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Custom Application Directories

Most people use the generic apps/ directory with NuttX. That is convenient and well-documented. However, it should always be remembered that NuttX is a stand-alone general purpose OS and has no dependency on that "canned" application directory.

This Wiki page will show you how to create your own, custom application directory from scratch.

Creating the Custom Application Directory

I created a directory to demonstrate the simplest possible custom application directory. It contains only the minimum three files: Makefile, Kconfig, and hello.c

Makefile

The custom application directory must include a Makefile and this makefile must all of the make targets expected by the NuttX build and must generate an archive called libapps.a in the top-level of the custom directory structure. The Makefile has just those minimum required targets:

...

    
    # files
    
    CSRCS = hello.c
    COBJS = hello.o
    
    ROOTDEPPATH = --dep-path .
    
    # Build targets
    
    all: libapps.a
    .PHONY: dirlinks context preconfig depend clean clean_context distclean
    .PRECIOUS: libapps$(LIBEXT)
    
    # Compile C Files
    
    $(COBJS): %$(OBJEXT): %.c
    	$(call COMPILE, $<, $@)
    
    # Add object files to the apps archive
    
    libapps.a: $(COBJS)
    	$(call ARCHIVE, libapps.a, $(COBJS))
    
    # Create directory links
    
    dirlinks:
    
    # Setup any special pre-build context
    
    context:
    
    # Setup any special pre-configuration context
    
    preconfig:
    
    # Make the dependency file, Make.deps
    
    depend: Makefile $(CSRCS)
    	$(Q) $(MKDEP) $(ROOTDEPPATH) "$(CC)" -- $(CFLAGS) -- $(SRCS) >Make.dep
    
    # Clean the results of the last build
    
    clean:
    	$(call CLEAN)
    
    # Remove the build context and directory links
    
    clean_context:
    
    # Restore the directory to its original state
    
    distclean: clean clean_context
    	$(call DELFILE, Make.dep)
    
    # Include dependencies
        

1. include Make.dep

Kconfig

A Kconfig file must be included but need not be populated with any meaningful options. This is a place where you can add settings to generate customized builds of your custom application. In the minimum case, Kconfig is only:

    # For a description of the syntax of this configuration file,
    # see the file kconfig-language.txt in the NuttX tools repository.
    #

hello.c

And, of course, you custom application must actually compile some source files in order to generate the required libapps.a archive. One of these source files must include the main() entry point to the application. The function of this main() entry point simply to bring-up the full application. It is called at the completion of OS initialization.

...

    #include <stdio.h>
    
    int custom_main(int argc, char *argv[])
    {
      printf("Hello, World!!\n");
      return 0;
    }

Building with the Custom Application Directory

In order to build with the new custom configuration, you will need the following in your configuration.

...