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# 1  
Old 10-08-2014
Writing to a Serial Port
I am trying to write to a serial port and capture the reponse in a file -

Code:
adduser ethan dialout 
The user `ethan' is already a member of `dialout'
root@meow:/home/ethan# ls -l /dev/ttyS0
crw-rw-r-- 1 ethan dialout 4, 64 Oct  7 20:55 /dev/ttyS0

$fh1 = fopen("/dev/ttyS0", "w+");
fwrite($fh1, "W\n"); //This sends a signal to a scale to return the weight of an object
fread($fh1, 100);
echo $fh1;

If I run this code -


Warning: fopen(/dev/ttyS0): failed to open stream: Permission denied in /var/www/TestScale.php on line 20

Warning: fwrite() expects parameter 1 to be resource, boolean given in /var/www/TestScale.php on line 21

Warning: fread() expects parameter 1 to be resource, boolean given in /var/www/TestScale.php on line 22

TIA
# 2  
Old 10-08-2014
Are you running that php script as root user...and post the output of setserial -a /dev/ttyS0 here...
# 3  
Old 10-08-2014
Thanks shamrock.
Running as user.

How would I run a PHP script as root?
TIA
Code:
root@meow:/home/ethan# setserial -a /dev/ttyS0 
/dev/ttyS0, Line 0, UART: 16550A, Port: 0x03f8, IRQ: 4
    Baud_base: 115200, close_delay: 50, divisor: 0
    closing_wait: 3000
    Flags: spd_normal skip_test

# 4  
Old 10-08-2014
Perhaps if you walk before running we might be able to solve your problem(s) as you have asked a near identical question here:-

Reading data from a serial port
# 5  
Old 10-08-2014
Thanks wisecracker -

Correct.

That thread was in the Debian forum.

This question here is in PHP programming and I thought, mistakenly, that this question belonged here. I do not think threads are identical. If an apology is needed, I apologize.
# 6  
Old 10-08-2014
I do not think the question is identical. Related, but PHP & CGI have their own issues. Still not quite the right forum, but I can fix that. No harm done.

If you are running it from PHP, you are probably running it from CGI, yes? User accesses a webpage via HTTP and your script runs -- but as "apache", not as you.
# 7  
Old 10-08-2014
Thanks Corona688.

I'm not sure that I understand you.

Here is the code -

PHP Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

<html>

    <head>
        <title>Test Scale</title>
    </head>
        <body>
        <strong>
            <div align='center'>
                  <h3>Test Scale</h3>
            </strong>
                    </div>

<?php
            error_reporting(E_ALL | E_NOTICE);
            ini_set('display_errors','1');
            
            $fh1 = fopen("/dev/ttyS0", "w+");
            fwrite($fh1, "W\n");
            fread($fh1, 100);
            echo $fh1;

?>

        </body>
</html>
When I can get this to run, I'll add a form which will call the code.

TIA
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