On 03/03/2016 11:10 AM, Simon Olvhammar wrote:
Ok thanks, so it's a limit in the RFNoC software and not related to
Ettus FPGA hardware or something like that?
I dont see that limit in regular GNURadio and 8192 channels works
fine, isnt the packet size also max 9000 there?
Simon
Martin/Jonathan could comment on FPGA limits--I don't think anything
larger than 2048 is actually implemented, but I don't see
what one couldn't internally compute a larger FFT in the FPGA, being
careful to consider resources.
In regular GNU Radio, FFTs are being computed on the host PC, there's no
packet-size limitation. The limit in RFNOC is due to the
way data are packetized between the X310 and the host PC. Since
there's no current mechanism for splitting FFTs across multiple
VITA frames, you're limited to what you can do in a single
ethernet-layer frame.
On Thu, Mar 3, 2016 at 3:45 PM, Marcus D. Leech <mle...@ripnet.com
<mailto:mle...@ripnet.com>> wrote:
On 03/03/2016 05:21 AM, Simon Olvhammar wrote:
Hi,
I'm wondering what it would take to modify the current FFT
RFNoC block to be able to compute a 8192 channel FFT. Someone
that can guide me in the right direction? I'm a quite
experienced programmer, however not in HDL.
Best regards
Simon
The main current stumbling block to large FFTs in RFNOC is that
the FFT output has to be able to fit into a single transport
packet, and
that is limited to 9000 bytes, which pretty-much limits you to
2048-bin FFTs. There will be work in the future to allow FFT
outputs in
RFNOC to span multiple packets.
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