read length and header (3 bytes) until done

diff --git a/lib/RFID/Serial/3M810.pm b/lib/RFID/Serial/3M810.pm
index 41fd380..892c20f 100644 (file)
--- a/lib/RFID/Serial/3M810.pm
+++ b/lib/RFID/Serial/3M810.pm
@@ -62,9 +62,9 @@ sub cmd {
 
        my $r_len = $port->read(3);
 
-       while ( ! $r_len ) {
+       while ( length($r_len) < 3 ) {
                wait_device;
-               $r_len = $port->read(3);
+               $r_len = $port->read( 3 - length($r_len) );
        }
 
        wait_device;