delphi 485 代码

以下是一个简单的 Delphi 代码示例，用于通过 RS485 协议进行通信：

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

const
  // 串口号
  COM_PORT = 'COM1';
  // 波特率
  BAUD_RATE = 9600;
  // 数据位
  DATA_BITS = 8;
  // 停止位
  STOP_BITS = 1;
  // 校验位
  PARITY = NOPARITY;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Edit1: TEdit;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
    FComHandle: THandle;
    procedure WriteData(Data: AnsiString);
    function ReadData: AnsiString;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

// 打开串口
function OpenCom(Port: string; BaudRate: Integer; DataBits: Integer; StopBits: Integer; Parity: Integer): THandle;
var
  DCB: TDCB;
  PortHandle: THandle;
begin
  Result := INVALID_HANDLE_VALUE;

  PortHandle := CreateFile(PChar(Port), GENERIC_READ or GENERIC_WRITE, 0, nil, OPEN_EXISTING, 0, 0);
  if PortHandle = INVALID_HANDLE_VALUE then Exit;

  FillChar(DCB, SizeOf(DCB), 0);
  DCB.DCBlength := SizeOf(DCB);

  if not GetCommState(PortHandle, DCB) then Exit;

  DCB.BaudRate := BaudRate;
  DCB.ByteSize := DataBits;
  DCB.Parity := Parity;
  DCB.StopBits := StopBits;

  if not SetCommState(PortHandle, DCB) then Exit;

  Result := PortHandle;
end;

// 关闭串口
procedure CloseCom(Handle: THandle);
begin
  CloseHandle(Handle);
end;

// 写入数据
procedure TForm1.WriteData(Data: AnsiString);
var
  BytesWritten: DWORD;
begin
  if WriteFile(FComHandle, Data[1], Length(Data), BytesWritten, nil) then
  begin
    Memo1.Lines.Add('Write: ' + Data);
  end
  else
  begin
    Memo1.Lines.Add('Error writing to port');
  end;
end;

// 读取数据
function TForm1.ReadData: AnsiString;
var
  Buffer: array[0..1024] of AnsiChar;
  BytesRead: DWORD;
  i, j: Integer;
begin
  Result := '';
  if ReadFile(FComHandle, Buffer, SizeOf(Buffer), BytesRead, nil) then
  begin
    for i := 0 to BytesRead - 1 do
    begin
      if (Buffer[i] = #13) or (Buffer[i] = #10) then
      begin
        for j := 0 to i - 1 do
        begin
          Result := Result + Buffer[j];
        end;
        Exit;
      end;
    end;
  end
  else
  begin
    Memo1.Lines.Add('Error reading from port');
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  FComHandle := OpenCom(COM_PORT, BAUD_RATE, DATA_BITS, STOP_BITS, PARITY);
  if FComHandle = INVALID_HANDLE_VALUE then
  begin
    ShowMessage('Failed to open serial port');
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  WriteData(Edit1.Text + #13#10);
  Memo1.Lines.Add('Read: ' + ReadData);
end;

// 关闭串口
procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  CloseCom(FComHandle);
end;

end.

在这个示例中，我们使用 Windows API 来打开和关闭串口，使用 `WriteFile` 函数向串口写入数据，并使用 `ReadFile` 函数从串口读取数据。请注意，这个示例仅仅是一个简单的示例，你需要根据你的具体需求修改代码。