CyborgHamster Posted October 22, 2013 Share Posted October 22, 2013 Hello, I am using php to write to Arduino via a serial port (/dev/ttyACM0). The problem that I ran into is that I keep getting an Access Denied error in the log for the port. If I chmod the port, I can then write to it, but that only lasts until I make a change to the Arduino code or reset the device or computer. I tried adding myself to the dialout group and the uucp group like some sites suggested, but I still can not write to the port unless I chmod it first. I can also write to the port using python without any errors. Is their a way to force php to always allow me to write to that port? Here is the php code <?php $verz="1.0"; $comPort = "/dev/ttyACM0"; /*change to correct com port */ if (isset($_POST["rcmd"])) { $rcmd = $_POST["rcmd"]; switch ($rcmd) { case "ON": $fp = fopen($comPort, "w") or die("Can't Open Port"); fwrite($fp, "1"); sleep(1); fclose($fp); break; case "OFF": $fp = fopen($comPort, "w"); fwrite($fp, "0"); sleep(1); fclose($fp); break; } } ?> <html> <body> <center><h1>Arduino from PHP Example</h1><b>Version <?php echo $verz; ?></b></center> <form method="post" action="index.php"> <input type="submit" value="ON" name="rcmd"> <input type="submit" value="OFF" name="rcmd"> </form> </body> </html> and here is the error [Tue Oct 22 14:19:10 2013] [error] [client 127.0.0.1] PHP Warning: fopen(/dev/ttyACM0): failed to open stream: Permission denied in /var/www/arduino/index.php on line 10, referer: http://127.0.0.1/arduino/index.php Any help would be appreciated, Thanks Link to comment https://forums.phpfreaks.com/topic/283198-php-fopen-serial-port-access-denied/ Share on other sites More sharing options...
kicken Posted October 22, 2013 Share Posted October 22, 2013 What are the permissions and owner/group for /dev/ttyACM0? What groups are you a member of? Can you run the necessary chmod with PHP before opening the file? Note that if you are running this via apache which your error message indicates, you need to consider the user that apache is executing the script as, not what your login user is when determining the permissions and groups. For example, you'd need to add apache's user to the dialup / uucp groups, not yourself. Link to comment https://forums.phpfreaks.com/topic/283198-php-fopen-serial-port-access-denied/#findComment-1454998 Share on other sites More sharing options...
CyborgHamster Posted October 22, 2013 Author Share Posted October 22, 2013 kicken Note that if you are running this via apache which your error message indicates, you need to consider the user that apache is executing the script as, not what your login user is when determining the permissions and groups. For example, you'd need to add apache's user to the dialup / uucp groups, not yourself. THANK YOU!!!! It was so simple but I over looked it. I had tried adding the user apache to the group but was getting a user error. Then I ran ps aux | egrep '(apache|httpd)' which showed me that the user was www-data. Then I added www-data to the group dialout using sudo usermod -a -G dialout www-data and after I logged out and back in it works! Link to comment https://forums.phpfreaks.com/topic/283198-php-fopen-serial-port-access-denied/#findComment-1455014 Share on other sites More sharing options...
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