Re: Serial Communication in Visual C++

"Ryan Neuhart" <>
Wed, 11 Oct 2006 09:22:50 -0700
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);
  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).


"Duane Hebert" <> wrote in message

"Ryan Neuhart" <> wrote in message

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;

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?

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