f0faebb3a1
On some systems a small delay is required between receiving the response of a packet and sending the request for the next packet. Without this delay, almost every request fails with either a NAK or a timeout. Retrying usually works, but also causes the download to slow down considerable. The root of the problem appears to be related to the FTDI low latency setting. On Windows and Mac OS X systems, the default setting for the latency is 16ms, while Linux defaults to a low latency setting of only 1ms. This higher latency on Windows and Mac automatically introduces a small delay while reading the packet, and that probably happens to be just enough to make the transfer succeed without any problems. But on Linux, due to the low latency setting, the next request is send almost immediately, and that causes the transfer to fail. I suspect the dive computer may still be busy with the previous request and needs a bit more time before it's ready to accept a new request. To mitigate this problem, we introduce a adaptive inter packet delay. Initially this adaptive delay is set to zero. This is to make sure we don't affect those systems that don't need a delay at all. Now, every time a packet fails, that's an indication the inter packet delay is too small, and we slightly increase the value. After a few attempts we'll automatically reach the minimal required value. To avoid that the delay grows out of control in the case of serious trouble, it's limited at 16ms. Note that the fixed 100ms delay before retrying a failed packet remains in place. That's on purpose, to make sure the next attempt will always be successful, regardless of whether the adaptive delay has already reached its minimal value or not.
Overview ======== Libdivecomputer is a cross-platform and open source library for communication with dive computers from various manufacturers. The official web site is: http://www.libdivecomputer.org/ The sourceforge project page is: http://sourceforge.net/projects/libdivecomputer/ Installation ============ On UNIX-like systems (including Linux, Mac OS X, MinGW), use the autotools based build system. Run the following commands from the top directory (containing this file) to configure, build and install the library and utilities: $ ./configure $ make $ make install If you downloaded the libdivecomputer source code directly from the git source code repository, then you need to create the configure script as the first step: $ autoreconf --install To uninstall libdivecomputer again, run: $ make uninstall Support ======= Please send bug reports, feedback or questions to the mailing list: http://libdivecomputer.org/cgi-bin/mailman/listinfo/devel or contact me directly: jef@libdivecomputer.org License ======= Libdivecomputer is free software, released under the terms of the GNU Lesser General Public License (LGPL). You can find a copy of the license in the file COPYING.