Code:

function BCDToNumString(const inStr: string): string;

procedure UnPack(ch: Char; var ch1, ch2: Char);

begin

ch1 := Chr((Ord(ch) and$F) + $30);

ch2 := Chr(((Ord(ch) shr4) and$F) + $30);

Assert((ch1 >= '0') and (ch1 <= '9'));

Assert((ch2 >= '0') and (ch2 <= '9'));

end;

var

i: Integer;

begin

SetLength(Result, Length(inStr) * 2);

for i := 1to Length(inStr) do

UnPack(inStr[i], Result[2 * i - 1], Result[2 * i]);

end;

procedure TForm1.Button1Click(Sender: TObject);

var

S1, S2: string;

begin

S1 := '15151515151515151515';

S2 := NumStringToBCD(S1);

memo1.lines.add('S1: ' + S1);

memo1.lines.add('Length(S2): ' + IntToStr(Length(S2)));

memo1.lines.add('S2 unpacked again: ' + BCDToNumString(S2));

end;