Page 204 - The Unofficial Guide to Lego Mindstorms Robots

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your source code.∗ For example, if you saved the source code above in a file called /projects/HellolegOS.cyou would edit the
Makefile's TARGET like this:

TARGET=/projects/HellolegOS

Then type make at the command line. If everything is installed corr ectly, you'll end up with a HellolegOS.srec file in the
sa me directory as the source file.

Trouble with Make

If you can't make HellolegOS.c, and you' re starting to curse at your computer, ta ke a deep
breath. legOS has a strong online community; people will help if you ask. The "Online
Resources" section of this chapter has pointers to helpful sites. One of the best things you
ca n do is look at LUGNET, http://www.lugnet.com/, and search through the discussion
group archives for the particular prob lem you're having. There are at least as many
messages about configuring t he legOS development tools as there are about actually
p rogramming in legOS.

If you're using one of the online compilers,just co py the source into the web page and press the compile button. If there are no
errors, you will get back an .srec file representing your compiled legO S program.

Regardless of how th e source file is compiled, you will then need to download th e .srec file to the RCX, using either nqc or
firmdl.

When the download is complete, your RCX will display the string "legOS" to indicate that legOS is running. To actually run
the program yo u just wrote, press the Run button. The display will show "Hello" for a second or so, then show two zeros. The
le ft number shows the result returned from our main() function. Control has now returned to legOS; you can use the On-
Off button to switch th e RCX off and on. When the RCX is on, you can press Run again to see the "Hello'' message again.
Show your friends and family; they will be awed and inspired.

Function Reference
Once you've seen one RCX development environment, you've seen them all—to some degree, at least. If you've been reading
through this book in order, you've probably noticed that NQC and pbFORTH have similar commands but different syntax.
Likewise, legOS has a set of functions that looks a lot like pbFORTH and

∗ Make sure you've edited Makefile.common. The TOOLPREFIX and LEGOS_ROOT lines should point to the appropriate
directories on your system, as described in the comments. Make sure you put a trailing slash on the LEGOS_ROOT directory.