If you run it over 1G fiber, you can consider using WR protocol. You don't need WR switch since it can be used as point to point. WR gives absolute 1ns of accuracy and about 15ps of jitter, over 10km fiber. Greg
-----Original Message----- From: Robert Jördens [mailto:r...@m-labs.hk] Sent: Thursday, March 31, 2016 9:55 PM To: Slichter, Daniel H. (Fed) <daniel.slich...@nist.gov> Cc: Sébastien Bourdeauducq <s...@m-labs.hk>; Grzegorz Kasprowicz <kaspr...@gmail.com>; Grzegorz Kasprowicz <gkasp...@elka.pw.edu.pl>; Leibrandt, David R. (Fed) <david.leibra...@nist.gov>; artiq@lists.m-labs.hk Subject: Re: [ARTIQ] TTL + slow DACs On Thu, Mar 31, 2016 at 7:45 PM, Slichter, Daniel H. (Fed) <daniel.slich...@nist.gov> wrote: >> Since this is another piece of hardware and the processing >> constraints as well as the electrical constraints are so different, >> it seems prudent to account for these differences. Consider doing proper >> galvanic isolation with a fiber: >> ground potential differences easily >> -- and even in well controlled labs -- exceed the common mode >> tolerances of lvds if the devices are a few tens of meters apart. >> >> This is why we would like to consider a very low barrier, non-rack >> form factor that is connected by fiber plus a simple power supply and >> provides a good number of analog voltages and a good number of ttls. >> That obsoletes the LVDS breakout board which also doesn't help with >> the galvanic isolation for the high density low speed DAC that we >> would like to bundle with that box. > > OK, fiber is superior for galvanic isolation, but at the end of the day this > would be a solution with just a few TTL lines per board, and you would then > sprinkle these around the lab, correct? And clock/timing transfer can be > done over the fiber in a suitable way? Yes. We suggest to run DRTIO over that 1 GBit/s fiber link. That way we get absolute ns-timing and a clock. TTL timing jitter would just be limited by how far we drive the "good stable low noise LO" game and then FPGA IO jitter. Same as for what we could do from within a crate. But it would be worse than the jitter from the high performance RF crate DSP AMC. TTL numbers around 16 or 32 and DAC channels around whatever AD53[67][0123] one chooses. This scattered box should be very cost efficient. _______________________________________________ ARTIQ mailing list https://ssl.serverraum.org/lists/listinfo/artiq
