Hi John, I'll throw out a possibility. Perhaps the cabling isn't correct and you're only getting connectivity on one of the two wires in the differential pair. This would work *sometimes*, which is about what you're seeing.
This might happen if you wired your own cables or connectors and laid them out logically. Cat5 connectors have an unusual pinout that's not exactly logical. (At least not logical to me.) Regards, Ross On Tue, Feb 18, 2020, 5:47 PM John Ford <jmfor...@gmail.com> wrote: > > > I did some more testing, and I wanted to share the results. I have done > reverse loopback testing, sending the packets from the host to the PHY, > where it loops back inside the PHY, and is returned to the host. This > shows packet loss on the order of the total packets being lost. So this > bit of information leads me back to the analog side of things. Power > supply? oscillator? PCB layout? Our board house did 100 ohm > differential, and tested it, and it is better than 10%. The traces in the > pairs are matched to a couple of mils. Here's a drawing of the testing > that's been done first the digital and analog forwarded loopback, then the > reverse loopback. > > > > On Fri, Feb 14, 2020 at 12:52 AM Henno Kriel <he...@ska.ac.za> wrote: > >> Hi John, >> >> I have a few questions / remarks / suggestions: >> >> Do you observer CRC errors in both directions or is it only from FPGA to >> PC? >> >> In RGMII, the TX and RX clocks are not synced, but in loopback mode it >> is, which might point to a metastability issue when you connect to the PC. >> >> Is the PCB a custom board or a DEV-KIT? The length matching of the traces >> is important, but the TX clock skew to the PHY is also important, since DDR >> is used. >> >> Best, >> HK >> >> On Thu, Feb 13, 2020 at 11:50 PM John Ford <jmfor...@gmail.com> wrote: >> >>> Hi all. >>> >>> I'm designing an FPGA based instrument control system with a gigabit >>> Ethernet port. It should be easy to make this work, but alas, it's giving >>> me fits. >>> >>> I have a Xilinx Artix-7 FPGA on the board, driving a TI PHY using the >>> RGMII interface from the Xilinx tri-mode Ethernet MAC core. It mostly >>> works, but not completely reliably. >>> >>> If I setup the PHY in analog loopback mode, which loops the packets back >>> to the FPGA, I can run packets at full line rate all day with no errors. >>> So I'm somewhat convinced that the RGMII link is good between the FPGA and >>> the PHY. >>> >>> If I link the board up to a computer (I've tried a couple different >>> ones,) I get ~5 to 10% of the packets being received with CRC errors. >>> >>> Is there anyone on the list that's designed Gigabit Ethernet hardware >>> that could give me a hand with this? Any ideas that jump out? I've run >>> our of ideas. >>> >>> Thanks for any advice. If you are or know a good Gigabit Ethernet guru >>> for hire, let me know! >>> >>> John >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "casper@lists.berkeley.edu" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to casper+unsubscr...@lists.berkeley.edu. >>> To view this discussion on the web visit >>> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CABmH8B-suUrcdbRYvUpCqF5NuqSE8mboYxFcGj0Mv%3DGMjDoVcQ%40mail.gmail.com >>> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CABmH8B-suUrcdbRYvUpCqF5NuqSE8mboYxFcGj0Mv%3DGMjDoVcQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "casper@lists.berkeley.edu" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to casper+unsubscr...@lists.berkeley.edu. >> To view this discussion on the web visit >> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAOjx93idJY1qjbN7HNcJuwPeTz5uFz5%3Dr64eaG3cnyBdd6DU1w%40mail.gmail.com >> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAOjx93idJY1qjbN7HNcJuwPeTz5uFz5%3Dr64eaG3cnyBdd6DU1w%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups " > casper@lists.berkeley.edu" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to casper+unsubscr...@lists.berkeley.edu. > To view this discussion on the web visit > https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CABmH8B9%2BnfqPmG-zsjj%2BPTuz5PHD3ZqnjGytUP6N%2BYRZOktvig%40mail.gmail.com > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CABmH8B9%2BnfqPmG-zsjj%2BPTuz5PHD3ZqnjGytUP6N%2BYRZOktvig%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "casper@lists.berkeley.edu" group. To unsubscribe from this group and stop receiving emails from it, send an email to casper+unsubscr...@lists.berkeley.edu. To view this discussion on the web visit https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAG4nf73E7ObLJ_khOL_sD8xVK_SEy%3D2ETD7KEuCYXBp-To5WVA%40mail.gmail.com.
