[avrdude-dev] Fwd: Win32 enhanced bitbang_delay

[Doug Brown]

Hi avrdude dev,

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.

Could someone incorporate this into the SVN? I've got no idea how to, & I'm
not on the dev team.

Regards,
Doug.

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 */
}