I needed to talk to two serial port devices, one I had working some time ago on Linux, and the other I got working within 10 minutes on Linux, but porting to windows proved to be quite hard. I got ActivePerl, installed Win32::Serial using the package manager: 
ppm install Win32::SerialPoint
ppm install Win32::API

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the code that works on Linux opens a file handle and uses stty to set the baud rate: 
use strict;
my $deckbox = "/dev/ttyUSB0";
open(DECK, "+<$deckbox") || die('Couldn\'t open GPS');
system("stty -F $deckbox 19200");
while (my $line = <DECK>) {
  print $line;
  print DECK "\$CCPDT,1,4,0,0,3000,1,0,0,0\r\n";
}

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Elegant and simple, right? On windows, there is no stty, so barring installing cygwin, which I would rather not have to do, I had to use the Win32::Serial package. It works fine for a GPS, but for this device, inexplicably no. Perhaps its one of many parameters of the serial port, so I will paste in the output to stty -a -F/dev/ttyUSB0 on linux: 
stty -a -F /dev/ttyUSB0
speed 19200 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; 
+eol2 = <undef>; start = ^Q;
stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O;
+ min = 1; time = 0;
-parenb -parodd cs8 hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixo
+n -ixoff -iuclc -ixany -imaxbel
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs
+0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -ec
+hoprt echoctl echoke

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The windows code that gives back gibberish: 
require 5.003;
use Win32::SerialPort qw( :STAT 0.19 );
use strict;
my $line;
my $deck = openSerial("com3:", 19200, 'none', 8, 1);
# $deck->handshake("xon");
# $deck->buffers(4096,4096);

do {
    my $bytesWritten =
$deck->write('$CCPDT,1,4,0,0,3000,1,0,0,0' . "\r\n");
    $line = rawReadSerial($deck);
} while (1);

sub readLineSerial {
  my ($ser) = @_;
  my ($numChars, $c);
  my $line = '';
  do {
    do {
      ($numChars, $c) = $ser->read(1);
    } while ($numChars < 1);
      $line .= $c;
  } while ($c ne "\n");
  return $line;
}

sub rawReadSerial {
  my ($ser) = @_;
  my ($numChars, $c);
  my $line = '';
  do {
    do {
      ($numChars, $c) = $ser->read(1);
      #print "$numChars read=$c\n";
    } while ($numChars < 1);
     print $c;
    $line .= $c;
  } while ($c ne "\n");
  return $line;
}

[download]
Can anyone tell me what I'm missing?

In reply to serial port control on Windows by hydrodog

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