        {
            return true;
        }

        trigger_error("Unable to set stop bit length : " . $out[1], E_USER_WARNING);
        return false;
    }

    /**
     * Configures the flow control
     *
     * @param string $mode Set the flow control mode. Availible modes :
     *  -> "none" : no flow control
     *  -> "rts/cts" : use RTS/CTS handshaking
     *  -> "xon/xoff" : use XON/XOFF protocol
     * @return bool
     */
    function confFlowControl ($mode)
    {
        if ($this->_dState !== SERIAL_DEVICE_SET)
        {
            trigger_error("Unable to set flow control mode : the device is either not set or opened", E_USER_WARNING);
            return false;
        }

        $linuxModes = array(
            "none"     => "clocal -crtscts -ixon -ixoff",
            "rts/cts"  => "-clocal crtscts -ixon -ixoff",
            "xon/xoff" => "-clocal -crtscts ixon ixoff"
        );
        $windowsModes = array(
            "none"     => "xon=off octs=off rts=on",
            "rts/cts"  => "xon=off octs=on rts=hs",
            "xon/xoff" => "xon=on octs=off rts=on",
        );

        if ($mode !== "none" and $mode !== "rts/cts" and $mode !== "xon/xoff") {
            trigger_error("Invalid flow control mode specified", E_USER_ERROR);
            return false;
        }

        if ($this->_os === "linux")
            $ret = $this->_exec("stty -F " . $this->_device . " " . $linuxModes[$mode], $out);
        else
            $ret = $this->_exec("mode " . $this->_windevice . " " . $windowsModes[$mode], $out);

        if ($ret === 0) return true;
        else {
            trigger_error("Unable to set flow control : " . $out[1], E_USER_ERROR);
            return false;
        }
    }

    /**
     * Sets a setserial parameter (cf man setserial)
     * NO MORE USEFUL !
     *  -> No longer supported
     *  -> Only use it if you need it
     *
     * @param string $param parameter name
     * @param string $arg parameter value
     * @return bool
     */
    function setSetserialFlag ($param, $arg = "")
    {
        if (!$this->_ckOpened()) return false;

        $return = exec ("setserial " . $this->_device . " " . $param . " " . $arg . " 2>&1");

        if ($return{0} === "I")
        {
            trigger_error("setserial: Invalid flag", E_USER_WARNING);
            return false;
        }
        elseif ($return{0} === "/")
        {
            trigger_error("setserial: Error with device file", E_USER_WARNING);
            return false;
        }
        else
        {
            return true;
        }
    }

    //
    // CONFIGURE SECTION -- {STOP}
    //

    //
    // I/O SECTION -- {START}
    //

    /**
     * Sends a string to the device
     *
     * @param string $str string to be sent to the device
     * @param float $waitForReply time to wait for the reply (in seconds)
     */
    function sendMessage ($str, $waitForReply = 0.1)
    {
        $this->_buffer .= $str;

        if ($this->autoflush === true) $this->flush();

        usleep((int) ($waitForReply * 1000000));
    }

    /**
     * Reads the port until no new datas are availible, then return the content.
     *
     * @pararm int $count number of characters to be read (will stop before
     *  if less characters are in the buffer)
     * @return string
     */
    function readPort ($count = 0)
    {
        if ($this->_dState !== SERIAL_DEVICE_OPENED)
        {
            trigger_error("Device must be opened to read it", E_USER_WARNING);
            return false;
        }

        if ($this->_os === "linux")
        {
            $content = ""; $i = 0;

            if ($count !== 0)
            {
                do {
                    if ($i > $count) $content .= fread($this->_dHandle, ($count - $i));
                    else $content .= fread($this->_dHandle, 128);
                } while (($i += 128) === strlen($content));
            }
            else
            {
                do {
                    $content .= fread($this->_dHandle, 128);
                } while (($i += 128) === strlen($content));
            }

            return $content;
        }
        elseif ($this->_os === "windows")
        {
            /* Do nohting : not implented yet */
        }

        trigger_error("Reading serial port is not implemented for Windows", E_USER_WARNING);
        return false;
    }

    /**
     * Flushes the output buffer
     *
     * @return bool
     */
    function flush ()
    {
        if (!$this->_ckOpened()) return false;

        if (fwrite($this->_dHandle, $this->_buffer) !== false)
        {
            $this->_buffer = "";
            return true;
        }
        else
        {
            $this->_buffer = "";
            trigger_error("Error while sending message", E_USER_WARNING);
            return false;
        }
    }

    //
    // I/O SECTION -- {STOP}
    //

    //
    // INTERNAL TOOLKIT -- {START}
    //

    function _ckOpened()
    {
        if ($this->_dState !== SERIAL_DEVICE_OPENED)
        {
            trigger_error("Device must be opened", E_USER_WARNING);
            return false;
        }

        return true;
    }

    function _ckClosed()
    {
        if ($this->_dState !== SERIAL_DEVICE_CLOSED)
        {
            trigger_error("Device must be closed", E_USER_WARNING);
            return false;
        }

        return true;
    }

    function _exec($cmd, &$out = null)
    {
        $desc = array(
            1 => array("pipe", "w"),
            2 => array("pipe", "w")
        );

        $proc = proc_open($cmd, $desc, $pipes);

        $ret = stream_get_contents($pipes[1]);
        $err = stream_get_contents($pipes[2]);

        fclose($pipes[1]);
        fclose($pipes[2]);

        $retVal = proc_close($proc);

        if (func_num_args() == 2) $out = array($ret, $err);
        return $retVal;
    }

    //
    // INTERNAL TOOLKIT -- {STOP}
    //
}
?>

`$serial->confCharacterLength(8);` perhaps ? your input string is longer than 8 so its truncating it and effectively sending it as 2 commands down the one open port so its putting in headers/spacings in the string. — Dave, Jan 22 '14 at 15:00

score 0 · Accepted Answer · edited May 23 '17 at 11:56

0

Possible solutions

Convert hex to string, and string to hex

Convert hex to string, and send. Then, back to hex.

Using this functions:

<?php
function strToHex($string){
    $hex = '';
    for ($i=0; $i<strlen($string); $i++){
        $ord = ord($string[$i]);
        $hexCode = dechex($ord);
        $hex .= substr('0'.$hexCode, -2);
    }
    return strToUpper($hex);
}
function hexToStr($hex){
    $string='';
    for ($i=0; $i < strlen($hex)-1; $i+=2){
        $string .= chr(hexdec($hex[$i].$hex[$i+1]));
    }
    return $string;
}

Page charset

Check charset of your primary and secondary pages

References

edited May 23 '17 at 11:56

Community

1
1

answered Jan 22 '14 at 15:11

Patrick Maciel

4,874
8
40
80

I did as you suggested and converted the hex command string I wanted to send to its decimal equivalent and sent that to the PHP using the ajax call. With in the PHP i convert the dec string to a hex string and send the result and it worked as desired. It would be much easier if I didn't have to do this conversion for every command I want to send but atleast it works. I'm thinking you also might be on to something with checking the charset. Sounds like my original issue may be a result of an encoding mismatch. thanks for the input. – user3223822 Jan 23 '14 at 19:26
@user3223822 I'm glad to help. The possible problems are enconding or header type (plain text or utf-8), you need to try that checking every page. Tip: try set the charset to UTF-8, and sent a command without convert... next time, try convert to ISO-8859-1 or Plain Text. If have differences.. done! – Patrick Maciel Jan 23 '14 at 19:33
@user3223822 Do not forget to mark my answer as solved if it was the expected answer for you. – Patrick Maciel Jan 23 '14 at 19:35
Its definitely an encoding issue and its related to UTF-8. Based on some reading for hex values above x7F, UTF-8 requires two bytes to encode them adding the "xC2" as the first byte. I've defined the encoding in my javascript/ajax page as UTF-8 but have not clearly defined it in the PHP that reads the string from the AJAX call. Do you think its as simple as defining the encoding on the PHP that reads the string as UTF-8 using mb_internal_encoding("UTF-8");? Or would you suggest changing the encoding on the page where the string originates to something? – user3223822 Jan 23 '14 at 21:20
@user3223822 I suggest you do all operations using the same encoding, in other words: change charset of all files to UTF-8. – Patrick Maciel Jan 23 '14 at 21:25
I ensured that all pages/files were set to UTF-8 encoding but that did not clear up my issues. However I did find a function to decode UTF-8 which worked. $str = utf8_decode($str); This command changed the 2 byte UTF-8 encoded characters back to 1 byte characters. – user3223822 Jan 24 '14 at 14:52
@user3223822 now, we have a complicated situation. If charset not solve your problem.. we need to search about hex values with charsets... I'll try found a solution for that. – Patrick Maciel Jan 24 '14 at 15:03
My problem has been solved with the UTF-8 decode function. I believe the problem is that the command string is encoded to UTF-8 and sent to the PHP server which reads it fine but still sees it as encoded in UTF-8. The problem was actually that my receiving device does not support UTF-8 encoding thus I needed to decode the string back to the original hex string. Thanks for the help. the only issue left is that the receiving device has a communications window that the command must be sent within. The receiving device sends 0x11 when the window is opened. I asked a new question for this one. – user3223822 Jan 24 '14 at 15:12

score 0 · Answer 2 · answered Jul 27 '14 at 00:59

// i try this code and it works well with me
 <meta charset="UTF-8"/>
    <?PHP
     exec("mode COM6: BAUD=9600 PARITY=n DATA=8 STOP=1 to=off dtr=off rts=off");
     echo ord(97);
     $fp =fopen("COM6", "r+");
     fwrite($fp,'b');
     fclose($fp);
   ?>

PHP Ajax Serial Port String Command

2 Answers2

Possible solutions

Convert hex to string, and string to hex

Page charset

References