David Summers wrote:

I am starting a new project where I need to have a flash file system
and an ethenet interface (HTTP and FTP).  The project is a solar
physics experiment that will be launched on a sub-orbital rocket
flight this fall.  The idea is that the experiment will write data
files to the flash file system while in flight, and then I can
download the data using ethernet after the experiment returns to
earth.

I think that Linux is the way to go for this project because of the
JFFS2 filesystem and the strong networking support.  The only problem
is that I am totally new to embedded linux.

Add Das U-Boot to your list as well!

I am prototyping my system on an Avnet FX12 development board ( Specs
here: http://tinyurl.com/4gfdv ) which is pretty similar to the Xilinx
ML403 board except with less memory and no SystemACE slot.

Interesting dev board. What is the low volume price/power consumption
is for the Virtex-4?

I will eventually build my own custom board with the same Xilinx
Virtex 4 FX12 FPGA and additional flash memory and some custom
interface hardware. My background is primarily as a hardware designer,
and I am very confortable with the FPGA part of this project.   I am
comfortable as a Linux user, and I am a pretty good C coder (for a
hardware guy anyway :).  I have never built a linux system (embedded
or desktop) before, and I need some help getting started with embedded
linux.

The ML403 is a PPC core, JTAG/COP with Xilinx gates around it, right? Then what
are your plans for the rest of the SOC? DRAM controller, local bus for Flash, FEC,
PHY controller internal or external, timers, GPIO, Bestcom DMA?

If you are a C coder then I assume you would use Verilog I hope....VHDL is for
ADA programmers!

I have already found the following websites which have been a big help so far:

http://www.klingauf.de/v2p/index.phtml
http://splish.ee.byu.edu/projects/LinuxFPGA/configuring.htm
http://www.crhc.uiuc.edu/IMPACT/gsrc/hardwarelab/docs/kernel-HOWTO.html#toc1

I have a few questions that I hope someone can help me with:

1. What is the best linux distribution to start out with?  I am
currently working with the 2.4 kernel code from
ppc.bkbits.net/linuxppc_2_4_devel, but I'm not sure that this version
be being updated.  (MontaVista also seems to be making it rather
difficult to download their free Linux Preview Kit, so I wouldn't mind
finding another distribution)    Does the DENX distribution have good
PPC support?  Are there any others that I should look at, or should I
just download the kernel source directly from kernel.org?

I am pleased with the DENX distribution todate for support of MPC5200, which
is a low power PPC based SOC. The cross-compile and userland support is
also part of this distribution.

2. kernel 2.4 or 2.6?

It is my understanding that the latest version of MTD and JFFS2 have
dropped support for kernel 2.4.  I would like to use JFFS2 on a NAND
flash device, so it seems like I should use 2.6.  (Can I use JFFS2 on
a NAND device with kernel v 2.4?)

I had some trouble with MTD/JFFS2 until a switched to the cvs version of
linuxppc_2_4_devel which added a few additional flash parts and is
working well for me under 2.4.

I think 2.6 is still pretty much bleeding edge for embedded work, IMHO.

Being a complete newbie, am I biting off more that I can handle by
trying to use 2.6?

I have been lurking on the mailing list for a while, and I know that
there are several people working on 2.6.x patches for the Xilinx
virtex 4 parts.  Could someone point me to a list of the patches that
I need to get me started?  I think that the ML403 patches should work
with my board, but I don't know which ones I need to download.


Thank you for your help,

David Summers
University of Colorado

Go RAMS!

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