这段代码错在哪里？（关于spcomm发送问题）球大虾看看！！(50分)

代码如下，为何spcomm总是发送错误
===========================

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, ExtCtrls, StdCtrls, ComCtrls, SPComm, jpeg, Unit2;

type
TForm1 = class(TForm)
GroupBox1: TGroupBox;
Edit1: TEdit;
Button1: TButton;
Panel1: TPanel;
Panel2: TPanel;
ProgressBar1: TProgressBar;
Label1: TLabel;
Button2: TButton;
Button3: TButton;
Edit2: TEdit;
Label2: TLabel;
SpComm: TComm;
OpenDialog: TOpenDialog;
Image1: TImage;
Label3: TLabel;
Edit3: TEdit;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
private
FileHandle, // 文件名柄变量
FileLength, //源文件大小变量
num, //源文件被分割后的文件数目
iBytesRead : integer;
buf1 : integer; //文件缓冲区变量

{ Private declarations }
function wFileSize(AFileName:string):integer;
public
{ Public declarations }
end;

const
AFileSize=255;
var
Form1: TForm1;

implementation

//uses Unit2;

{$R *.dfm}

function TForm1.wFileSize(AFileName:string):integer;
var
F: file of Byte;
begin
try
AssignFile(F,AFileName);
Reset(F);
Result:=FileSize(F);
CloseFile(F); //
FileLength:=Result;
except
Result :=0;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
if OpenDialog.Execute then
begin
edit1.Text:=OpenDialog.FileName;
Image1.Picture.LoadFromFile(OpenDialog.FileName);
edit2.Text:=inttostr(wFileSize(OpenDialog.FileName));
end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
Form2.ShowModal;
end;



procedure TForm1.Button3Click(Sender: TObject);
var Buffer:array of PChar;
i,temp:integer;
pszBuffer: PChar;
begin
buf1:= AFileSize;
num := Round(FileLength/AFileSize+1);
SetLength(Buffer,num+2);
//ShowMessage(inttostr(num));
temp:=buf1;
ProgressBar1.Max:=num;//设置进度条状态
ProgressBar1.Position:=0;

for i:=1 to num do
begin
pszBuffer := PChar(AllocMem(buf1));
try
if i=num then
begin
pszBuffer := PChar(AllocMem(FileLength-buf1*(num-1)));
temp:=FileLength-buf1*(num-1);
end;
FileHandle:=FileOpen(edit1.Text,fmOpenRead);
FileSeek(FileHandle,buf1*(i-1),0);
iBytesRead := FileRead(FileHandle, pszBuffer^, temp);

FileClose(FileHandle);
spcomm.ByteSize:=0;

if not spcomm.WriteCommData(pszBuffer,temp) then
begin
ShowMessage('发送错误，终止发送');
//ProgressBar1.Max:=1;

ProgressBar1.Position:=0;
break;
end;
ProgressBar1.Position:=i;
sleep(2);
finally
FreeMem(pszBuffer);
end;
end;
//ShowMessage('ok');
end;

end.

在写数据前，要spcomm.startcomm以打开串口。

打开了还是不行

procedure TForm1.Button3Click(Sender: TObject);
var Buffer:array of PChar;
i,temp:integer;
pszBuffer: PChar;
begin
buf1:= AFileSize;
num := Round(FileLength/AFileSize+1);
SetLength(Buffer,num+2);
//ShowMessage(inttostr(num));
temp:=buf1;
ProgressBar1.Max:=num;//设置进度条状态
ProgressBar1.Position:=0;

SpComm.StartComm;
for i:=1 to num do
begin
pszBuffer := PChar(AllocMem(buf1));
try
if i=num then
begin
pszBuffer := PChar(AllocMem(FileLength-buf1*(num-1)));
temp:=FileLength-buf1*(num-1);
end;
FileHandle:=FileOpen(edit1.Text,fmOpenRead);
FileSeek(FileHandle,buf1*(i-1),0);
iBytesRead := FileRead(FileHandle, pszBuffer^, temp);

FileClose(FileHandle);
//spcomm.ByteSize:=0;

if not spcomm.WriteCommData(pszBuffer,temp) then
begin
ShowMessage('发送错误，终止发送');
//ProgressBar1.Max:=1;

ProgressBar1.Position:=0;
break;
end;
ProgressBar1.Position:=i;
sleep(2);
finally
FreeMem(pszBuffer);
end;
end;
//ShowMessage('ok');
end;

大虾帮帮忙啊

太乱了，看不明白，先简化一下看行不行
串口最好有单独的打开和关闭按键处理
串口不要打开后立即就发或发送语句后紧接着就关