Heisann.. Noen som kan hjelpe meg med å forstå hvordan selve utregningen i dette Perl-scriptet foregår?
For eksempel har man kommet frem til at denne selve teksten i denne linjen her har generert checksumen 4B.
sub toled {
my $page = shift;
my $str = shift;
# calculate checksum
my $checksum = 0x74;
for (0..length($str)-1) {
my $c = ord(substr($str,$_));
$checksum = $checksum ^ $c;
}
# construct basic "display this on page $page" message
my $ledcode = sprintf("<ID00><L1><P%s><FE><MA><WC><FE>%s%02X<E>",
uc($page), $str, $checksum);
# send to serial device /dev/ttyS0
open SERIAL, ">/dev/ttyS0";
print SERIAL $ledcode;
close SERIAL;
}
my $page = shift;
my $str = shift;
# calculate checksum
my $checksum = 0x74;
for (0..length($str)-1) {
my $c = ord(substr($str,$_));
$checksum = $checksum ^ $c;
}
# construct basic "display this on page $page" message
my $ledcode = sprintf("<ID00><L1><P%s><FE><MA><WC><FE>%s%02X<E>",
uc($page), $str, $checksum);
# send to serial device /dev/ttyS0
open SERIAL, ">/dev/ttyS0";
print SERIAL $ledcode;
close SERIAL;
}
Vis hele sitatet...
<ID00><L1><PA><FE><MA><WC><FE>Text message entered4B<E>
Vis hele sitatet...
