[wplug] uCLinux

[Darin Ingimarson]

Weber, Larry A wrote:

>Freescale (Motorola) has recently released several new Coldfire processors (MCP523x) and an evaluation board.  I thought it might be a good learning experience to try to port uCLinux to the board. 
>
Yeah, it would definately be a learning experience for you ;-)

 From my experience in porting RTOS's (probably applicable to general 
embedded OS ports), the most frustrating part will involve setting up 
the initial cross-developmnet platfom and toolchain. This is not 
entirely trivial, and you need to make sure that your processor of 
interest is supported by your compiler. Check the GNU site for this info.

The way I would approach this project is first by answering a few questions:
- Check out toolchain support for the processor (at the very least you 
will need  gcc/gas). Has anyone built a toolchain (i.e. with precompiled 
libraries) you can download and use, or will you have to build your own?
- How close to existing, supported processors is the new one? What are 
the differences? Can you leverage existing code, binaries, or online 
docs in your project?
- What type of memory protection (if any) does the processor support? Is 
this different in any appreciable way from the existing supported 
processors. This will affect the complexity in porting the uCLinux stuff.
- Do you require any major changes to the remaining  assembler-based 
modules in uClinux (in the RT variants of Linux I have worked with this 
is mainly located in the boot and context switch code, so at least your 
problems should be confined to a relatively limited module set). If not, 
your port should be very straightforward.
- Determine the boot and storage facilities (FLASH, disk, etc) on your 
development kit and find out if you have to write any specific drivers 
to support them.
- Determine the mechanism for loading and running a binary on your dev 
kit. How difficult is it? Will you need special hardware or software 
available only under Windows? How you will load and run the very first 
binary you compile?
- Determine what the feasability for a debug (user AND kernel mode) 
connection to the dev kit is (i.e. RS-232, JTAG, etc).

If you investigate the above, I think you will get an idea as to the 
scope of project you are considering.

> I know it has been done with other versions of Coldfire processor eval. boards but this board is quite a bit different.  I just don't want to waste time on something that can't be done or would take forever to get right.
>  
>
I have no doubt that it can be done, but the "get right" part is up to 
the engineer involved ;-)

Good luck. If you have any other questions, you can email me directly if 
you like.

  -darin