Re: [jornada] Jornada 7xx Flashboard

Wow, seems I've hit upon something.... See my comments embedded in the message.

-Mark Gollahon

Sebastian Hesselbarth <sebastian.hesselbarth_at_stud.uni-hannover.de> wrote ..
> Mark Gollahon wrote:
> > Hello, all!
> > I am new to this board (as my Jornada 720 is still on its way),
> > but I have every intention of running Linux on it. Since I am
> > somewhat of a hardware tinkerer and I noticed some of you talking
> > about the flashboard, I was wondering how many of you would like
> > to have one? I might be able to kickstart the process and get
> > some if there is enough of a demand.
>
> I got a board without any parts a while ago from HP and soldered
> (nearly) all parts on it. I am missing two of the 56pF caps but had
> no time to buy them because I am working on my diploma thesis.
> Right after finishing the board the next problem will be the initial
> flash procedure because the j720 does not have (or at least no one
> ever found one) jtag interface.

First off, you have my good wishes for you on your thesis!

Also, you have hit upon the very procedure that I am wondering how to
do - the initial flash procedure. That's why I came up with the idea
of putting a CF card in place of the StrataFlash - we have card
readers that can do that!! I initially wanted to use an SD/MMC card,
but I have been unable to find a suitable controller chip that can
"map" the SD/MMC flash memory into the StrongARM's memory map (see
below for more technical info on this...).

> > Also, I have some other questions for you in relation to the
> > flashboard. For those of you that have "taken the cover off"
> > your Jornada 7xx, is there enough room in there to put in a CF
> > card? (Note: NOT in the CF slot....)
>
> Where do you want to interface the cf inside the jornada ? the sa1100's
> companion chip provides two pcmcia "slots" where one is used for the
> real pcmcia slot and the other one is connected to the cf slot (AFAIK!)
> I think connecting the flash chips from CF cards _directly_ on the data
> bus is impossible since those flash chips are _very_ different from e.g.
> strata flashes!

The daughtercard would *be* the CF interface.... For those of you
not inclined to listen to a technical discussion of this, you can
skip over the next few paragraphs....

Ok, for those of you left, here's the issue: the CF memory spec
lists several modes that the CF memory card can operate in. The
first mode that *everyone* is familiar with is the standard
PCMCIA mode. Plug it into a PCMCIA controller, voila! Off and
running. Another mode is called "True IDE". This mode allows for
hanging the CF card right off of your IDE bus like a regular
run-of-the-mill hard drive (see the various IDE->CF sockets sold
around the 'net). Another mode is "memory mapped". This is where
a microprocessor or microcontroller can "directly" address memory
in the CF card. I say "directly" because the CF card's controller
chip handles all of the different modes instead of the raw flash
memory being available right on the processor's bus (like with
StrataFlash). This is why CF memory is so flexible.

However, CF memory is also very, very sllllooooowwwwww. Because
that controller chip is in the way, read access are probably 2x or
3x slower than the StrataFlash chips. So, we give up speedy access
on bootup, but we gain a HUGE ease-of-use: we can pop out the CF
card, write different bits into it, and pop it back in - we just
upgraded our OS!

Now, I am sure that a lot of you are suddenly saying "WAIT! Slow!!
This thing is already TOO slow!!!" The only time the 720 would be
reading from the CF card is during bootup to move and uncompress
the kernel into RAM and during program startup when it is moving
the program into RAM to run.... Once everything is in memory, the
720 doesn't need to access the CF card any more and the whole
system will be like on your desktop machine.

Finally, the StrongARM can address up to 4GB of memory (i.e. it has
a 32-bit address bus). No, we can't *use* the whole 4GB, as the
chip designers at Intel decided to "split" that 4GB space into
different "areas". One area is for flash (it is 256Megs), another
area is for RAM (it is 256Megs as well), and yet another area is for
device I/O (say, to a PCMCIA controller, sound chip, or video buffer).

Granted, my explanation here is a bit simplistic, but you get the idea.

My problem is, is there enough room where the daughercard sits in
the machine to handle a CF card. I'm not worried about length or
width, I am worried about height. Is there at least the thickness
of a CF card between the CF socket below the daugthercard and the
keyboard above the daughtercard? If so, my idea will work. If not,
well, shelve it until we can build our own *motherboards* for the
720 (now, isn't THAT an idea!!!).

> > I could possibly ditch the Intel Strataflash chips on the
> > original flashboard and substitute a CF card - but I don't know
> > if there is enough room....
> > Doing this would make it MUCH easier to flash new bits into it....
>
> As I said earlier: do not try to replace the strata flashes with flashes
> from CF cards! I opened a CF card and it contained a 8bit flash and a
> ide2flash interface chip to translate ide transfers from CF slot to
> flash commands. Maybe I could have a look at my notes again because all
> I write now is taken from my mind and may be vague.
> I have some pictures of my opened joranda too but first have to search
> them on my harddisk ;)

Well, don't look at the physical product, look at the spec sheets....
I think it would work wonderfully, especially with the faster flash
memories. Read times of some of the newer CF cards out there actually
approach the read times of the original StrataFlash chips used in the
original 720 daughtercards. So, we could end up with speed as well as
ease-of-use....

> > Finally, what about memory? I noticed in the engineering docs
> > that the StrongARM could possibly host up to 256Megs of SDRAM.
> > Any out there wanting that much?? ;)
>
> I guess that would be nice but first try to get some SRAMs that are pin
> compatible ;) most newer chips are definitely _not_ pin compatible
> because they have balls only (BGA!)

Actually, the StrongARM wants SDRAM - but that is beside the point.
If a fab house is making these, who cares if the chips used are JSOP
or BGAs? Granted, the Gerber plots will have to be completely redone,
and my prototype boards could use JSOP (BTW, that's one form of
surface-mount chips...) so that I can prototype the boards at home.
(Really, as long as the parts are on only *one* side of the board,
surface mounting isn't that difficult....) I just have to find a PC
board manufacturer - I *really* don't want to trace 1mm lines all
over the dang place - I'm blind enough as it is....

So, any PCB manufacturers out there willing to give this a go?

> No, really .. linux port for joranda720 is missing _much_ parts .. at
> least for 2.6-series there is no framebuffer support and surely other
> things too (pm, pcmcia?) .. there is a 2.4-series kernel that should
> implement fb,pm and so on but i never tested it.

I thought the 2.6 kernel had power mgm't up to the point where the 720
could suspend and resume. Somebody correct me if I am not right....
Anyway, that is exactly why I think this might work well - with flash
capability, we might be able to re-jumpstart Linux development on the
720 and finally get it to where some of the other handhelds are. I am
already contemplating an OpenEmbedded (http://www.openembedded.org)
profile for the 720....

> Before you (we!?) try to design new replacement boards we should port
> framebuffer support to 2.6 (the patch was rejected by rmk, because of
> bad coding style AFAIR .. whatever that means)

Hey, I'm a hardware tinkerer and this is actually quite a simple project
(well, in theory, anyway). Take an Address and Data bus and hook it to
a CF card and some SD memory - piece of cake!

>
> > Let me know!
> > -Mark Gollahon
>
> bye, Sebastian
Received on Wed Sep 01 2004 - 19:52:55 EDT