sub FT_OpenPM{
   my ( $self, $devNum ) = @_;
   my $status = $self->{'FT_STATUS'};
   my $handle = $self->{'FT_HANDLE'};
   #import function
   my $fct_open = new Win32::API( 'FTD2XX', 'FT_Open', 'IP', 'I' );
   unless( $fct_open ){
       print("FT_Open not found!\n");
       return 0;
   }
   #call imported function
   $status = $fct_open->Call( $devNum, $handle );
   print "[$handle]\n";
   $handle =~ s/\0.*$//;
   print "[$handle]\n";
   #$handle = Storable::retrieve( $handle );
   #return the functions return status and the handle
   return ($status, $handle);