[time-nuts] OT: 10 MHz data capture, help
Tom Van Baak
tvb at LeapSecond.com
Sat Apr 25 15:11:54 UTC 2009
> There are two issues with this problem. One is clock recovery. The other is
> getting a large chunk of data into memory and presumably on to disk.
> This leads in to a question I've been meaning to ask for a while. I've been
> looking for a low cost FPGA on PCI board. This might be a wild goose chase,
> but I think it would be handy for a bunch of time-nut type applications.
Let me give you an update. First, thanks to all of you with
suggestions on my original data capture question. As John
mentioned I looked at a lot of alternatives with a special eye
towards USB 'scope and logic analyzer products, eventually
trying out the USBee SX.
I found a clock edge to go with my NRZ data so that made
my problem easier (avoiding having to oversample the data).
I was quite amazed at the performance of the USBee device.
Even on a tiny netbook PC it will stream 8-bit logic samples
at 10 MHz (24 max) with no dropouts into available memory
(which on my netbook is usually over half a gigabyte, giving
over 50 seconds of continuous capture).
I'm still working on the PC software to decode this mass of
data (maybe even in real-time) and working on longer runs,
but mostly I was pleasantly surprised how easy it is to obtain
high rates over USB2.0.
I was worried that I'd have to go with some expensive or very
complicated PCI-card based acquisition. So Hal, give USB2.0
some consideration before you settle on PCI.
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