我写了一个对串行口写数据的函数，可是一个字符也写不进去，一直在while循环中等待的

Question

Please help me！我写了一个对串行口写数据的函数，可是一个字符也写不进去，一直在while循环中等待的
（在线等待）
function Write(var OutBuf:Pchar; NumberOfBytesToWrite:DWord):Byte;
var
  WriteOverlap:Toverlapped;
  WhereToStartWriting,NumberOfBytesWritten:DWord;
begin
  if (NumberOfBytesToWrite=0) then
  begin
    {Output buffer is empty}
    result:=6;
    exit;
  end;
  WhereToStartWriting:=0;
  NumberOfBytesWritten:=0;
  FillChar(WriteOverlap,Sizeof(WriteOverlap),0);
  WriteOverlap.hEvent:=CreateEvent(NIL,FALSE,FALSE,NIL);
  if WriteOverlap.hEvent=null then
  begin
    {CreatEvent error}
    result:=7;
    exit;
  end;
  SetCommMask(CommHandle,EV_TXEMPTY);
  While (NumberOfBytesToWrite>0) do
  begin
    if not WriteFile(CommHandle,OutBuf [WhereToStartWriting],NumberOfBytesToWrite,NumberOfBytesWritten,@WriteOverlap) then
    begin
      if (GetLastError=ERROR_IO_PENDING) then
      begin
        WaitForSingleObject(WriteOverlap.hEvent,INFINITE);
        GetOverlappedResult(CommHandle,WriteOverlap,NumberOfBytesWritten,False);
      end
      else begin
        {Write error}
        CloseHandle(WriteOverLap.hEvent);
        result:=8;
        exit;
      end;
    end
    else begin
    Dec(NumberOfBytesToWrite,NumberOfBytesWritten);
    Inc(WhereToStartWriting,NumberOfBytesWritten);
    end;
  end;//EndWhile
  CloseHandle(WriteOverLap.hEvent);
  result:=0;
end;

Answer 1

你用的是文件句柄，我没有用过，我是用的控件来实现的。spcomm控件很方便。

Answer 2

我用过的方法
VAR
hcm:Thandle;
  hdcb:TDCB;
  num:DWORD;
  p:pchar;
  i:integer;
  s:string;
  m_length:integer;
begin
  getmem(p,25);  
  s:=edit2.Text;
  m_length:=length(s);
  strcopy(p,pchar(s));
  hcm := CreateFile('com1',GENERIC_READ or GENERIC_WRITE,0,nil,OPEN_EXISTING,0,0);
    if hcm<>0 then
    begin
      try
        zeromemory(@hdcb,sizeof(TDCB));
        hdcb.DCBlength := sizeof(TDCB);
        hdcb.BaudRate  := 19200;
        hdcb.ByteSize  := 8;
        hdcb.Parity    := NOParity;
        hdcb.StopBits  := ONESTOPBIT;        
        if (SetCommState(hcm,hdcb)) then
        begin
          FOR I:=0 TO M_LENGTH-1 DO
          begin
           sleep(1);
           WriteFile(hcm,p[I],1,num,nil);           
          end;           
        end;
      finally
        CloseHandle(hcm);
      end;
      freemem(p,25);
end;

Answer 3

我知道错在什么地方了，呵呵！把中间一段的else begin去掉就ok了
if not WriteFile(CommHandle,OutBuf [WhereToStartWriting],NumberOfBytesToWrite,NumberOfBytesWritten,@WriteOverlap) then
    begin
      if (GetLastError=ERROR_IO_PENDING) then
      begin
        WaitForSingleObject(WriteOverlap.hEvent,INFINITE);
        GetOverlappedResult(CommHandle,WriteOverlap,NumberOfBytesWritten,False);
      end
      else begin
        {Write error}
        CloseHandle(WriteOverLap.hEvent);
        result:=8;
        exit;
      end;
    end;
    Dec(NumberOfBytesToWrite,NumberOfBytesWritten);
    Inc(WhereToStartWriting,NumberOfBytesWritten);