On 3/4/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
On 3/4/07, Daniel Rozsnyó <[EMAIL PROTECTED]> 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
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