[Open-graphics] PCIe know-how?

[ceriel at gmail.com]

On 3/4/07, ceriel at gmail.com <ceriel at gmail.com> wrote:
> On 3/4/07, Daniel Rozsnyó <daniel at rozsnyo.com> wrote:
> > OGP does not do PCIe (yet). Only PCI and PCI-X.
> >
> > Anyway, for your instrument I would suggest interfacing it to USB2 if
> > you can offload the processing to dsp/fpga, but that won't be under
> > $100. For such a price you can get an ADC and a PCIe interface, but then
> > you will have troubles with processing the 500+ MB/s of data in realtime
> > on the PC's CPU..
>
> Thank you for your reply!
>
> There already are some Open Hardware SDR projects which use USB for
> their interface, and indeed they cost a good bit more than I'm aiming
> for. The google ad here on Gmail for example ironicially wanting me to
> spend $500 on a USB oscilloscope... I cannot justify spending such
> amounts of money just to decode SSB modulation on shortwave radio, but
> if I can bring cheap SDR to the masses and learn a lot in the process,
> I can justify a whole lot.
>
> Indeed dealing with the data would be a problem. It would be about
> 200MB/s, and I want FFTs from 0 to 50MHz, displayed on my screen at
> 60fps. I do however think it would be doable, and if not I would
> settle for even 1MHz wide chunks at a time. My computer isn't
> particularly slow, and 3GHz P4 equiv. machines aren't uncommon these
> days.
>
> Either way, if you haven't dealt with PCIe yet, the very least I can
> do is tell you what I've learned so far:
>
> It appears Xilinx is making an effort for PCIe and have some solutions
> available already. I do however doubt that their solutions are Open
> Source, so we might have to code for the protocol in the FPGA. Once
> that is done, apparently all one does is send the data to a so-called
> PHY chip for PCIe. The PHY handles the talking over the copper. TI has
> one for $7.
> The whitepapers for PCIe are copyrighted by the PCI-SIG cabal, and
> they are demanding offerings of $3000 to send them to you. However, a
> book by Addison Wesley called  "PCI Express System Architecture" costs
> $30 in e-book format.
>
> The PCIe protocol describes a serial data link over which packets are
> sent. The data field in the packet is 4kB large. Headers are about 2%
> as large, but every byte is padded with two bits to ensure that there
> never is such a long string of 1s or 0s that the clock would lose
> track of how many 1s or 0s have passed.
>
> If anyone starts working with this stuff, please contact me! =)
>
> Thank you for reading,
>
> Sincerely
> --
> Nos

Seems I sent the reply directly to Daniel instead of the list.

Since writing this I've found out that there will be a SDR project
associated with GNU Radio that will use Gigabit Ethernet, and I've
decided to try to fit the data I want over that interconnect instead
of PCIe.

-- 
Nos