Re: Reading Serial Port

From:

"David Ching" <dc@remove-this.dcsoft.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Wed, 30 Jan 2008 04:41:51 -0800

Message-ID:

<jg_nj.5218$so6.4279@newssvr19.news.prodigy.net>

"clinisbut" <clinisbut@gmail.com> wrote in message
news:5edcd8e2-2a6c-4276-aade-844e41317c6f@s12g2000prg.googlegroups.com...

If you are wondering why I'm reading justa a byte each time when all
frames are 16 bytes length it's because this is just a test, in the
final version the device will send variable frame lengths.

I do remember having to set the timeouts appropriately or would get bad
data. Before writing data, I set a 0 timeout, and set a 1 second timeout
for readind data. Here's an example code snippet using the Naughter
library:

  try
  {
   // Ask device to write back its current time
   m_port.Set0Timeout(); // don't ever block, just return any chars already
arrived at port when port.Read() is called
   BYTE cmd = 0x27; // READ_TIME
   if ( m_port.Write (&cmd, 1) == 1 )
   {
    // Read data that device sent back. Wait up to 1 second for the data to
be received before timing out
    COMMTIMEOUTS timeouts;
    timeouts.ReadIntervalTimeout = 0;
    timeouts.ReadTotalTimeoutMultiplier = 0;
    timeouts.ReadTotalTimeoutConstant = 1000; // 1000 ms
    timeouts.WriteTotalTimeoutMultiplier = 0;
    timeouts.WriteTotalTimeoutConstant = 0;
    m_port.SetTimeouts(timeouts);

    // Reads 4 bytes
    BYTE bytesTime[4];
    ZeroMemory(bytesTime, sizeof(bytesTime));
    if ( m_port.Read (bytesTime, _countof(bytesTime)) ==
_countof(bytesTime) )
    {
     ...
    }
   }
  }
  catch (CSerialException *)
  {
   bShowError = TRUE;
  }

-- David