KISS-C windows download speed

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bsilver
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I was working on USB downloads to the CBC from Windows for an Eclipse plugin I'm writing. I found that changing what was 4 calls to the Windows API write function in my code (I'm not sure how many the KISS-C QT code ends up with) per packet to 1 reduced download times by ~40%.

The lines in KISS-C that are (through QT) calling the WriteFile function are

  1. m_stream << SERIAL_KEY;
  2. m_stream << data;
  3. m_stream << qChecksum(data.constData(), data.size());
in kiss/targets/cbc2/src/SerialClient.cpp. I'm not sure how many calls through to the Windows API these 3 lines result in, but it's probably at least 3.

I also discovered that download times can be sped up a little bit by changing

  1. cto.ReadIntervalTimeout = 500;
  2. cto.ReadTotalTimeoutMultiplier = 0;
  3. cto.ReadTotalTimeoutConstant = 500;
to
  1. cto.ReadIntervalTimeout = MAXDWORD;
  2. cto.ReadTotalTimeoutMultiplier = MAXDWORD;
  3. cto.ReadTotalTimeoutConstant = 200;
in file kiss/targets/cbc2/src/QSerialPort.cpp to reduce the time it spends waiting for responses on failed packets.

The line numbers in the code are correct as of commit 3df33d25203f45ae1e9766a4229a03f4fbbf2280.

Jeremy Rand
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Nice work... I don't think KIPR noticed this thread; you might want to directly contact KIPR to get this fixed. I recall that Stephen Carlson found some similar issues last year with the KISS-C download speed in Windows, using a serial monitor. I don't believe KIPR ever used his research. :-(

-Jeremy Rand
Senior Programmer, Team SNARC (2012-2013), Norman Advanced (2010-2011), Norman HS (2008-2009), Norman North (2005-2007), Whittier MS (2003-2004)
2012-2013 VP of Tech, 2011 President, Botball YAC (2009-2013)
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