Perlmonks,

My problem is the following: I have a script that slurps a text file into an array and sends data to a serial port. The data slurped in contains a timecode and data.

The timecode is in milliseconds.

I want to ensure that my data is sent to the serial port at exact times as specified.

Example:
- slurp in file that has the following:
0035020 (first five are timecode, 350ms for this line)
0029024 (last 2 are data to be sent, 24 for this line)
1042201

- send the data "20" over the com port
- wait 350 ms
- send the data "24" over the com port
- wait 290 ms
- send the data "1" over the com port
- wait 10422 ms

the following code shows what I'm doing, but somehow the times are getting off sync...

Is there something I'm overlooking?

use warnings;

use Win32::SerialPort;
use Time::HiRes qw (usleep);

open (CODES, "$ARGV[0]");
my @codes = <CODES>;
close CODES;

my $serial = new Win32::SerialPort ('COM3') or die "Can't open COM3: $
+^E\n";
$serial->databits(8);
$serial->baudrate(9600);
$serial->parity("none");
$serial->stopbits(1);
$serial->write_settings;
my $clearout = $serial->input;
undef $clearout;

my $correctionUs = 13800;   //setting to offset the transfer time of s
+erial communication, not working

print "Hit Enter To Begin";
<STDIN>;

my $starttimeepoch = time;
my $starttime = localtime;
print "Start Time is: $starttime, epoch time is: " . $starttimeepoch .
+ "\n";
print "Correction is: " . $correctionUs . "\n";


foreach my $line (@codes){
 $line =~ /(\d{5})(\d{2})/;
 $serial->write($2);
 usleep(($1 * 1000 )- $correctionUs);
}

my $endtimeepoch = time;
my $endtime = localtime;
print "End Time is: $endtime, epoch time is: " . $endtimeepoch . "\n";
print "Total time is: " . ($endtimeepoch - $starttimeepoch) . "\n";


print "I should be done now, sleeping for 10 seconds\n";
sleep(10);

$serial->close or die "Failed to close COM3";
undef $serial;

[download]

There must be some blocking or something going on, the first hundred or so lines send well, then they get off-sync, then after some time, they'll resync by themselves.

Any ideas?

In reply to Serial Port timing and write blocking? by worldsight

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