Port to Atmel AVR RISC processor

[Joel Sherrill]

David Dudley wrote:

>Has anyone attempted to port rtems to the Atmel AVR chip family?
>
>Looks like I'm going to have a requirement for one, so if no one has .... 
>well, its started.
>
>
>Got a question, or two before getting started, though:
>
>1. The "Porting" guide doesn't reflect the structure of the RTEMS directory, 
>but rather, the 'build' directory, from what I've seen.  Is there a document 
>that describes the source directory, and what goes where (and where things 
>are to start with??? )?
>  
>

Please point out those differences so they can be fixed.  The 
rearrangement of the
source tree to separate BSPs and ":CPU Kit" many not be reflected.  In 
general,
you are looking at the directories:

  cpukit/score/cpu/XXX
  c/src/lib/libcpu
  c/src/lib/libbsp

>2. How do the libbsp/libcpu directories get built into the "build" directory?  
>It appears that files are actually copied from one place to the other - 
>what/how are the files determined, and why didn't you just use symbolic 
>links?
>
I will let Ralf go on this one.  It really isn't as radically different 
as it looks though.

>
>3. in the cpukit directory, is the file structure 'reflected' into the build 
>directory somehow? ... and if so.... how?
>  
>
Ralf.

>4. What "*.ac" files need to be modified to add the new architecture into the 
>package?
>  
>
I think this is in the archives but you will have to create libbsp/avr 
and populate that.
The main ac scripts will be  rtems-cpu-subdirs.m4

>5. Is newlib support a requirement?  I now have a C compiler that efficently 
>compiles code for the processor, but there isn't any runtime support, to 
>speak of.
>  
>
RTEMS includes a lot of POSIX support.  newlib is a lot easier to use.

You can use other C libraries but not as easily.  If you stick to the 
Classic API
and no networking, the dependencies on a libc will be smaller.  I recall the
AVR is a small CPU so you might find yourself disablining certain parts of
the tree for the avr.

>
>Thanks-
>David Dudley
>  
>