Re: question about interface..

Yea, we could find a pin-compatible Flash chip.  The problem is that a Flash chip works differently than a ROM chip - there are signals that a Flash chip needs to work correctly that a ROM chip does not.  Therefore, its a "crap-shoot" whether or not the Flash would even work on the J72x's mass-produced ROM board.  If HP didn't put down all the traces (i.e. wires) on the daughterboard to support Flash operation (IMHO very likely), you're out of luck and just broke your ROM board....  However, if you have a second board that you don't mind tearing up, the Flash parts may only be $30 or $40 each (you'll need two).  But then, how do you do the first-time Flash program?  Back to that damnable chicken-n-egg problem:  You can't program the flash *in the Jornada* without removing the ROM chips - but the ROM chips tell the Jornada how to boot and the Jornada has to be running to program the flash
 ....

Ok, program the flash before you solder the flash on the board.  Unfortunately, I don't have a programmer.  Ok, build one.  Well, we have to anyway.  Plus, what happens if we get the bootloader wrong or later on down the road we end up with a bad flash?  We've got no way to restore proper operation short of de-soldering the flash to reprogram it.  Any kind of soldering/desoldering process stresses the chips and really shouldn't be done - unless you are throwing the chips away.  Personally, I don't want to do that with a $40 part.  At this point the engineer in me cries "WAIT!" to this process and says "if we are going to go through *that* much trouble, why not just build our own board?"

Now, I really don't want to get into any kind of flame-war over this like what happened not too long ago, but many of us on this list have already been down this road already.  Its very hard to justify a ROM board modification when its not for certain that it will work and a whole new board isn't that much harder.


[email protected] wrote ..
> What I meant was this....  Find a compatable rom/flash/whatever chip to
> replace the ones on our boards...  have it point to the CF so we can boot
> whatever we want from it....
> 
> On 22 Dec 2006 at 15:28, Mark Gollahon wrote:
> 
> Hey!  Sorry for the delay in my reply - My family is getting ready for
> Christmas.
> 
> In any case, no, the Jornada 720/728 is not capable of booting from CF
> - at least, not with the WinCE bootstrapper.  Plus the ROM and RAM are
> all on the same daughterboard.  Take the daughterboard out, all the ram
> and rom is gone.  That's why it is important to put RAM and FLASH back
> on....
> 
> And, no, you're not being stupid  :)  Just a little uninformed in the details
> - no biggie.
> 
> And, yes, the StrongARM processor *could*in*theory* support more than 64Megs
> of RAM, but it is not clear how to do that from just the board schematics
> that I have.  Anyway, I was hoping to do 128/128 - but I need a bit more
> information to make that happen.  At this point the maximum that I *know*
> I can do is 64/64.  I might be able to do 64Megs RAM / 128Megs Flash (and
> I will lay the traces on the board down for that), but I won't really know
> until I actually test it.  So many unknowns - so little time....  :D
> 
> BTW, I am about 1/4 done designing the new circuit board based on HP's
> earlier flashboard design.  (However, I've been distracted with "putting
> food on the table" as it were.) Once done with it, I will need to design
> and build a programmer.  The programmer will be a bit harder as I don't
> have a reference design like I do with the flashboard.
> 
> And, no, the J720/728 cannot do its own *initial* programming as it is
> a "blank slate" until I have a bootloader like uboot or redboot initially
> flashed.  Once the bootloader is in place, then the J720/728 can do its
> own programming....
> 
> Merry Christmas and happy New Year!
> -Mark Gollahon
> 
> 
> [email protected] wrote ..
> > Just wondering....  Is the 720/728 capable of booting from the CF?
> > 
> > If it is, couldn't you design a smaller flashboard with more ram?
> > 
> > Fnd the smallest size Flash chip, put a bootloader or something on
> > it to point to the CF -- and we could use a Microdrive or a regular
> > CF card for the drive.  That would have to be easier than trying
> > the whole enchalada of adding more ram PLUS getting flash.
> > 
> > Am I being stupid?
> > 
> > Can we get 128 ram in it?  (I assume we'd have to do some commands to
> > make it recognize above 32)
> > 
> > I see that CE.net 4.2 supports the CPU in the jornada -- so It might
> be
> > possible to put a newer OS in it too...
> > 
> > _______________________________________________
> > jornada mailing list
> > [email protected]
> > https://handhelds.org/mailman/listinfo/jornada

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