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05:45 | Bertl_oO | off to bed now ... have a good one everyone!
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13:28 | namibj | The USB3 offloading seemed at least barely usable. Any idea whether it wold work with one of these: https://www.corning.com/optical-cables-by-corning/worldwide/en/products/usb-optical-cables.html ? Or something of that sort in general?
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15:54 | Bertl_zZ | changed nick to: Bertl
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15:55 | Bertl | morning folks!
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15:55 | Bertl | I'm pretty confident those active converters/extenders will work but not sure how they help except for permitting longer cable ranges
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16:00 | jhlink | What speeds are you looking at for USB3?
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16:00 | jhlink | or targeting namibj
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16:02 | jhlink | And why that cable in particular?
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16:26 | namibj | jhlink: Significantly faster than what the Axiom can/could push out via ethernet.
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16:27 | namibj | jhlink: THis cable is really light, and I'd consider it as a tether for a multicopter/hexapod, so that proper data recording can be stationary.
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16:31 | Bertl | I'd really like to know what chips they use for the conversion
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16:32 | namibj | Bertl: these ones use 5Gbit multimode fiber transceivers. Unfortunately the usb connection on the axiom isn't realized via an fpga transceiver, and can thus not easily be run over a suitable SFP/SFP+ transceiver. usb3 is quite tricky with timings and all that, so mcuh that I'd not want to try without specialized hardware like this cornings extender.
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16:33 | namibj | Bertl: if they'd not be that expensive I'd like to use one for analysis. Maybe one can get a broken cable on ebay? I understand they fake a couple hubs, likely to accumulate the allowed per-hub delay to get enough for whatever optical PHY they use for it.
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16:34 | Bertl | well, the phy is not that slow, so timing should not be a big issue
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16:34 | namibj | usb3 timing is evil.
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16:35 | Bertl | yeah, but a single hub should be allowed a way longer delay than is required
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16:35 | Bertl | anyway, what do they cost?
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16:38 | jhlink | I'm just a bit skeptical. Even if the USB3 maximum transfers speeds are 5 Gbits, would either the host or the Axiom be able to support the respective read/write operations?
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16:39 | jhlink | If the Axiom Beta runs storage of an SD card, and the maximum R/W times are less than 1 Gbits, then the bottle neck will be flash memory, not the communication protocol
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16:39 | Bertl | on the AXIOM side we can do up to 3.2Gbit/s with the USB3 plugin
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16:39 | Bertl | and there could be two of those plugins in use at the same time
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16:39 | jhlink | What about ethernet? I'm a little hazy here, but my speculation is that speeds are protocol dependent.
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16:39 | jhlink | Probably wrong, but open to corrections! :D
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16:40 | Bertl | well, we 'only' have a single 1Gbit/s ethernet connection on the Beta for now
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16:40 | Bertl | and the maximum realistic data rate there is about 800MBit/s
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16:41 | jhlink | What makes you say that?
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16:41 | namibj | Bertl: corning? 150 for 10 to 550 for 50
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16:41 | Bertl | jhlink: the tests we did run so far
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16:42 | jhlink | Goot it. :)
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16:43 | Bertl | namibj: so about 10 bucks for a cable, that's quite cheap
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16:55 | BAndiT1983|away | changed nick to: BAndiT1983
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16:57 | BAndiT1983 | changed nick to: BAndiT1983|away
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16:58 | namibj | Bertl: you mixed them up. 150 EUR for 10m, 550 EUR for 50m..... Honestly, I wish tey'd be affordable, because then I could easily test...
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17:00 | namibj | Bertl: can one push raw ethernet frames at full link rate? Like, jumbo frames, for all I care? ON a direct link there should be no packet loss anyway, and it's easy/cheap to rig a fiber link for that.
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17:00 | namibj | However, now there is food on the table. Cya
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17:12 | Bertl | namibj: ah, well, that's as expensive as expected then :)
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17:13 | Bertl | @ethernet, in theory yes, but we didn't test that yet
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17:13 | BAndiT1983|away | changed nick to: BAndiT1983
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17:13 | Bertl | still it's only 1Gbit at most
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17:15 | felix_ | iirc the hard mac in zynq7 doesn't support jumbo frames; not sure if the pins used for the phy could be rerouted to the fpga fabric instead of the hard mac
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17:15 | Bertl | yes, AFAIK they can be used from the fabric
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17:16 | felix_ | iirc someone also started an own camera design with 10g ethernet; not sure how the project was called and if it's public though
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17:17 | Bertl | 10g ethernet in a small package would be nice
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17:18 | Bertl | but I haven't seen any existing solutions yet which would be usable ...
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17:19 | felix_ | the design uses a zynq with gtps and a TLK10031
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17:27 | Bertl | interesting, that one could actually work with normal LVDS pairs as well at half the data rate
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17:29 | Bertl | the price with 20 EUR is high but not that high
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17:30 | Bertl | and the quad channel version 'only' costs 55 EUR
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17:32 | RexOrCine|away | changed nick to: RexOrCine
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17:59 | BAndiT1983 | changed nick to: BAndiT1983|away
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18:02 | namibj | Bertl: a gigabit is a gigabit ;).... There are reasons why I considered asking trenz about solding a 10ghz trensceiver version, where the only real difference would be the higher specs and a metal lid over the flip-chip, in one of their micro modules. It would have been smaller than the zynq, with 3 high-density connectors on the bottom. I decided against and went for a genesys 2, because of the higher
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18:02 | namibj | specs and lower price. It's not suitable for an axiom form factor though.
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18:03 | namibj | felix_: so let it have no jumbo support. I don't care about the measly increase in datarate, just about the lower scheduling overhead due to lower packet per second counts.
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18:04 | namibj | Bertl: you mention a theoretical feasibility to use 10g ethernet on the apertus board? Or am I missunderstanding you?
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18:09 | Bertl | well, we have two plugin slots with a total of 12 LVDS pairs capable of at least 1Gbit/s each
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18:09 | Bertl | so with the 'right' plugin 10G should be doable, at least in one direction
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18:13 | namibj | basically TE0745-02-30-2IA with the FB part swapped out for a FF part. Nice and compact, no more than 4/6 layers should be needed on the host. But as said, I didn't go for it, and I gotta ask the guy from Kron Technologies I met @camp for telling me which sub-500$ fpga board he mentioned that could handle 10G ethernet on SFP+.
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18:15 | Bertl | and that's how you ended up with the genesys 2?
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18:15 | Bertl | (because that's not sub 500$ :)
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18:16 | namibj | Bertl: yeah.... wait, this is unidirectional? Uh-oh, most transceivers afaik don't like this. But it might be possible nonetheless. Any idea for an affordable serializer to feed this though? otherwise one'd have to stick with 1G optics, and use a bundle of them with a 12-fiber cable. That would leave 2 for a return channel though, and require a switch on the remote end which you could tell to route
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18:16 | namibj | packets appropiately.
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18:17 | namibj | Bertl: I bought it last year ;). ALso I got academic discount.
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18:19 | Bertl | well, for raw unidirectional ethernet frames, you can just drop the received data
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18:19 | namibj | While I'm at this: could one theoretically transmit the sensor outputs single-ended to the fpga? So that it'd be possible to detach it to place it in the middle of a telescope tubu, with laptop-screen-edge-coax cables in a bundle for transmitting it without much optical obstruction? Or just general detached sensor?
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18:19 | Bertl | you might also make it 10G/1G bidirectional
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18:20 | Bertl | depends on the read out speed you want to achieve from the sensor
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18:20 | namibj | Bertl: it's about whether the optics themselves play with this, considering that you'd want to skip the useless fibers to stay within the cheap/light 12-fiber cables.
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18:20 | namibj | Bertl: 600MHz?
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18:21 | Bertl | the sensor can do 1 to 64 LVDS pairs for data
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18:21 | Bertl | so if you are happy with one data and one control channel
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18:21 | namibj | I know. I meant per channel. If I use it with the genesys 2, I'd try for 64.
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18:21 | Bertl | you can easily feed that through a cat 6 cable :)
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18:22 | Bertl | and at 600MHz you are probably fine for some distance
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18:22 | namibj | Oh, I am not after those distances. I mean, over like 50cm _max_.
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18:22 | Bertl | 50cm is a lot for 67 LVDS pairs
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18:27 | namibj | The cable has low loss, well, somewhat. It's a fine coax: http://www.micro-coaxial.com/wp-content/uploads/2019/01/Sumitomo-HITACHI-micro-coax-cable-assembly-factory.jpg
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18:42 | namibj | Bertl: 15 might suffice if I'd push it, assuming it's for the 400mm f/2 design from https://www.telescope-optics.net/field_flattener.htm example 1 deign point 7 (the 7is circled in).
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18:45 | namibj | This has sufficient sharpness to get 90% ensquared energy, i.e., a planar wavefront would result in 90% of the photons getting to the sensor hitting a single pixel, as long as the angle was centered.
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18:47 | namibj | This is already at the edge of the sensor, btw., with 2 degree off-axis (= 4 degree diagonal FOV).
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21:10 | se6ast1an_ | off to bed, good night
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21:17 | Bertl | nn
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23:48 | RexOrCine | changed nick to: RexOrCine|away
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