On 08/29/2012 02:30 AM, Jason Manley wrote:
If you take a look at the pocket correlator design (tutorial 4), you'll find
that it does four inputs of 400MHz bandwidth (800Msps). I think it has 4-tap
PFBs with 1024 channels by default, which fits into a ROACH-1. If you forfeit
two of the inputs, you should be able to get at least twice the channel
resolution. If there's BRAM left over, you should be able to get even more.
I forgot to mention that we need a bandwidth of at least 640 MHz.
Tom
Jason
On 29 Aug 2012, at 11:19, Tom Kuiper wrote:
Thanks for that, Jason! It is very timely. The reason I went down this path
is because I have a spectrometer design, by Joseph Trinh, which takes a
slightly different approach to bram access and so I could not use the
katcp_wrapper which I'd been using with your 16K spectrometer. He'd offered to
modify it but I thought it cool to try the file access I/O. I think as a
result of this exchange, I'll ask Joseph to modify his design and I'll start
using pyro.
I hope he can squeeze it into a ROACH-1. He's got a 2x1024 spectrometer design
for me now but had to drop the PFBs because of insufficient resources. I'm
asking him to try 2x512 with PFBs. Does anyone already have something like
that?
Next time around we'll use ROACH-2 but at the time we placed the orders we
weren't sure that the support for that would evolve fast enough to meet our
deadline (next month).
Cheers
Tom
On 08/29/2012 01:09 AM, Jason Manley wrote:
On 29 Aug 2012, at 02:44, Adam Barta wrote:
You could also try an ssh port forward to the katcp port ssh -vNL
7147:roach:7147 gateway
Then use the katcp interface to read / write the registers. There is a
katcp_wrapper.py in the corr library
I would like to re-inforce this suggestion if you need SSH tunnelling through a
firewall. A general word of warning to the CASPER community, which we also
explained at the recent workshop...
MeerKAT will not be supporting filesystem-level access in future boards (quite
possibly starting with ROACH-2 already) and so, unless someone else in the
collaboration picks it up, you'll be on your own if you write custom software
to run on the PPC/BORPH because new platforms might not even run BORPH at all.
There are a number of reasons for this decision, one being that we've run into
performance limitations with BORPH, but also that it's a big overhead to port
and debug and to keep it running reliably.
The only interface supported by SKA-SA will be through KATCP. So if you start
using the KATCP interface now, you'll have a transparent upgrade path to future
boards. I'd suggest you don't worry yourself too much with the low-level
detail... this is part of what CASPER tries to abstract away to ease your life
as an instrument designer.
If you don't want to write your own KATCP interface (and who does?!), consider
using one of the existing ones. The best developed ones are in c (which
includes a command-line executable for a single-line, ipython-like interactive
experience from the shell prompt if you just want to call a shell script with a
bunch of commands), available at https://github.com/ska-sa/katcp_devel, or a
number of CASPER collaborators are using the python wrapper from corr if you
want to build a higher-level GUI application. You can find a one-page getting
started guide here: https://casper.berkeley.edu/wiki/Corr
Jason
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