John,

I might have missed something, but if you need a FIFO size of 8K x 48Bits
you'll get that into most reasonable sixed FPGAs these days (Cyclones or
Spartans). Otherwise hang a DRAM off it as rickman says.

If your data rate to the FPGA is only 1MByte/second you could almost get
away with one of the FTDI USB 1.1 interfaces  (FT245R gives an 8 bit
fifo output).

If this isn't sufficient there are a couple of easy to implement microcontrollers
about that give you a FIFO interface at USB 2.0 full speed data rates.

The host PC would need to do more of the work but if this is acceptable then
an embedded SBC seems like complete overkill?


Nial. 

Nial Stewart wrote:
> ...
> If your data rate to the FPGA is only 1MByte/second you could almost get
> away with one of the FTDI USB 1.1 interfaces  (FT245R gives an 8 bit
> fifo output).

If the data rate is only a 1-2 Mbytes/S it can be done in a single
MPC5200,
with some (64M, 128M?) DDRAM and a flash chip. The FIFOs are on chip,
one of the serial ports can be set to do 16 or 32 MbpS; it will only
have to be
deserialized - some CPLD or whatever (6 x 74hct164....?). The entire
BOM
would be $50 to $100 for prototype quantities. With DPS running on it,
net access over the 100 Mbps Ethernet port is there. Want a HDD,
connect
one to the 5200 ATA port.
 But this is me, the rest of the world seems to consider designs which
do not rely on some intel/linux/MS monstrosity illegal nowadays.

Dimiter

P.S. a similar (doing apr. 1.8 Mbytes/S thing) is at
http://tgi-sci.com/y2demo/

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/

Original message: http://groups.google.com/group/comp.arch.embedded/msg/f06c1735c181b6cb?dmode=source

"Didi" <d...@tgi-sci.com> wrote in message 
news:e...@q10g2000prf.googlegroups.com...
> But this is me, the rest of the world seems to consider designs which
> do not rely on some intel/linux/MS monstrosity illegal nowadays.

It's just that finding people to code on those platforms is easier and -- if 
you need the complexity of a GUI or full TCP/IP stack or USB host anyway, 
there's a huge amount of code, completely free, that you can leverage if you 
just "tow the company line" and use one of those "monostrosities." A couple 
bucks extra in hardware is a lot easier to get funded than a few more 
programmers and another year of development time, after all (especially when 
finding GOOD programmers is somewhat tricky these days!)

I bet plenty of people ask why your software doesn't "look" like standard 
Windows, don't they?

Joel Koltner wrote:
> "Didi" <d...@tgi-sci.com> wrote in message
> ...
> > But this is me, the rest of the world seems to consider designs which
> > do not rely on some intel/linux/MS monstrosity illegal nowadays.
>
> It's just that finding people to code on those platforms is easier and -- if
> you need the complexity of a GUI or full TCP/IP stack
> ....

you get that under DPS as well - with a lot of functionality as a
bonus and
with a few uS worstcase IRQ latency (try *that* on the wintel things).
More, it fits it in a fraction of the flash space the wintelinux
alternatives
take.

> I bet plenty of people ask why your software doesn't "look" like standard
> Windows, don't they?

Actually they typically think this is windows runing underneath on the
first
sight...

As for programmers interfacing to this or that system the overhead is
negligible if you will use DPS. For this particular application -
moving
data from a tcp connection into some fifoed hardware - the job to do
on behalf of DPS can be explained in a message shorther than this one.

So it is all about plain human nature - practiclly all people I know
are
too scared to make a step aside of the known path, it takes some
threat to their existance to venture that. It does not matter how
tempting
those nice things under that tree look, danger may be lurking around
if
the place is so desolated.... :-).

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/

Original message: http://groups.google.com/group/comp.arch.embedded/msg/0a16cc12dffb1ba5?dmode=source

"Didi" <d...@tgi-sci.com> wrote in message 
news:f...@p25g2000pri.googlegroups.com...
> you get that under DPS as well - with a lot of functionality as a
> bonus and
> with a few uS worstcase IRQ latency (try *that* on the wintel things).

Sure, it's just that for anyone with DPS experience (where's their web site, 
btw?) you'll probably find at least 100 people with Windows or Linux 
experience.

> Actually they typically think this is windows runing underneath on the
> first
> sight...

My first guess would have been DOS with an extender. :-)

> So it is all about plain human nature - practiclly all people I know
> are
> too scared to make a step aside of the known path, it takes some
> threat to their existance to venture that.

With most people, yes, this is absolutely true.  Businesses as an entity are 
the same way -- they'll keep using crappy tools that are well-known to them 
because the thought of changing to something else just looks too risky... and 
no one wants to be the fall guy if it turns out their evaluation of the 
alternatives were wrong.

---Joel

Joel Koltner wrote:
> ...
> > you get that under DPS as well - with a lot of functionality as a
> > bonus and
> > with a few uS worstcase IRQ latency (try *that* on the wintel things).
>
> Sure, it's just that for anyone with DPS experience (where's their web site,
> btw?) you'll probably find at least 100 people with Windows or Linux
> experience.

DPS is less popular than that. It is all my work, my property etc.
Comes
on my products. I have been wanting to put a cheap product with it on
the market but I just got a setback and may be unable to do it this
year
yet again....

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/

Original message: http://groups.google.com/group/comp.arch.embedded/msg/6911f3aa16da2c35?dmode=source

Hi Didi,

"Didi" <d...@tgi-sci.com> wrote in message 
news:0...@1g2000prf.googlegroups.com...
> DPS is less popular than that. It is all my work, my property etc.

You wrote the TCP/IP stack from scratch?  That's a lot of effort!  Good work.

> Comes
> on my products. I have been wanting to put a cheap product with it on
> the market but I just got a setback and may be unable to do it this
> year
> yet again....

I hope you'll be able to do it eventually; I'm sure many people would be 
interested.

---Joel

Joel Koltner wrote:
> Hi Didi,
>
> ....
> > DPS is less popular than that. It is all my work, my property etc.
>
> You wrote the TCP/IP stack from scratch?  That's a lot of effort!  Good work.

Thanks. It took me about 6 months to do (including the DNS and some
high
level clients), and is not such a great part of DPS (about 10%).

>
> I hope you'll be able to do it eventually; I'm sure many people would be
> interested.

So do I hope  (hope, that is)! ... :-). I will eventually, it won't
take that much - I
know I'll do it, as for those interested I wish I knew a bit
more.... :-).

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/

Original message: http://groups.google.com/group/comp.arch.embedded/msg/4ccece298795c6b8?dmode=source

In article <fd9dc69f-eb74-45d8-820e-
5...@p25g2000pri.googlegroups.com>, Didi says...
> It does not matter how  tempting
> those nice things under that tree look, danger may be lurking around
> if the place is so desolated.... :-).

If the place is so desoloated it is dangerous.  Such places are away 
from support.  Also there is extra danger on first approach since the 
hazards are unfamiliar.

I rather suspect many in this group prefer the hazards and beauties of 
the new, unfamiliar (and desolate) to the dangers of the crowds.  If 
nothing else for the thrill of treading less travelled paths. 

Is the metaphor broken yet :)

Robert
** Posted from http://www.teranews.com **

On Sat, 12 Apr 2008 09:38:30 -0700, John Larkin wrote:
[re "box that will control a scientific gadget" possibly using "an 
Intel-cpu SBC and a custom board" where "SBC would talk gigabit 
ethernet to the customer's system and PCI to our board." with SBC 
like http://us.kontron.com/index.php?id=226&cat=527&productid=1726

> Our board would have a PCI interface driving a biggish FIFO, say 8k deep
> by 48 bits wide, inside an FPGA. [...]
> OK, we finally get to a question: If we run some flavor of Linux on the
> SBC, what's a good strategy for keeping the fifo loaded? Assuming that
> we have the recipe for an entire experimental shot in program ram, some
> tens of megabytes maybe, we could...
...
> 3. Best, if possible: set up a single DMA transfer to do the entire
> shot. That involves a dma controller that understands that the target is
> sometimes busy [...]

If the linux kernel is given a "mem=n" parameter at boot time, it will use 
only n bytes of memory, which leaves the balance of memory to be contiguously
allocated later with "dmabuf = ioremap(...)" (see "Allocating the DMA Buffer"
and "Do-it-yourself allocation" in Chap. 13 of Linux Device Drivers, by 
Rubini and Corbet; eg http://www.xml.com/ldd/chapter/book/ch13.html .)  

If high memory isn't usable by the DMA controller, you could build a 
kernel with your device driver using preallocated fixed buffers,
rather than loading the driver as a module.  

User code can access the buffer as a memory-mapped file; see
eg http://www.scs.ch/~frey/linux/memorymap.html for background, and see
eg http://linux.die.net/man/2/mmap for notes on some flags that can lock 
the mapped pages in memory, make them private, map to fixed location, etc.

> 4. If it's a dual-core cpu, is it hard (under Linux) to assign one cpu
> to just do the fifo transfers?
 
Root can use cpusets, described at http://lwn.net/Articles/127936/ 
to allocate cpu's and memory nodes, or can use system calls as 
described in http://linux.die.net/man/2/sched_setaffinity to 
control which cpu's given processes will run on.