Question

After reading this very interesting topic on stackoverflow –> How to wait for COM port receive event before sending more data in a loop

I’ve ran into many problems and i’ve tried many solutions … nothing work well unfortunately !

Many serial port libraries are event-driven and i’m having a hard time understanding them.

I’ve tried with Asyncpro, Synaser and TComport.

Is it possible to have a function like this:

SerialSendandReply(tx string here,timeout) return rx string and if timeout send a error string

Response from the device are withing milliseconds a blocking way to do it would be better?

Like this:

Dosomething here
showmessage(SerialSendandReply('test',100 )); //100 ms timeout
dosomething else

With this code

TForm1 = class(TForm)
 ...
private
    IOEvent           : THandle; // used for IO events
    IORx              : string;
    Comport           : TapdComport;
...


procedure TForm1.ComportTriggerAvail(CP: TObject; Count: Word);

var i       : integer;

begin
 for i:=1 to Count do
  IORx:=IORx+Comport.GetChar;
 SetEvent(IOEvent);
end;

function TForm1.SerialSAWR(tx : string; TimeOut : integer) : boolean;
begin
 Result := False;
 try
  IORx := ''; // your global var
  ResetEvent(IOEvent);
  Comport.PutString(tx);
  Result := WaitForSingleObject(IOEvent, TimeOut) = WAIT_OBJECT_0;
 except
  on E : Exception do
   // dosomething with exception
 end;
end;

// constructor part
IOEvent := CreateEvent(nil, True, False, nil);
// destructor part
 if IOEvent <> 0 then
  CloseHandle(IOEvent);

Then i’ve tried to call this function :

if SerialSAWR('test'; 5000) then showmessage(IORx);

Sending is working great but doesn’t return anything in the string.

Any advices?

Thank you very much!

Regards,
Laurent

Answer 1

I switched for nrComm Lib (v9.31)… very simple of use and well supported.

The only drawback is that isn’t free and open source … but it’s worth it !

It’s also thread-safe which is good too :).

Thank you very much everyone for the replies!