Re: Serial Communication in Visual C++

From:

"Ryan Neuhart" <ryan@bihrle.com>

Newsgroups:

microsoft.public.vc.language

Date:

Tue, 10 Oct 2006 16:14:19 -0700

Message-ID:

<65TWg.33627$iA5.18148@dukeread11>

Ok, here's the whole function for initializing the comm port....

bool CCommTalk::InitPort(LPCSTR szPortName, LPCSTR szDCB){
ClosePort();

DCB Parms;
bool bInit = false;

m_hCommPort = INVALID_HANDLE_VALUE;

  for (;;) {
   m_hCommPort = CreateFile (
    szPortName,
    GENERIC_READ|GENERIC_WRITE,
    0 ,
    NULL ,
    OPEN_EXISTING,
    FILE_ATTRIBUTE_SYSTEM,
    NULL
    );

   if (m_hCommPort == INVALID_HANDLE_VALUE)
    break;

   if (!GetCommState(m_hCommPort, &Parms))
    break;

   Parms.BaudRate = CBR_9600;
   Parms.ByteSize = 8;
   Parms.Parity = NOPARITY;
   Parms.StopBits = ONESTOPBIT;

   SetCommState(m_hCommPort, &Parms);

   if (!SetCommState(m_hCommPort, &Parms))
    break;

   bInit = true;
   break;
  }

  if (!bInit) {
   CloseHandle(m_hCommPort);
   m_hCommPort=INVALID_HANDLE_VALUE;
  }

return bInit;
};

-Ryan

"Carl Daniel [VC++ MVP]" <cpdaniel_remove_this_and_nospam@mvps.org.nospam>
wrote in message news:%23IEI$$J7GHA.3620@TK2MSFTNGP04.phx.gbl...

"Ryan Neuhart" <ryan@bihrle.com> wrote in message
news:z1SWg.33625$iA5.27860@dukeread11...

Hello,
I am communicating with a programmable power supply using an RS-232
interface through Visual Studio and having a slight problem. The power
supply documentation supplied very little information about communicating
this way except for the following:

   Baud Rate: 1200, 2400, 4800, or 9600
   Parity Bit: none
   Data Bit: 8 bits
   Stop Bit: 1 stop bit
   Data flow control: none

I have set up a DCB (Platform SDK) structure in code and am able to
actually
communicate with the power supply and it carries out the action I ask it
to,
but it is painfully slow (on the order of 2-3 seconds per command). The
following is what I have set up in code (as far as serial parameters are
concerned):

   DCB Parms;
   Parms.BaudRate = CBR_9600;
   Parms.ByteSize = 8;
   Parms.Parity = NOPARITY;
   Parms.StopBits = ONESTOPBIT;

and again, this works, but it is running way too slow for the current
purposes. I have carried out the same actions through MATLAB's serial
interface and also just through HyperTerminal (Start
Menu-->Accessories-->Communications) and the power supply responds
instantaneously to inputs through those interfaces.

Can anybody provide any guidance as to what I can do to achieve
instantaneous responses through Visual Studio? Thanks in advance.

Your problem lies in code you haven't shown. Please post a minimal
program that reproduces the problem you're seeing. It's not uncommon that
in the process of producing a minimal example, you'll discover what's
wrong with your application.

-cd