检查RS232(串口)是否接有设备

在RS232中有4个脚位可用来回应讯号给电脑分別为CTS,DSR,RING,RLSD当未接上设备时,脚位的电太皆为低电压,讯号传回OFF,很多设备都利用此四个脚位与电脑沟通,所以检查脚位电压就知道改COM上是否有设备存在

MS_CTS_ON,MS_DSR_ON,MS_RING_ON,MS_RLSD_ON

procedure TForm1.Button1Click(Sender: TObject);

var

cc:TCommConfig;

hComm:THandle;

Com:String;

lS:dword;

begin

Com:='COM2';

hComm:=CreateFile(Pchar(Com),Generic_read or Generic_write,0,nil,open_existing,0,0);

if GetCommModemStatus(hcomm,lS) then

begin

if(ls and MS_CTS_ON)=MS_CTS_ON then

begin

Button1.Caption:='CTSON'

end;

end;

closeHandle(hcomm);

end;

(作者 anykey)

end.

2.检查Handle所得到的值

procedure TForm1.Button1Click(Sender: TObject);

var

cc:TCommConfig;

hComm:THandle;

Com:String;

lS:dword;

begin

Com:='COM2';

hComm:=CreateFile(Pchar(Com),Generic_read or Generic_write,0,nil,open_existing,0,0);

if(hComm=invalid_Handle_value) then

begin

showmessage('通讯口错误);

end;

closeHandle(hcomm);

end;(作者 anykey)