I guess you need to send a byte value. See chr, or pack("C",...) (for values 0..255): 

$ob->write(chr($x*10));
# or
$ob->write(pack("C", $x*10));

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In reply to Re: Casting magic - how to write numbers to the serial port by almut
in thread Casting magic - how to write numbers to the serial port by ehud42

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