2d2ae68175
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3988 42af7a65-404d-4744-a932-0658087f49c3
194 lines
7.0 KiB
Plaintext
194 lines
7.0 KiB
Plaintext
README
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^^^^^^
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This README file describes the contents of the build configurations available
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for the NuttX "sim" target. The sim target is a NuttX port that runs as a
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user-space program under Linux or Cygwin. It is a very "low fidelity" embedded
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system simulation: This environment does not support any kind of asynchonous
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events -- there are nothing like interrupts in this context. Therefore, there
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can be no pre-empting events.
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In order to get timed behavior, the system timer "interrupt handler" is called
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from the sim target's IDLE loop. The IDLE runs whenever there is no other task
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running. So, for example, if a task calls sleep(), then that task will suspend
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wanting for the time to elapse. If nothing else is available to run, then the
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IDLE loop runs and the timer increments, eventually re-awakening the sleeping task.
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Context switching is based on logic similar to setjmp() and longjmp().
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The sim target is used primarily as a development and test platform for new
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RTOS features. It is also of academic interest. But it has no real-world
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application that I know of.
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NOTE: In order to facility fast testing, the sim target's IDLE loop, by default,
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calls the system "interrupt handler" as fast as possible. As a result, there
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really are no noticeable delays when a task sleeps. However, the task really does
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sleep -- but the time scale is wrong. If you want behavior that is closer to
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normal timing, then you can define CONFIG_SIM_WALLTIME=y in your configuration
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file. This configuration setting will cause the sim target's IDLE loop to delay
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on each call so that the system "timer interrupt" is called at a rate approximately
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correct for the system timer tick rate. With this definition in the configuration,
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sleep() behavior is more or less normal.
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64-Bit Issues
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^^^^^^^^^^^^^
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As mentioned above, context switching is based on logic like setjmp and longjmp.
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This context switching is only available for 32-bit targets. On 64-bit machines,
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this context switching will fail.
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There are other 64-bit issues as well. For example, addresses are retained in
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32-bit unsigned integer types in a few places. On a 64-bit machine, the 32-bit
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address storage may correcupt 64-bit addressing. NOTE: This is really a bug --
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addresses should not be retained in uint32_t types but rather in uintptr_t types
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to avoid issues just like this.
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The workaround on 64-bit machines for now is to build for a 32-bit target on the
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64-bit machine. This workaround involves modifying the Make.defs file in the
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appropriate places so that -m32 is included in the CFLAGS and -m32 and -melf_386
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are included in the LDFLAGS. See the patch 0001-Quick-hacks-to-build-sim-nsh-ostest-on-x86_64-as-32-.patch
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that can be found at http://tech.groups.yahoo.com/group/nuttx/files.
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Buffered I/O Issues
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^^^^^^^^^^^^^^^^^^^
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The simulated serial driver has some odd behavior. It will stall for a long time
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on reads when the C stdio buffers are being refilled. This only effects the behavior
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of things like fgetc(). Workaround: Set CONFIG_STDIO_BUFFER_SIZE=0, suppressing
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all C buffered I/O.
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Networking Issues
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^^^^^^^^^^^^^^^^^
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I never did get networking to work on the sim target. It tries to use the tap device
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(/dev/net/tun) to emulate an Ethernet NIC, but I never got it correctly integrated
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with the NuttX networking (I probably should try using raw sockets instead).
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X11 Issues
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^^^^^^^^^^
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There is an X11-based framebuffer driver that you can use exercise the NuttX graphics
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subsystem on the simulator (see the sim/nx configuration below). This may require a
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lot of tinkering to get working, depending upon where your X11 installation stores
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libraries and header files and how it names libraries.
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For example, on UBuntu 9.09, I had to do the following to get a clean build:
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cd /usr/lib/
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sudo ln -s libXext.so.6.4.0 libXext.so
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(I also get a segmentation fault at the conclusion of the NX test -- that will need
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to get looked into as well).
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The X11 examples builds on Cygwin, but does not run. The last time I tried it,
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XOpenDisplay() aborted the program.
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Configurations
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^^^^^^^^^^^^^^
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mount
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Configures to use examples/mount. This configuration may be
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selected as follows:
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cd <nuttx-directory>/tools
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./configure.sh sim/mount
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nettest
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Configures to use examples/nettest. This configuration
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enables networking using the network TAP device. It may
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be selected via:
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cd <nuttx-directory>/tools
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./configure.sh sim/nettest
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NOTES:
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- The NuttX network is not, however, functional on the Linux TAP
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device yet.
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- As of NuttX-5.18, when built on Windows, this test does not try
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to use the TAP device (which is not available on Cygwin anyway),
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but inside will try to use the Cygwin WPCAP library. Only the
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most preliminary testing has been performed with the Cygwin WPCAP
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library, however.
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NOTE that the IP address is hard-coded in arch/sim/src/up_wpcap.c.
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You will either need to edit your configuration files to use 10.0.0.1
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on the "target" (CONFIG_EXAMPLE_NETTEST_*) or edit up_wpcap.c to
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select the IP address that you want to use.
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nsh
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Configures to use the NuttShell at examples/nsh. This configuration
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may be selected as follows:
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cd <nuttx-directory>/tools
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./configure.sh sim/nsh
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nx
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Configures to use examples/nx. This configuration may be
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selected as follows:
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cd <nuttx-directory>/tools
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./configure.sh sim/nx
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Special simulated framebuffer configuration options:
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CONFIG_SIM_X11FB - Use X11 window for framebuffer
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CONFIG_SIM_FBHEIGHT - Height of the framebuffer in pixels
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CONFIG_SIM_FBWIDTH - Width of the framebuffer in pixels.
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CONFIG_SIM_FBBPP - Pixel depth in bits
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NOTES:
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- If CONFIG_SIM_X11FB is selected then the following are
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needed
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CONFIG_SIM_FBBPP (must match the resolution of the display).
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CONFIG_FB_CMAP=y
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My system has 24-bit color, but packed into 32-bit words so
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the correct seeting of CONFIG_SIM_FBBPP is 32.
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- For whatever value of CONFIG_SIM_FBBPP is selected, then
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the corresponidng CONFIG_NX_DISABLE_*BPP setting must
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not be disabled.
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- The default in defconfig is to use a generic memory buffer
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for the framebuffer. defconfig-x11 is an example with X11
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support enabled. To use this configuration you have to
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configure as follows:
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cd tools
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./configure.sh sim/nx
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cd ..
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cp configs/sim/nx/defconfig-x11 .config
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- The default is the single-user NX implementation. To select
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the multi-user NX implementation:
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CONFG_NX_MULTIUSER=y
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CONFIG_DISABLE_MQUEUE=n
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- To get the system to compile under various X11 installations
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you may have to modify a few things. For example, in order
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to find libXext, I had to make the following change under
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Ubuntu 9.09:
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cd /usr/lib/
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sudo ln -s libXext.so.6.4.0 libXext.so
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ostest
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The "standard" NuttX examples/ostest configuration. This
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configuration may be selected as follows:
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cd <nuttx-directory>/tools
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./configure.sh sim/ostest
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pashello
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Configures to use examples/pashello. This configuration may
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by selected as follows:
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cd <nuttx-directory>/tools
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./configure.sh sim/pashello
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