Show HN: SatCat5, the open-source FPGA Ethernet switch

https://github.com/the-aerospace-corporation/satcat5/blob/main/doc/FAQ.md

by ooterness • 2 years ago

190 30 2 years ago

We've just launched v2.5 of SatCat5, the open-source FPGA Ethernet switch [1]. SatCat5 contains various FPGA building blocks that let you build a custom mixed-media Ethernet switch. It was originally intended for cubesats [2] but has many other potential applications.

The headline feature for this release is support for the IEEE-1588 Precision Time Protocol (PTP). SatCat5 has demonstrated end-to-end synchronization to within 50 ps-rms, which is approaching the world-leading performance of CERN's White Rabbit Project [3]. Except we're doing time-transfer over regular, non-synchronous Ethernet. The key breakthrough is a new technology for digital timestamps that we've published in IEEE Access [4].

This project was featured on HN back in 2023 [5]. Since then, we've changed to the CERN-OHL-W v2.0 license, which has much better legal clarity for FPGA projects.

[1] https://github.com/the-aerospace-corporation/satcat5 [2] https://digitalcommons.usu.edu/smallsat/2020/all2020/174/ [3] https://white-rabbit.web.cern.ch/documents/White_Rabbit-a_PT... [4] https://ieeexplore.ieee.org/abstract/document/10367970 [5] https://news.ycombinator.com/item?id=34817550

minetest2048• 2 years ago

Hi!

I'm one of the engineers working with cubesat hardware and software integration, and I've been following this project since 2023 because I agree that standardizing over Ethernet over (twisted pair, UART, single pair, etc...) will solve a lot of integration pain from all of the DIY protocols that the cubesat/smallsat community uses

Some thoughts:

- You actually have a publicly available ICD at https://github.com/the-aerospace-corporation/satcat5/tree/ma... , please publicize this more in the readme! You're a very rare exception in a world of contact us and sign an NDA first and commercial in confidence ICDs, which is great, and leads me to my next point:

- Compared to HTTP API documentation, space ICDs sucks. One of the ICDs that I have put its protocol documentation as screenshots instead of copy pasteable text. Of course ICDs sucks because you won't know its quality until you buy it... Anyway standardizing on ethernet for transport layer give you all the tooling at 99% of the world's computer use, and it might be a first step in making a OpenAPI / Swagger type tool but for space protocols

- Any plans for 10base-T1S single pair ethernet? Our 6U cubesats barely have enough power to run its payload computers, let alone a FPGA based switch. But in a way a switched star network can be more reliable than a multidrop bus, as you can isolate babbling idiot nodes, and filter out accidental/intentional MAC/IP address spoofing

ooterness8• 2 years ago

Thanks for a very thoughtful reply!

Regarding the Slingshot ICD: Noted, I'll make a point to update the readme. That document is literally the payload ICD for the Slingshot-1 cubesat that launched in July 2022 [1][2]. Future missions may take things in a slightly different direction, but that ICD is a flight-proven point design that shows what's possible. The space industry's NDA-by-default attitude definitely creates a lot of unnecessary friction.

I totally agree that off-the-shelf tooling is a huge benefit of leaning into Ethernet. In particular, Wireshark has been essential in winning over hesitant developers; it's just light-years ahead of what you usually get for debugging microcontrollers.

I've been watching the various 10BASE-T1S / 100BASE-T1 / 1000BASE-T1 standards, but company interest has been limited. AFAIK none of them can be attached directly to FPGA GPIO/SERDES/etc., so you need a separate PHY chip on both ends of the link. For us, the competition is SGMII over coax (for FPGA payloads) or SPI/UART over 4 wires (for microcontroller payloads). Cubesat cable runs are so short that the ability to directly attach to GPIO typically outweighs potential size and weight savings in the cable harness, plus it's one less chip with unknown radiation tolerance, etc.

That said, the good news is that -T1 PHYs typically have one of the usual *MII options (RMII, SGMII, etc.), so many are already compatible with SatCat5. The bad news is 10BASE-T1S requires CS/MA and PLCA logic that is not yet supported. (But if anyone wants to contribute cool features to this open source project, please reach out.)

[1] https://aerospace.org/sites/default/files/2022-08/Slingshot_... [2] https://aerospace.org/article/aerospaces-slingshot-1-demonst...

johnwalkr2• 2 years ago

Great work on this, it looks really promising! The industry is really a mess with a mix of interfaces. On one end there is stuff like RS422 which is simple but only the hardware layer is really standard and normally its not set up or tested to more than 1Mbps. On the other end there is stuff like spacewire which is a good standard but it's not something a university payload team can dive into with COTS parts.

Question: what's the power consumption like? When I was an aerospace grad student, I tried really hard to use ethernet to interface everything for a cubesat-sized spacecraft. But it turned out each port consumes about 0.25W at 10Mbps and 0.5W at 100Mbps. That's per port, so up to 1W just to connect 2 devices. That is a lot when your main cpu consumes 1W, and payloads and other devices often use much less. It would have almost tripled total power consumption.

I looked into the EEE (energy efficient ethernet) standard and it didn't seem workable for using COTS things, it only seemed workable if you had design authority over everything.

I kind of knew changing the physical layer was possible but I didn't know where to start, and anyway the microcontrollers I had picked out at the time because they "had ethernet" turned out to be very hard to use with more standard devices, defeating the point.

Another couple of questions. I like gecko connectors but why not choose the ones with mating screws? Also interested in criteria for selecting the Tyco connectors.

By the way, there is a small company that makes very tiny ethernet switches[1] for drones. There are 100Mbps and 1Gbps versions and they have nice connectors you are probably already familiar with. They are very nice for development of embedded stuff, even if you don't integrate it in your project and just use it for the sake of getting a pile of routers off of your desk.

[1] https://gadgetsmyth.com/shop/

Note: My opinions are my own and not those of my employer.

crote• 2 years ago

Huh, what a neat project!

Especially the Ethernet-over-UART/SPI/whatever part is quite interesting. It's incredibly obvious in hindsight, but it's of course a great way to create affordable wired IoT devices. You could just talk Ethernet over RS485, and be able to communicate to a bunch of devices with a single $20 translator and a $0.15 transceiver per device!

ooterness8• 2 years ago

Yes, that's a great example of the "mixed-media" use case for SatCat5. If you have an Ethernet switch where some ports are Ethernet-over-RS485, and others are Ethernet-over-10/100/1000BASE-T, then the switch doubles as a sort of media converter. Using a common transport layer means it's easier to link sensors, actuators, and compute resources.

wrs3• 2 years ago

Maybe I’m just looking in the wrong places, but open hardware at this quality level seems to be extremely rare. Does anyone have other good examples of complete, professional-quality open source HDL projects that aren’t CPUs? I’m thinking of the hardware equivalent of PostgreSQL, something truly industrial strength with readable code you can learn from.

ooterness8• 2 years ago

The open-source community for gateware is not as large or well-developed as the one for software, but there's many good projects out there.

OpenCores [1] has been around a long time, and there's many high-quality FPGA IP-cores hosted there. The Open Hardware Repository [2] is another good resource. Not all OHWR projects involve FPGAs, but many have full hardware/gateware/software stacks, including the White Rabbit Project [3].

[1] https://opencores.org/ [2] https://ohwr.org/explore/projects/starred [3] https://white-rabbit.web.cern.ch/

wrs3• 2 years ago

I know about OpenCores, but it consists of, well, cores. I’m looking for fully realized projects, with controller, glue logic, external interfaces, test benches, multiple hardware realizations, all the tedious stuff you have to do to make a working version>1 device. That is, what do you do with the cores? To me it seems analogous to the difference between a B-tree library and PostgreSQL. White Rabbit looks great, thanks for the pointer!

shmerl2• 2 years ago

Oh, is there an open source switch that supports 10 Gbps SFP+?

morphle2• 2 years ago

I make my own open source FPGA switches, 6 and 12 port 10 Gbps SFP+ up to 100 Gbps QSFP28. Older model described in [1]. Email me if you want one.

I also sell cheap $150 10 Gbps and 25 Gbps QSFP28 switches but they are only partially open source.

They still sell some of the NetFPGA models, very pricy [2].

There are a few Chinese and Russian switches but you can't buy them anymore because of the war.

[1] https://www.researchgate.net/profile/Merik-Voswinkel/publica...

[2] https://netfpga.org

shmerl2• 2 years ago

I make my own open source FPGA switches, 6 and 12 port 10 Gbps SFP+ up to 100 Gbps QSFP28.

How big is it physically? I don't really get it from the link.

ooterness8• 2 years ago

Development of SFP+/XAUI is on our wishlist for SatCat5, but not yet supported.

gigatexal• 2 years ago

In my next life I will go to college an study computer engineering. It never ceases to amaze me the cool stuff you hardware hackers can do.

zokier• 2 years ago

One of my dream projects would be to grab some off-the-shelf switch IC and build OSHW switch around it with fully free blobless Linux based software stack. Something like SparX-5 [1] could work here, and the vendor software is already Linux based (but presumably absolutely horrible). The problem is that you'd need fair chunk of cash to get anywhere, so this basically needs a kickstarter or something to get going.

[1] https://www.microchip.com/en-us/product/vsc7552

tonyarkles• 2 years ago

You might be interested in some of the stuff Andrew Zonenberg is working on: https://ioc.exchange/@Azonenberg. I don’t have a link to a specific post, he usually has a couple of things on the go and they all get interleaved. Pretty wild Ethernet stuff in there!

RantyDave4• 2 years ago

How do you packetise stream formats (ie UART)?

ooterness8• 2 years ago

SatCat5 uses the Serial Line Internet Protocol (SLIP) [1] to provide frame delimiters. Each SLIP-delimited frame contains the normal Ethernet MAC-layer header and footer (i.e., destination MAC address, source MAC address, EtherType, user data, CRC32 frame check sequence).

[1] https://en.wikipedia.org/wiki/Serial_Line_Internet_Protocol

RantyDave4• 2 years ago

SLIP lives!

RantyDave4• 2 years ago

Why Ethernet and not SpaceWire? Surely you don't need multiple hundreds of mbit/sec across a cubesat?

ooterness8• 2 years ago

We continue to use SpaceWire where it's appropriate, and it was one of many options considered in the initial trade-study [1] that led to the creation of SatCat5. Among other things, many Aerospace-built cubesats have a laser communication downlink [2][3] that can reach 250 Mbps and up. It's not hard for raw sensor or video data to saturate a 1 Gbps link, and future missions may even need 10 GbE.

[1] https://digitalcommons.usu.edu/smallsat/2020/all2020/174/ [2] https://www.eoportal.org/satellite-missions/aerocube-ocsd [3] https://aerospace.org/article/aerospaces-slingshot-1-demonst...

RantyDave4• 2 years ago

I had no idea that laser downlinks were even remotely possible from a cubesat - that's really kinda astonishing. Regarding the other high bandwidth stuff I imagined that "a communication satellite" was more or less a life support machine for a box made by Nokia.

CAN is actually kinda cool, should you ever feel like going down a rabbit hole.

retrochameleon• 2 years ago

Interesting. Seems like it could be useful for custom ethernet protocols, eg. USB or HDMI over ethernet

Show HN: SatCat5, the open-source FPGA Ethernet switch

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