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Improve baud-rate generation by using rounding-to-closest instead of truncation in divisor calculation. Results have been verified by logic analyzer on an FT232RT (232BM) chip. The following table shows the wanted baud rate, the baud rate obtained with the old method (truncation), with the new method (rounding) and the baud rate generated by the windows 10 driver. The numbers in parentheses is the error. +- Wanted --+------ Old -------+------ New -------+------ Win -------+ | 9600 | 9600 (0.00%) | 9604 (0.05%) | 9605 (0.05%) | | 19200 | 19200 (0.00%) | 19199 (0.01%) | 19198 (0.01%) | | 38400 | 38395 (0.01%) | 38431 (0.08%) | 38394 (0.02%) | | 57600 | 57725 (0.22%) | 57540 (0.10%) | 57673 (0.13%) | | 115200 | 115307 (0.09%) | 115330 (0.11%) | 115320 (0.10%) | | 921600 | 919963 (0.18%) | 920386 (0.13%) | 920810 (0.09%) | | 961200 | 996512 (3.67%) | 956480 (0.49%) | 956937 (0.44%) | +-----------+------------------+------------------+------------------+ The error due to noise in the measurements is in the order of a few tenths of a %. As can be seen, the baud rate is significantly improved for some rates (e.g. 961200), and corresponds to the output given by the windows driver. The theoretical baud rate has been calculated for all baud rates from 1 to 3M, and as expected, the error is centered around 0, with a triangle shape instead of a sawtooth, so the maximum error is decreased to half. Signed-off-by: Nikolaj Fogh <nikolajfogh@gmail.com> [ johan: edit commit message slightly ] Signed-off-by: Johan Hovold <johan@kernel.org> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
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the problems which may result by upgrading your kernel.