Example :

:1005AA00000102030405060708090A0B0C0D0E0F88
^----------- use for calculate check sum ----------^^^
|_|
Check sum__|
RECLEN = 0x10 = 16
ADDRESS = 0x05AA
RECTYPE = 00
DATA = 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F
CHKSUM = 0x88 = 256 -sum(0x00+..+0x0F)= 256- 0x78














type buffer=array of byte; //assign as Dynamic array
var HexBuf:buffer;

function readline(HexLine:string; var Buf:buffer):integer;
var ADDR,count:integer;
CHKSUM,SUMLINE,RECLEN,RECTYPE,DATA:byte;
t:shortstring;
begin
// Array length may be change, here is 100,000
SetLength(HexBuf,100000);
if HexLine[1]=':' then begin
t:='$'+copy(HexLine,2,2); // get length
RECLEN:=strtoint(t);
CHKSUM:=0;
CHKSUM:=CHKSUM+RECLEN;
t:='$'+copy(HexLine,4,4); // get address
ADDR:=strtoint(t);
CHKSUM:=CHKSUM+lo(ADDR)+hi(ADDR);
t:='$'+copy(HexLine,8,2);
RECTYPE:=strtoint(t);
CHKSUM:=CHKSUM+RECTYPE;
case RECTYPE of
0:begin // datablock
count:=0;
while (count < RECLEN) do begin
t:='$'+copy(HexLine,10+2*count,2);
DATA:=strtoint(t);
CHKSUM:=CHKSUM+DATA;
Buf[ADDR+count]:=DATA;
inc(count);
end;
t:='$'+copy(HexLine,10+2*count,2);
SUMLINE:=strtoint(t);
end;
1:begin // end of file
t:='$'+copy(HexLine,10,2);
SUMLINE:=strtoint(t);
result:=1;
end;
else
begin
result := -2; // invalid record type
exit;
end;
end; //case
// test checksum
DATA:=SUMLINE+CHKSUM;
if (DATA<>0) then result:=-3; // checksum error
end
else result:=-1; // no record
end;




To use this routine

Here is an example demonstration how to use the above readline routine

procedure TForm1.Button1Click(Sender: TObject);
var Fname,line:string;
Fp : textfile;
ErrorCode:integer;
begin
Fname:='test.hex';
AssignFile(Fp,Fname); { File selected in dialog }
Reset(Fp);
while not eof(Fp) do
begin
Readln(Fp, line);{ Read first line of file }
ErrorCode := readline(line,HexBuf);
if (ErrorCode=0) then
begin
// Do some thing if read one line OK
// such send data to serial port,parallel port etc.
end
else
begin
// Error handle here
// 0 = No error
// -1 = File not Intel Hex format
// -2 = Invalid record type
// -3 = Checksum error
break; // exit while loop
end;
end;
CloseFile(Fp);
end;