我做过类似的东东，使用用Api查询访问串口实现的，给你个例子。
//-->初始化串口。
function init_comApi(Port: Integer): Integer;
Var aPort
AnsiChar;
sDCB:_DCB;
lp:CommTimeouts;
begin
//-->打开串口
aPort:=PChar(Format('COM%D',[Port+1]));
PortHandle:=CreateFile(aPort,GENERIC_READ or GENERIC_WRITE,0,Nil,
OPEN_EXISTING,0,0);
//Result:=PortHandle;
if PortHandle < 0 Then Begin
Result:=-1;Exit;
End;
//-->
if Not GetCommState(PortHandle,sDCB) then Begin
CloseHandle(PortHandle);
Result:=-1;Exit;
End;
sDCB.BaudRate:=CBR_57600;
sDCB.ByteSize:=8;
sDCB.Parity:=NOPARITY;
sDCB.StopBits:=ONESTOPBIT;
if Not SetCommState(PortHandle,sDCB) Then Begin
CloseHandle(PortHandle);
Result:=-1;Exit;
End;
lp.ReadIntervalTimeout :=MAXDWORD;
lp.ReadTotalTimeoutMultiplier:=0;
lp.ReadTotalTimeoutConstant:=0;
lp.WriteTotalTimeoutMultiplier:=0;
lp.WriteTotalTimeoutConstant:=0;
SetCommTimeouts(PortHandle,lp);
Result:=0;
end;
//-->接收一个Byte
Function rececodeApi(Time_Tlag:Byte;Var cData:Byte):Boolean;
Var iOldTime,iDelayTime:Integer;
lrc:LongWord;
_iDelayTime:Integer;
begin
Result:=True;
iOldTime:=0;iDelayTime:=0;_iDelayTime:=0;cData:=0;
Case Time_Tlag of
1:_iDelayTime:=40;//超时时间40=40ms
2:_iDelayTime:=500;
End;
iOldTime:=GetTickCount;
Repeat
if Not ReadFile(PortHandle,cData,1,lrc,Nil) Then
ClearCommError(PortHandle,lrc,Nil);
iDelayTime:=GetTickCount-iOldTime;
if iDelayTime>_iDelayTime Then Begin
Result:=False;Exit;
End;
Until lrc=1;
end;
//-->发送一个Byte
function sendcodeApi(cData: Byte): Boolean;
Var lrc:LongWord;
begin
Result:=True;
if Not WriteFile(PortHandle,cData,1,lrc,Nil) Then Begin
ClearCommError(PortHandle,lrc,Nil);
Result:=False;
End;
end;
