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<HTML
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><HEAD
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>Programming With eCos</TITLE
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"><LINK
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REL="HOME"
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TITLE="eCos User Guide"
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HREF="ecos-user-guide.html"><LINK
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REL="UP"
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TITLE="Programming With eCos"
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HREF="user-guide-programming.html"><LINK
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REL="PREVIOUS"
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TITLE="Programming With eCos"
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HREF="user-guide-programming.html"><LINK
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REL="NEXT"
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TITLE="Configuring and Building eCos from Source"
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HREF="configuring-and-building-ecos-from-source.html"></HEAD
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>eCos User Guide</TH
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>Prev</A
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HREF="configuring-and-building-ecos-from-source.html"
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>Next</A
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><H1
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><A
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NAME="PROGRAMMING-WITH-ECOS">Chapter 10. Programming With <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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></H1
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><P
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>The following chapters of this manual comprise a simple tutorial
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for configuring and building <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>, building and running <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> tests,
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and finally building three stand-alone example programs which use
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the <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> API to perform some simple tasks.</P
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><P
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>You will need a properly installed <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> system, with the correct
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versions of the GNU toolchain. On Windows
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you will be using the bash command line interpreter that comes with
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Cygwin, with the environment variables set as described in the
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toolchain documentation.</P
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NAME="DEVELOPMENT-PROCESS">The Development Process</H1
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>Most development projects using <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> would contain some (or
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most) of the following:</P
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NAME="AEN471"><SPAN
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>eCos</SPAN
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> Configuration</H2
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><SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> is configured to provide the desired API (the inclusion
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of libc, uitron, and the disabling of certain undesired funtions,
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etc.), and semantics (selecting scheduler, mutex behavior, etc.).
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See <A
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HREF="configuring-and-building-ecos-from-source.html"
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>Chapter 11</A
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>.</P
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><P
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>It would normally make sense to enable <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> assertion checking
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at this time as well, to catch as many programming errors during
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the development phase as possible.</P
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><P
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>Note that it should not be necessary to spend much time on
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<SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> configuration initially. It may be important to perform fine
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tuning to reduce the memory footprint and to improve performance
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later when the product reaches a testable state.</P
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><A
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NAME="AEN481">Integrity check of the <SPAN
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>eCos</SPAN
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> configuration</H2
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><P
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>While we strive to thoroughly test <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>, the vast number
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of configuration permutations mean that the particular configuration
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parameters used for your project may not have been tested. Therefore,
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we advise running the <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> tests after the project's
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<SPAN
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>eCos</SPAN
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> configuration has been determined. See <A
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HREF="running-an-ecos-test-case.html"
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>Chapter 12</A
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>.</P
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><P
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>Obviously, this should be repeated if the configuration changes
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later on in the development process.</P
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NAME="AEN490">Application Development - Target Neutral Part</H2
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><P
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>While your project is probably targeting a specific architecture
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and platform, possibly custom hardware, it may be possible to perform
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part of the application development using simulated or synthetic
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targets.</P
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><P
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>There are three good reasons for doing this:</P
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><P
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></P
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><UL
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><LI
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><P
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>It may be possible by this means to perform application
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development in parallel with the design/implementation
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of the target hardware, thus providing more time for developing
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and testing functionality, and reducing time-to-market.</P
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></LI
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><LI
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><P
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>The build-run-debug-cycle may be faster when the application
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does not have to be downloaded to a target via a serial interface.
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Debugging is also likely to be more responsive when you do not have to
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to communicate with the remote GDB stubs in RedBoot via serial. It
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also removes the need for manually or automatically resetting the
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target hardware.</P
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></LI
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><LI
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><P
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>New hardware can often be buggy. Comparing the behaviour of the
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program on the hardware and in the simulator or synthetic target may
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allow you to identify where the problems lie.</P
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></LI
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></UL
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><P
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>This approach is possible because all targets (including
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simulators and synthetic ones) provide the same basic API: that
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is, kernel, libc, libm, uitron, infra, and to some extent, HAL and
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IO.</P
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><P
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>Synthetic targets are especially suitable as they allow you
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to construct simulations of elaborate devices by interaction with
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the host system, where an IO device API can hide the details from
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the application. When switching to hardware later in the development
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cycle, the IO driver is properly implemented.</P
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><P
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>Simulators can also do this, but it all depends on the
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design and capabilities of the simulator you use. Some, like
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<A
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HREF="http://sources.redhat.com/sid"
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TARGET="_top"
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>SID</A
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> or
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<A
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HREF="http://bochs.sourceforge.net/"
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TARGET="_top"
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>Bochs</A
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> provide
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complete hardware emulation, while others just support enough of the
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instruction set to run compiled code.</P
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><P
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>Therefore, select a simulator or synthetic target and use
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it for as long as possible for application development. That is,
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configure for the selected target, build <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>, build the application
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and link with <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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>, run and debug. Repeat the latter two steps until
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you are happy with it.</P
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><P
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>Obviously, at some time you will have to switch to the intended
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target hardware, for example when adding target specific feature
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support, for memory footprint/performance characterization,
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and for final tuning of <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> and the application.</P
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></DIV
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><DIV
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><A
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NAME="AEN511">Application Development - Target Specific Part</H2
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><P
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>Repeat the build-run-debug-cycle while performing final tuning
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and debugging of application. Remember to disable <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> assertion
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checking if you are testing any performance-related aspects, it can
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make a big difference.</P
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><P
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>It may be useful to switch between this and the previous step
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repeatedly through the development process; use the simulator/synthetic
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target for actual development, and use the target hardware to continually
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check memory footprint and performance. There should be little cost
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in switching between the two targets when using two separate build
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trees. </P
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></DIV
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WIDTH="100%"><TABLE
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HREF="user-guide-programming.html"
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ACCESSKEY="P"
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>Prev</A
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ALIGN="center"
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>Home</A
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HREF="configuring-and-building-ecos-from-source.html"
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ALIGN="left"
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>Programming With <SPAN
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>eCos</SPAN
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="user-guide-programming.html"
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ACCESSKEY="U"
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>Up</A
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Configuring and Building <SPAN
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CLASS="PRODUCTNAME"
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>eCos</SPAN
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> from Source</TD
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></TR
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></TABLE
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></DIV
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| 368 |
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></BODY
|
| 369 |
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></HTML
|
| 370 |
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>
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