[USRP-users] Ethernet over SFP+ in custom FPGA design (X3x0)

Ian Buckley ianb at ionconcepts.com
Thu Nov 9 04:15:22 EST 2017


Christian,
CHDR packets are encapsulated in UDP/IP between Host and USRP. See the attachment.

PHY+ MAC functionality live under the x300_sfpp_io_core. However these blocks do not encapsulate/decapsulate the network packets.
All the ethernet/IP/UDP framing fields are added by chdr_eth_framer on egress, and will be removed on ingress by etc_dispatch (if needed).

-Ian
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> On Nov 5, 2017, at 5:55 AM, Christian Lenz via USRP-users <usrp-users at lists.ettus.com> wrote:
> 
> Hey Sugandha,
> 
> thanks for your help. I apologize for the incredible delay from my
> side, but back to my question.
> 
> We want to port a hole IP solution from some proprietary hardware to
> the USRP and evaluate the costs (mainly development time) of migrating
> our IP to RFNoC vs. a custom image.
> The crux is, we already have a complete implementation of both FPGA
> infrastructure (mostly auto-generated VHDL) and the corresponding
> software running on a connected PC. However, on the currently used
> hardware platform, the PC is connected via USB.
> That's why I'm interested in the effort to get the Ethernet connection
> running.
> 
> 1. You wrote that eth_dispatch and chdr_eth_framer blocks handle MAC,
> IP etc., but I thought we are only talking about PHY+MAC
> implementation. So does the Ethernet Core actually implement IP layer
> too?
> 2. For the packte based communication you said that as long as it is a
> chdr paket, the FPGA would handle it. The structure of such a chdr
> paket can be found here:
> http://files.ettus.com/manual/page_rtp.html#rtp_chdr. Related to point
> 1, the chdr structure must be present in the payload of an Ethernet
> frame or is this already the (adapted) Ethernet frame structure itself?
> Do you know if i can transmit a chdr paket to the USRP utilizing a so
> called "Raw-Ethernet socket" (what seems to be a solution for
> MAC-layer Ethernet communication w/o TCP/IP). For isntance, raw
> ethernet sockets are availably in Python.
> 3. Is the code of the UHD part available that interfaces the network
> device and drops of the chdr pakets?
> 
> Thanks again,
> Christian
> 
> Zitat von Sugandha Gupta <sugandha.gupta at ettus.com>:
> 
>> Hi Christian
>> 
>> It would be good if you could explain your application and need to have a
>> custom image. From your questions, it looks like you would be redoing a lot
>> of the infrastructure already present in the X3x0. In your application, if
>> you want to add new blocks to the existing code to offload SW tasks, you
>> can use the existing RFNoC framework
>> <https://kb.ettus.com/Getting_Started_with_RFNoC_Development>.
>> 
>> See inline for the answers.
>> 
>> Let me know if you have any further questions.
>> 
>> Cheers
>> Sugandha
>> 
>> 
>> On Tue, Apr 4, 2017 at 6:54 AM, Christian Lenz via USRP-users <
>> usrp-users at lists.ettus.com> wrote:
>> 
>>> Hi,
>>> 
>>> I?m currently evaluating the effort/feasibility of running a custom FPGA
>>> image in a USRP X3x0. One thing left is the connection Host PC <?> FPGA
>>> to exchange control/status information (neither high throughput nor low
>>> latency needed here).
>>> To achieve this, I have the idea of using the provided IP to interface one
>>> of the SFP+ ports on the FPGA side and connect to a host PC using the SFP 1
>>> Gigabit Ethernet Interface Kit.
>>> Related to this are the following questions:
>>> 
>>> 1. I traced down the signals, beginning from the SFP+ FPGA pins. The main
>>> ethernet functionality (PHY+MAC) is included in the ?x300_sfpp_io_core?,
>>> correct?
>>> 
>> >> Yes.
>> 
>>> Additionally, do I need to incorporate also the ?eth_interface? included
>>> in ?x300_core/bus_int?, which somehow translates the AXI data streams
>>> coming from the ?x300_sfpp_io_core??
>>> 
>>>> The eth_interface has 2 parts
>>     - eth_dispatch - It routes the incoming packets appropriately based on
>> the MAC, IP, chdr (or not?), etc.
>>     - chdr_eth_framer -  It re-constructs the chdr packets coming back
>> from the crossbar -> adds the MAC and IP.
>>    So, I guess you would need it.
>> 
>>> 
>>> 2. I want to use the ?x300_sfpp_io_core? for a single SFP+ port with
>>> protocol ?1GbE?. I did found all the required source files except for the
>>> modules ?one_gig_eth_pcs_pma_support?, located in the ?one_gige_phy? and
>>> the ?axi64_8k_2clk_fifo?, located in the ?simple_gemac_wrapper?. There are
>>> only some references in related makefiles but I can not find the verilog
>>> source files where the modules are described in. Am I misleaded at some
>>> point?
>>> 
>>>> These files are generated during the build process.
>>     Look in :
>> <fpga-repo>/usrp3/top/x300/build-ip/<part-number>/one_gig_eth_pcs_pma_example/one_gig_eth_pcs_pma_example.srcs/sources_1/imports/example_design/support/*
>> 
>> 
>>> 3. This question may also apply to the plain UHD FPGA design: Let?s assume
>>> I get the SFP+ core running within my custom FPGA design. How do I
>>> communicate with the FPGA using an ethernet-connected host PC?
>>> 
>>>> That is what you have a existing UHD code for.
>> 
>> Since the provided cores included in ?x300_sfpp_io_core? implement PHY +
>>> MAC functionalities, do I need additional cores to implement IP and TCP/UDP
>>> or in which way do you transfer data between Host and FPGA using Ethernet
>>> (see also my question 1.)? The target would be to establish a packet based
>>> communication over Ethernet and having AXI streams for sending/receiving on
>>> the FPGA side.
>>> 
>> >> If it is a chdr packet, then the current FPGA design handles it.
>> 
>>> 
>>> Hopefully, my questions are not too far away from the oridnary USRP use
>>> case.
>>> 
>>> Thanks for the help,
>>> Christian
>>> 
>>> _______________________________________________
>>> USRP-users mailing list
>>> USRP-users at lists.ettus.com
>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>> 
>>> 
>> 
>> 
>> --
>> Sugandha Gupta
>> Staff Software Engineer
>> Ettus Research
> 
> 
> 
> 
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