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Writing to a Serial Port

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# 8  
Old 10-08-2014
And you run this code by browsing to http://localhost/whatever/myserialscript.php yes?

By doing so, you are instructing your web server to run the script. Your web server probably runs as the apache user and group.
Last edited by Corona688; 10-08-2014 at 01:03 PM..
# 9  
Old 10-08-2014
Where is fclose($fh1); ?
# 10  
Old 10-08-2014
@OP:
Based on the error it seems whoever is trying to run the php script does not have the privileges to do so...can you copy the php snippet and run it on the command line as the user or group member that owns /dev/ttyS0...
# 11  
Old 10-09-2014
Or simply change the permissions on the port to 0666. If you get it to work with that, you can consider what security implications there may be later.
# 12  
Old 10-19-2014
Thanks Shamrock.

".can you copy the php snippet and run it on the command line as the user or group member that owns /dev/ttyS0..."

I'm sorry, I am a newbie. How??

---------- Post updated 10-19-14 at 04:47 PM ---------- Previous update was 10-18-14 at 09:27 PM ----------

Here is some more info -
Code:
root@meow:/dev# ls /dev/ttyS0
/dev/ttyS0
root@meow:/dev# echo test > /dev/ttyS0
root@meow:/dev# ls bla
ls: cannot access bla: No such file or directory
root@meow:/dev# touch bla
root@meow:/dev# ls -l bla
-rw-r--r-- 1 root root 0 Oct 18 22:55 bla
root@meow:/dev# echo test > /dev/ttyS0 >bla
root@meow:/dev# cat bla
test
root@meow:/dev# echo "W\n" > /dev/ttyS0 >bla
root@meow:/dev# cat bla
W\n

Therefore I can write to the port and read from it.
How do I get the output from the scale, which is called by W\n?


TIA
# 13  
Old 10-19-2014
This is not reading from the port. You cannot do 2 redirections. You're attaching stdout to /dev/ttyS0 but immediately changing that to a file called bla.

Code:
mute@thedoctor:~$ echo hi >file1 >file2
mute@thedoctor:~$ ls -l file?
-rw-r--r-- 1 mute mute 0 Oct 19 21:29 file1
-rw-r--r-- 1 mute mute 3 Oct 19 21:29 file2

This shows how redirection to two places fails. You only need to:
Code:
$ echo W >/dev/ttyS0
$ cat /dev/ttyS0

Try to set permissions, as root, to allow everyone access to the serial port with chmod 0666 /dev/ttyS0. If your code then works, the issue is that the webserver doesn't run as ethan, but another user who doesn't have access to ttyS0.
# 14  
Old 10-19-2014
Thanks neutronscott -

This is what I get -
Code:
root@meow:/var/www# ls -l /dev/ttyS0
crw-rw-rw- 1 ethan ethan 4, 64 Oct 18 22:54 /dev/ttyS0
root@meow:/var/www#  echo hi >/dev/ttS0y >bla
root@meow:/var/www# cat bla
hi
root@meow:/var/www# echo W >/dev/ttyS0
root@meow:/var/www# cat /dev/ttyS0  hangs here
^C
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