141 lines
5.8 KiB
Plaintext
141 lines
5.8 KiB
Plaintext
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RELIANCE EDGE
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Reliance Edge is a small, portable, highly reliable power-fail safe file
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system for resource-constrained embedded systems like microcontrollers.
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It is written in C and provides a familiar POSIX-like file system API,
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making it easy to use in your application; or an alternate minimalist
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API if your application has simple storage needs. Reliance Edge is
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highly configurable and can be tuned to the precise needs of your
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application.
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Getting Help
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You will find this section later in our readme as well - but we wanted
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to tell you up front: DATALIGHT WANTS TO HEAR FROM YOU! Whether it's
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just to make comments about the product, to suggest new features, or to
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tell us what you don't like - reach out! All comments and inquiries can
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be directed to RelianceEdgeSupport@datalight.com.
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Documentation
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The complete documentation for Reliance Edge is distributed separately.
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It includes an API reference and detailed discussions of various aspects
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of using Reliance Edge, including porting, building, configuring, and
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testing. This complete documentation, called the _Developer's Guide_,
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can be obtained for free from here:
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http://www.datalight.com/reliance-edge
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In addition this README, see doc/release_notes.md for a list of updates
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to Reliance Edge and a list of known issues. There is also a quick-start
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guide in the doc/ directory that describes step-by-step how to compile
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and run Reliance Edge in a simulated Windows environment.
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Why Use Reliance Edge?
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Reliance Edge is ideal for small embedded systems with data storage
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requirements, especially if there is a chance of sudden power loss or
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other system failures. Compared to "raw" disk access, using a file
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system like Reliance Edge removes the burden of tracking which sectors
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belong to which objects, and allows data to be updated more reliably.
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Compared to the FAT file system, using Reliance Edge eliminates the
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possibility that file system data will be left in an inconsistent state,
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corrupting the disk; Reliance Edge does not need a fsck/CHKDSK utility.
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Compared to journaling file systems, Reliance Edge has less overhead and
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results in less storage media wear for longer device lifetimes.
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Reliance Edge uses a unique transactional model that not only prevents
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file system corruption but also allows a set of changes to be made in an
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atomic "all or nothing" fashion. This is very useful for applications
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that make sets of interrelated changes. By using the features of
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Reliance Edge, a set of changes can be incorporated into a single atomic
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transaction, which is committed in its entirety or not at all even if
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interrupted by power loss; this means the application does not need code
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to recover from partially-finished updates.
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Hardware
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The typical hardware for Reliance Edge is a 32-bit microcontroller, but
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other targets are possible. In its typical configurations, Reliance Edge
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needs at least 4 KB to 5 KB of RAM, 11 to 18 KB of code space (on the
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ROM or NOR flash), and 500 to 700 bytes of stack.
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Reliance Edge is not designed for high-end embedded systems that run
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complicated operating systems like Linux or Windows Embedded Compact.
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Embedded systems of that variety are better served by other file
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systems, like Datalight's Reliance Nitro.
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Getting Reliance Edge Working
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Before you can use Reliance Edge, it must be ported and configured. At a
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minimum, porting includes filling-in functions so that Reliance Edge can
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issue commands to your storage medium; depending on your needs, other
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functions may need to be filled in as well. These functions reside in a
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subdirectory in the os/ directory; see os/stub/ for a blank set of
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functions. Configuring includes creating a project directory (start by
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copying projects/newproj) and creating the two configuration files
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(redconf.h/redconf.c) using the Reliance Edge Configuration Utility
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(which can be downloaded from http://www.datalight.com/reliance-edge).
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These topics are covered in much greater detail in the _Developer's
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Guide_, linked above.
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Using Reliance Edge
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Using Reliance Edge is a simple matter of including the primary Reliance
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Edge application header in your application (either include/redposix.h
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or include/redfse.h) and compiling and linking against Reliance Edge
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binaries. The Reliance Edge driver must be initialized before it is used
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(via the red_init() or RedFseInit() functions) and then volumes can be
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mounted and file and directory functions invoked. The Reliance Edge API
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is documented in the _Developer's Guide_ (linked above) and also via
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comments in the source code.
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Licensing
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Reliance Edge is an open-source project licensed under the GNU General
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Public License v2 (GPLv2). Businesses and individuals that for
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commercial or other reasons cannot comply with the terms of the GPLv2
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license may obtain a commercial license before incorporating Reliance
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Edge into proprietary software for distribution in any form. Visit
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http://www.datalight.com/reliance-edge for more information. The
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commercial distribution also includes extra tests and tools not
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distributed with the GPLv2 version.
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See LICENSE.txt for the full license terms of this distribution of the
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product.
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Getting Help
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If you need assistance using Reliance Edge, and you have already
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consulted the _Developer's Guide_, contact
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RelianceEdgeSupport@datalight.com.
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In the near future, a community forum or message board will be set up to
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facilitate discussion of Reliance Edge and allow users to get help from
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Datalight and from each other. In the meantime, please use the email
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address given above.
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Contributing
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Contributions to Reliance Edge are welcome. Our policy is that Datalight
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must own the copyright of all code incorporated into Reliance Edge; if
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contributing a significant amount of code, you will be asked to file a
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copyright assignment agreement. See CONTRIBUTING.txt for further details
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and contribution guidelines.
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To report bugs, please create a GitHub issue or contact
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RelianceEdgeSupport@datalight.com.
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