[avrdude-dev] [patch #7010] Win32 enhanced bitbang_delay

[Doug]

URL:
  <http://savannah.nongnu.org/patch/?7010>

                 Summary: Win32 enhanced bitbang_delay
                 Project: AVR Downloader/UploaDEr
            Submitted by: dougy83
            Submitted on: Wed 02 Dec 2009 09:37:40 AM GMT
                Category: None
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any

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Details:

I read that the bitbang_delay is not calibrated for Win32 so I wrote the
following code. It uses the performance counters which are high accuracy
hardware counters (3.6MHz on my 5 yr old laptop). If the counters are not
available, it falls back to the uncalibrated delay method. Seems to have a
~3us overhead on my laptop.


void bitbang_delay(int us)
{
#if defined(WIN32NATIVE)
  static LARGE_INTEGER freq;
  static enum {eNotInit, eInitOK, eInitFail}freqInit = eNotInit;

  if(freqInit == eNotInit)
  {
    if(!QueryPerformanceFrequency(&freq))
      freqInit = eInitFail;      // perf counters not available
    else
      freqInit = eInitOK;
  }

  if(freqInit == eInitOK)
  {
    LARGE_INTEGER countNow, countEnd;
    QueryPerformanceCounter(&countNow);
    countEnd.QuadPart = countNow.QuadPart + freq.QuadPart * us / 1000000ll;

    while (countNow.QuadPart < countEnd.QuadPart)
      QueryPerformanceCounter(&countNow);
  }
  else  // no performance counters -- run normal uncalibrated delay
  {
    volatile int del = us * delay_decrement;

    while (del > 0)
      del--;
  }

#else
  volatile int del = us * delay_decrement;

  while (del > 0)
    del--;
#endif /* WIN32NATIVE */
}





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