unit Unit1;

interface

uses
 Windows;

type
 TComPort = class
 private
 hFile: THandle;
 public
 constructor Create;
 destructor Destroy; override;
 function InitCom(BaudRate, PortNo: Integer; Parity: Char;
 CommTimeOuts: TCommTimeouts): Boolean;
 procedure CloseCom;
 function ReceiveCom(var Buffer; Size: DWORD): Integer;
 function SendCom(var Buffer; Size: DWORD): Integer;
 function ClearInputCom: Boolean;
 end;

implementation

uses
 SysUtils;

constructor TComPort.Create;
begin
 inherited;
 CloseCom;
end;

destructor TComPort.Destroy;
begin
 CloseCom;
 inherited;
end;

function TComPort.InitCom(BaudRate, PortNo: Integer; Parity: Char;
 CommTimeOuts: TCommTimeouts): Boolean;
var
 FileName: string;
 DCB: TDCB;
 PortParam: string;
begin
 result := FALSE;
 FileName := 'Com' + IntToStr(PortNo); {имя файла}
 hFile := CreateFile(PChar(FileName),
 GENERIC_READ or GENERIC_WRITE, 0, nil,
 OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);
 if hFile = INVALID_HANDLE_VALUE then
 exit;

 //установка требуемых параметров
 GetCommState(hFile, DCB); //чтение текущих параметров порта
 PortParam := 'baud=' + IntToStr(BaudRate) + ' parity=' + Parity +
 ' data=8 stop=1 ' +
 'octs=off';
 if BuildCommDCB(PChar(PortParam), DCB) then
 begin
 result := SetCommState(hFile, DCB) and
 SetCommTimeouts(hFile, CommTimeOuts);
 end;
 if not result then
 CloseCom;
end;

procedure TComPort.CloseCom;
begin
 if hFile < > INVALID_HANDLE_VALUE then
 CloseHandle(hFile);
 hFile := INVALID_HANDLE_VALUE;
end;

function TComPort.ReceiveCom(var Buffer; Size: DWORD): Integer;
var
 Received: DWORD;
begin
 if hFile = INVALID_HANDLE_VALUE then
 raise Exception.Create('Не открыта запись в Com порт');
 if ReadFile(hFile, Buffer, Size, Received, nil) then
 begin
 Result := Received;
 end
 else
 raise Exception.Create('Ошибка приема данных: ' + IntToStr(GetLastError));
end;

function TComPort.SendCom(var Buffer; Size: DWORD): Integer;
var
 Sended: DWORD;
begin
 if hFile = INVALID_HANDLE_VALUE then
 raise Exception.Create('Не открыта запись в Com порт');
 if WriteFile(hFile, Buffer, Size, Sended, nil) then
 begin
 Result := Sended;
 end
 else
 raise Exception.Create('Ошибка передачи данных: ' + IntToStr(GetLastError));
end;

function TComPort.ClearInputCom: Boolean;
begin
 if hFile = INVALID_HANDLE_VALUE then
 raise Exception.Create('Не открыта запись в Com порт');
 Result := PurgeComm(hFile, PURGE_RXCLEAR);
end;

end.