# APRS passcode calculator
#
# Calculate the "passcode" ("callpass") needed for some APRS applications
#
# Copyright (C) 2012-2025 Christophe DAVID ( ON6ZQ | AC6ZQ )

clear;  # Clear all variables

callsign = "XY3ABC";            # Bare callsign (no -5, no /P, etc.)
passcode = uint16(29666);
callsign = upper(callsign);     # Convert to uppercase

for i = 1:2:length(callsign)
    a = uint16(callsign(i));    # ASCII value of character
    passcode = bitxor(passcode, a * 256);

    if i < length(callsign)
        b = uint16(callsign(i + 1));
        passcode = bitxor(passcode, b);
    end
end

passcode = bitand(passcode, uint16(32767));

printf("\nThe passcode for %s is %d\n", callsign, passcode);