Re: [avr-libc-dev] Re: Unified ELF file [was: RE: [avr-chat] Re: GUI wrapper for avrdude]

[Rick Altherr]

On Aug 30, 2007, at 12:41 AM, Erik Christiansen wrote:

> On Thu, Aug 30, 2007 at 04:55:02PM +1000, Erik Christiansen wrote:
> > On Thu, Aug 30, 2007 at 07:16:24AM +0200, Joerg Wunsch wrote:
> > > If all else fails, we could still opt for differently named input
> > > section (lfuse, hfuse, efuse), and combine them in the linker script
> > > into one output section.  Again, that would be similar to combining
> > > .eeprom* input sections into just one .eeprom output section right
> > > now.
> >
> > Actually, I think that's neater, not least because the magic  
> > addresses
> > are not seen in the assembler source, but reside only in the linker
> > script, where they belong.
>
> The attached does it more neatly, doesn't it?   :-)
>
> Erik
>
> P.S. If there's any assembler macro mucky-stuff left to do, I'm
> available. (Week after next. :-)
> <fuse_demo.s>
> <fuse_demo.ld>
> <fuse_demo.objdump>
> <fuse_demo.map>
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> AVR-libc-dev mailing list
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> http://lists.nongnu.org/mailman/listinfo/avr-libc-dev

I posted this to avr-libc-dev just a few days ago.  I'm reposting it  
to avr-chat since most of the discussion about this topic is  
happening here.

> Having had a bit of experience with the CONFIG bits in PIC  
> development, I was surprised to see that the FUSE and LOCK bits in  
> AVR weren't able to be set in the source code.  A friend and I came  
> up with the following solution:
> - Create a header file for each device that contain:
>   - A define that allocates an extra ELF section for the various  
> fuse and lock bits
>   - A set of defines that describe the various bits in the fuse and  
> lock bits
>   - A define for the default value described in the datasheet
> - A set of Makefile rules that:
>   - Extract the new ELF sections into separate hex files
>   - Invoke avrdude with commands that program the lock and fuse  
> bits with the contents of the new sections
>
> Here is an excerpt from the ATmega8's header file for HFUSE:
>
> /* High Fuse Byte */
> #define HFUSE const unsigned char hfuse __attribute__((section  
> (".hfuse")))
>
> #define BOOTRST         ~_BV(0)
> #define BOOTSZ0         ~_BV(1)
> #define BOOTSZ1         ~_BV(2)
> #define EESAVE          ~_BV(3)
> #define CKOPT           ~_BV(4)
> #define SPIEN           ~_BV(5)
> #define WDTON           ~_BV(6)
> #define RSTDISBL        ~_BV(7)
>
> #define HFUSE_DEFAULT SPIEN & BOOTSZ1 & BOOTSZ0
>
>
> The Makefile rules are a bit more complex since they are entwined  
> with a whole set of rules to reduce the amount of setup needed for  
> an AVR-based project.  I've attached an example project that shows  
> these header files and Makefile rules in use.  The use of the fuse  
> header is in example.c where LFUSE is set.  To build it, put the  
> files from the header.tar.gz into the same directory as the I/O  
> definition headers.  Then, in example.tar.gz, run 'make' to build  
> the software and 'make program' to write it to a device.  To get  
> rid of all the generated files, run 'make clean'.

headers.tar.gz
Description: GNU Zip compressed data

example.tar.gz
Description: GNU Zip compressed data

> Currently, we only have files for the ATmega8 and ATmega16.  That's  
> mainly because those are the only 2 devices we have used this  
> with.  It definitely makes keeping track of things like clock  
> configuration and watchdog timer enable easier as well as enables a  
> way for them to be included in a source repository.

--
Rick Altherr
address@hidden

"He said he hadn't had a byte in three days. I had a short, so I  
split it with him."
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