4b869dd71d
I2C_SET was quite inflexible, it used too long delays as well as some unnecessary delays. The new building blocks are iicbb_clockin and iicbb_clockout. The former sets SDA and starts the high period of SCL, the latter executes the low period of SCL. What happens during the high phase depends on the operation. For writes we just hold both lines, for reads we poll SDA. S, Sr and P change SDA in the middle of the high period. Also, the calculation of udelay has been updated, so that the resulting period more closely corresponds the requested bus frequency. There is a new knob, io_delay, that allows to further adjust udelay based on the estimated latency of pin toggling operations. Finally, I slightly changed debug tracing and added error indicators to it. The debug prints are compiled in but disabled by default. This can be of use if there is any fallout from this change. Some ideas for further improvements: - add a function for sub-microsecond delays (e.g., in units of 1/10th of a microsecond) and use it for more precise timing of short delays; - account for the actual time spent in the pin I/O. Some sample debug output with the new code follows. Reading temperature and humidity from HTU21 in the bus hold mode: <<w80+ we3+ <w81+ .....r6d+ rac+ r94- >> <<w80+ we5+ <w81+ .............r47+ re2+ r84- >> where '<<' is S, '<' is Sr, '>>' is P, '.' is one millisecond of clock stretching by the slave. Reading temperature and humidity in the no-hold mode: <<w80+ wf3+ >> <<w81- >> <<w81+ r6d+ r54+ raf- >> <<w80+ wf5+ >> <<w81- >> <<w81+ r48+ r4e+ r9c- >> where '+' is Ack and '-' is NoAck. We see that first read attempts are not acknowledged. MFC after: 4 weeks Differential Revision: https://reviews.freebsd.org/D22206 |
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|---|---|---|
| bin | ||
| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| stand | ||
| sys | ||
| targets | ||
| tests | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| .arcconfig | ||
| .arclint | ||
| .cirrus.yml | ||
| .clang-format | ||
| .gitattributes | ||
| .gitignore | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| Makefile.libcompat | ||
| Makefile.sys.inc | ||
| ObsoleteFiles.inc | ||
| README | ||
| README.md | ||
| RELNOTES | ||
| UPDATING | ||
FreeBSD Source:
This is the top level of the FreeBSD source directory. This file
was last revised on:
FreeBSD
FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms. A large community has continually developed it for more than thirty years. Its advanced networking, security, and storage features have made FreeBSD the platform of choice for many of the busiest web sites and most pervasive embedded networking and storage devices.
For copyright information, please see the file COPYRIGHT in this directory. Additional copyright information also exists for some sources in this tree - please see the specific source directories for more information.
The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree. See build(7), config(8), https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html, and https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html for more information, including setting make(1) variables.
Source Roadmap:
bin System/user commands.
cddl Various commands and libraries under the Common Development
and Distribution License.
contrib Packages contributed by 3rd parties.
crypto Cryptography stuff (see crypto/README).
etc Template files for /etc.
gnu Various commands and libraries under the GNU Public License.
Please see gnu/COPYING* for more information.
include System include files.
kerberos5 Kerberos5 (Heimdal) package.
lib System libraries.
libexec System daemons.
release Release building Makefile & associated tools.
rescue Build system for statically linked /rescue utilities.
sbin System commands.
secure Cryptographic libraries and commands.
share Shared resources.
stand Boot loader sources.
sys Kernel sources.
sys/<arch>/conf Kernel configuration files. GENERIC is the configuration
used in release builds. NOTES contains documentation of
all possible entries.
tests Regression tests which can be run by Kyua. See tests/README
for additional information.
tools Utilities for regression testing and miscellaneous tasks.
usr.bin User commands.
usr.sbin System administration commands.
For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see:
https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/current-stable.html