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<!-- Copyright (C) 2003 Red Hat, Inc.                                -->
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>Programming With eCos</TITLE
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><DIV
CLASS="CHAPTER"
><H1
><A
NAME="PROGRAMMING-WITH-ECOS">Chapter 10. Programming With <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
></H1
><P
>The following chapters of this manual comprise a simple tutorial
for configuring and building <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
>, building and running <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> tests,
and finally building three stand-alone example programs which use
the  <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> API to perform some simple tasks.</P
><P
>You will need a properly installed <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> system, with the correct
versions of the GNU toolchain. On Windows
you will be using the bash command line interpreter that comes with
Cygwin, with the environment variables set as described in the
toolchain documentation.</P
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="DEVELOPMENT-PROCESS">The Development Process</H1
><P
>Most development projects using <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> would contain some (or
most) of  the following:</P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN471"><SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> Configuration</H2
><P
><SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> is configured to provide the desired API (the inclusion
of libc, uitron, and the disabling of certain undesired funtions,
etc.), and semantics (selecting scheduler, mutex behavior, etc.).
See <A
HREF="configuring-and-building-ecos-from-source.html"
>Chapter 11</A
>.</P
><P
>It would normally make sense to enable <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> assertion checking
at this time as well, to catch as many programming errors during
the development phase as possible.</P
><P
>Note that it should not be necessary to spend much time on
<SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> configuration initially. It may be important to perform fine
tuning to reduce the memory footprint and to improve performance
later when the product reaches a testable state.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN481">Integrity check of the <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> configuration</H2
><P
>While we strive to thoroughly test <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
>, the vast number
of configuration permutations mean that the particular configuration
parameters used for your project may not have been tested. Therefore,
we advise running the <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> tests after the project's
<SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> configuration has been determined. See <A
HREF="running-an-ecos-test-case.html"
>Chapter 12</A
>.</P
><P
>Obviously, this should be repeated if the configuration changes
later on in the development process.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN490">Application Development - Target Neutral Part</H2
><P
>While your project is probably targeting a specific architecture
and platform, possibly custom hardware, it may be possible to perform
part of the application development using simulated or synthetic
targets.</P
><P
>There are three good reasons for doing this:</P
><P
></P
><UL
><LI
><P
>It may be possible by this means to perform application
development in parallel with the design/implementation
of the target hardware, thus providing more time for developing
and testing functionality, and reducing time-to-market.</P
></LI
><LI
><P
>The build-run-debug-cycle may be faster when the application
does not have to be downloaded to a target via a serial interface.
Debugging is also likely to be more responsive when you do not have to
to communicate with the remote GDB stubs in RedBoot via serial. It
also removes the need for manually or automatically resetting the
target hardware.</P
></LI
><LI
><P
>New hardware can often be buggy. Comparing the behaviour of the
program on the hardware and in the simulator or synthetic target may
allow you to identify where the problems lie.</P
></LI
></UL
><P
>This approach is possible because all targets (including
simulators and synthetic ones) provide the same basic API: that
is, kernel, libc, libm, uitron, infra, and to some extent, HAL and
IO.</P
><P
>Synthetic targets are especially suitable as they allow you
to construct simulations of elaborate devices by interaction with
the host system, where an IO device API can hide the details from
the application. When switching to hardware later in the development
cycle, the IO driver is properly implemented.</P
><P
>Simulators can also do this, but it all depends on the
design and capabilities of the simulator you use. Some, like
<A
HREF="http://sources.redhat.com/sid"
TARGET="_top"
>SID</A
> or
<A
HREF="http://bochs.sourceforge.net/"
TARGET="_top"
>Bochs</A
> provide
complete hardware emulation, while others just support enough of the
instruction set to run compiled code.</P
><P
>Therefore, select a simulator or synthetic target and use
it for as long as possible for application development. That is,
configure for the selected target, build <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
>, build the application
and link with <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
>, run and debug. Repeat the latter two steps until
you are happy with it.</P
><P
>Obviously, at some time you will have to switch to the intended
target hardware, for example when adding target specific feature
support, for memory footprint/performance characterization,
and for final tuning of <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> and the application.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN511">Application Development - Target Specific Part</H2
><P
>Repeat the build-run-debug-cycle while performing final tuning
and debugging of application. Remember to disable <SPAN
CLASS="PRODUCTNAME"
>eCos</SPAN
> assertion
checking if you are testing any performance-related aspects, it can
make a big difference.</P
><P
>It may be useful to switch between this and the previous step
repeatedly through the development process; use the simulator/synthetic
target for actual development, and use the target hardware to continually
check memory footprint and performance. There should be little cost
in switching between the two targets when using two separate build
trees. </P
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