Send command to SerialPort and read answer: PERL, SerialPort, Windows XP

by: Adam314Posted on 2009-04-29 at 10:27:02ID: 24262686

Use the read and write methods...

From the documentation:

#Find how many bytes are waiting (and some other stuff)
($BlockingFlags, $InBytes, $OutBytes, $LatchErrorFlags) = $PortObj->status
  || warn "could not get port status\n";
 
#Read bytes, give warning if error
($count_in, $string_in) = $PortObj->read($InBytes);
warn "read unsuccessful\n" unless ($count_in == $InBytes);
#Now, $string_in contains the now bytes
 
 
#Write bytes, give warning if error
$count_out = $PortObj->write($output_string);
warn "write failed\n"         unless ($count_out);
warn "write incomplete\n"     if ( $count_out != length($output_string) );

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by: TheFlyingCorpsePosted on 2009-04-29 at 15:28:27ID: 24265354

so if I want to use the following 2 commands, how would I then execute them in the script?
(I've only written scripts for local checking and webchecking before, never touched SerialPort in any form)
1st command: AT
2nd command: AT!TEST?

I want do use the output of the 2nd command in code I already have, as long as I can get it from a file or variable from this part.

by: Adam314Posted on 2009-04-30 at 08:31:34ID: 24271028

#Create $PortObj, and set it's properties here
 
#Send first command
my $StrToSend = 'AT';
my $count_out = $PortObj->write($StrToSend);
die "Tried to write ".length($StrToSend)." bytes, but wrote $count_out bytes\n"
  unless ($count_out and ($count_out == length($StrToSend));
 
#Do you need to check that the command was successful?
#If so, do that here.  I thought you should get an "OK" response back.
 
$StrToSend='AT!TEST?';
$count_out = $PortObj->write($StrToSend);
die "Tried to write ".length($StrToSend)." bytes, but wrote $count_out bytes\n"
  unless ($count_out and ($count_out == length($StrToSend));
 
#Find how many bytes are waiting (and some other stuff)
($BlockingFlags, $InBytes, $OutBytes, $LatchErrorFlags) = $PortObj->status
  || die "could not get port status\n";
 
#Read bytes, give warning if error
($count_in, $string_in) = $PortObj->read($InBytes);
die "read unsuccessful\n" unless ($count_in == $InBytes);
 
#You can now use $string_in

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by: TheFlyingCorpsePosted on 2009-04-30 at 18:52:07ID: 24276176

How does this look as a solution?

I added the part with use Win32::SerialPort, what port and also an attempt to verify that the AT command recieves an OK before issuing the AT!TEST?

I have yet to test it on the computer that is to use it. (didnt bring it home from work), will drop by work tomorrow even though its a global holiday ;)

#Create $PortObj, and set it's properties here
 
use Win32::SerialPort
 
$PortName = "COM1";
 
$PortObj = new Win32::SerialPort ($PortName) 
     || die "Can't open $Portname: $^E\n";
 
#Send first command
my $StrToSend = 'AT';
my $count_out = $PortObj->write($StrToSend);
die "Tried to write ".length($StrToSend)." bytes, but wrote $count_out bytes\n"
  unless ($count_out and ($count_out == length ($StrToSend));
 
#Find how many bytes are waiting (and some other stuff)
($BlockingFlags, $InBytes, $OutBytes, $LatchErrorFlags) = $PortObj->status
  || die "could not get port status\n";
 
#Read bytes, give warning if error
($count_in, $string_in) = $PortObj->read($InBytes);
die "read unsuccessful\n" unless ($count_in == $InBytes);
if ($string_in = 'OK') {
 
#Send command for test 
$StrToSend='AT!TEST?';
$count_out = $PortObj->write($StrToSend);
die "Tried to write ".length($StrToSend)." bytes, but wrote $count_out bytes\n"
  unless ($count_out and ($count_out == length ($StrToSend));
 
#Find how many bytes are waiting (and some other stuff)
($BlockingFlags, $InBytes, $OutBytes, $LatchErrorFlags) = $PortObj->status
  || die "could not get port status\n";
 
#Read bytes, give warning if error
($count_in, $string_in) = $PortObj->read($InBytes);
die "read unsuccessful\n" unless ($count_in == $InBytes);
 } else {
print "Failed to communicate with the COM-port\n";
}
#You can now use $string_in

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by: Adam314Posted on 2009-05-01 at 10:03:10ID: 24281345

It looks okay to me.

by: TheFlyingCorpsePosted on 2009-05-01 at 11:43:19ID: 24282285

ok, thanks :-)

Btw, i am unable to compile Win32::Serialport.
I get an error with it that it cannot find the html base directory, even though I've added it to the makefile.
I've tried it both on the computer in question and in a VMware instance.
I use the Strawberry-perl distro, also tried with the ActivePerl but havent got as far with that since there is no Win32::SerialPort already compiled for it.

I can open a different question for it if you want me to, but it would be really nice if I could get it to work!

by: Adam314Posted on 2009-05-01 at 11:58:35ID: 24282423

Looks like it is available here for ActiveState already compiled:
http://www.bribes.org/perl/ppm/Win32-SerialPort.ppd

I'm not sure of the problem with the strawberry when you compile. You you have permission to write to the html directory? Does it tell you what directory it expect for the html base directory? Is it relative, or absolute?

by: TheFlyingCorpsePosted on 2009-05-01 at 13:19:39ID: 31576030

The expert was able to give a proper and very usable solution to my question, with a good understanding of the solution.

by: TheFlyingCorpsePosted on 2009-05-01 at 13:20:36ID: 24283078

I added the bribes repo, that solved the issue with the Win32::SerialPort.

It works now, thank you!

by: JCaturiaPosted on 2009-07-28 at 10:52:13ID: 24963119

Did you notice that in line #23 of your code above you are not doing a comparison, but an assignment?

if ($string_in = 'OK') {

This will _never_ fail - which defeats your purpose I'm sure.. :) Just thought you should know! You may have already fixed it, since the thread is so old.

Question

Send command to SerialPort and read answer

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PERL

SerialPort

Windows XP

Perl Programming Language

Windows XP Operating System

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