Dual USB-C Expansion Card

@Daniel_Gilbert a lot of designs would want to use a PD controller. however since you are just doing usb 3.2 you could get away with something a bit simpler if you do not implement VCONN or PD (which should not be necessary for just usb3.2 + 5V output).
You can add the appropriate Rp pullup to each CC pin, and detect when it drops below the threshold voltage to determine the cable orientation by sensing Rd.
You might do this with a small mcu with 4 adc channels.
I agree using an all integrated type-c hub would be an easier solution :slight_smile:

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Laypersons question; It appears from the CAD modeling like there is enough space fit 2 PCB’s in the module. One board to control each individual USB-C port. What engineering restrictions prevent that?

Not an engineer by any means but… would it be possible if, on the dual USB-C module, just don’t allow charging… It would still increase the amount of USB-C ports and you simply put a single USB-C in one of the other 3 spots.

Saying that, I do think it would be nicer for it to just be a dual USB-C with charging allowed.

Cudo’s to the FW team…

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@Reese_Borel it is very much possible to do without PD. It’s just something that would be nice to have.

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gen 3x2 (actually USB4 gen 3x2) means 2 lanes of 20 Gbps for 40 Gbps total. This is used for USB4 and not USB 3.x.

I think you meant USB 3.2 gen 2x2 (2 lanes of 10 Gbps USB for 20 Gbps total). USB 3.2 gen 2x2 is optional for USB4. Intel’s Thunderbolt 4/USB4 (integrated TB of Tiger Lake or discrete TB of Maple Ridge) does USB 3.2 gen 2x1 (10 Gbps USB) but not USB 3.2 gen 2x2 (20 Gbps USB).

There are USB4 gen 2x1 and gen 2x2 modes but that’s for USB4 data (like the gen 3 modes).
USB4 - Wikipedia

Thunderbolt is not the same as USB4 (not until Thunderbolt 4):

  • Thunderbolt 1 uses two separate lines/channels of 10.3125 Gbps (separate links).
  • Thunderbolt 2 supports that plus a two lane mode (channel aggregation for 20.625 Gbps total).
  • Thunderbolt 3 adds a 20.625 Gbps link rate to that (41.25 Gbps for a single link that uses channel aggregation).
  • Thunderbolt 4 adds USB4 modes.

Anyway, even if USB 3.2 gen 2x2 was supported, I don’t think there’s a USB 3.2 gen 2x2 controller that can split that into two different gen 2x1 ports? I haven’t even heard of USB 3.2 gen 2x2 hubs yet.

Now, if you want the two USB ports to do 10 Gbps simultaneously, then I think you need to use a Titan Ridge Thunderbolt 3 controller (JHL7440). Use one Thunderbolt port for upstream, one Thunderbolt port for downstream, one USB port for other downstream. It could support DisplayPort Alt Mode too by also using the DisplayPort output of the Titan Ridge (but you need a USB-C controller to combine the USB and DisplayPort).
https://thunderbolttechnology.net/sites/default/files/18-241_Thunder7000Controller_Brief_FIN_HI.pdf

You probably don’t want to use Goshen Ridge Thunderbolt 4 controller, because it might default to USB4 tunnelling which uses the USB controller of the USB4 host instead of the USB controller of the Goshen Ridge, and that would make the downstream Thunderbolt 4 ports share the same USB 10 Gbps. But maybe Goshen Ridge makes DisplayPort Alt Mode easier and it would give at least two downstream Thunderbolt 4 ports so while they aren’t good for dual USB (only 10 Gbps total instead of 20 Gbps), they would be good for one Thunderbolt + one USB, or two Thunderbolt (≈23 Gbps total).

The problem is (excepting high cost of Thunderbolt docks), there’s probably not enough room for all the chips/components required for a Thunderbolt dock in the Framework expansion card form factor. A dual PCB sandwich would give 4 surfaces for components? There’s only 6.8mm height though, not including the thickness of the top or bottom enclosure surfaces. I suppose you could do without those and just use the PCBs for the surfaces and just insulate with tape. There’s also an extra 2.0 - 3.0 mm of height that could be used due to the rear foot of the laptop.

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That purgo is connected to two Thunderbolt 3 ports of the MacBook Pro so it’s not applicable here, unless you want to make a similar external dock for the Framework Laptop that connects to two expansion card slots. Making it external like that eliminates restrictions caused by the Framework expansion card form factor but it also eliminates the benefits (being flush with the Laptop’s exterior sides).

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I would also vote for a full feature usb c + usb a, or if that’s not possible, drop the thunderbolt functionality, as long as usb c PD is preserved.

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I just received my frame.work today and as I was putting together thought to myself that 2 USB C seems easy enough to fit on one expansion card. Came here to make the suggestion and found this thread! I currently have my frame.work equipped with 2 x USB C and 2 X USB A. I bought an HDMI expansion card but since I won’t be using it as often, I don’t keep it plugged in.

I am very interested in a 2-USB C expansion card that would only be used for charging or low-power USB2/3 accessories! It kind of makes you wonder what other cards could be combined. Micro SD + USB C on the same card?

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It’s a shame that preserving Alt Mode would be a challenge because a dual port card with the right spacing could enable compatibility with MacBook accessories opening a huge range of drop in scenarios for the Framework to replace MacBooks.

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@Daniel_Gilbert Just dropping in to say thanks for all the work so far on this. I would love to see a 2-port USB-C, with or without the advanced features. So cool that there is such great community involvement on things like this (and Framework support for it too)!

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I’m hoping I don’t have to hack this up myself, please make a dual USB module. :slight_smile: Even if it has to be USB 2.0. I always use at least one port for a mouse. And the other one could be used for charging devices or connecting various stuff.

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I’d 100% be on board with having a little extra USB-C available - especially for less bandwidth or power intensive activities.

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I would love to see more that 4 ports on the framework laptop, and sacrificing one for power only, or less functionality would be very reasonable for my uses. I’m seriously considering only ordering 1 regular usb-c expansion card instead of 3 and adding your dual usb-c card and some other ports when yours is available.

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I love the concept, hope it comes together and works.

If I were in charge of designing this, I would flip the PCB over so that the two external C ports were a little higher up. I could see having them right on the very bottom being an issue for thicker cables.

No thermal issues with your chosen PCB enclosed in this expansion card case I assume?

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Can one port be just for charging and the other as ‘normal’ USB-C? Since the laptop will always use one port for charging anyway, why not just ‘dedicate’ one USB-C for that. If it doesn’t have to handle data signals etc, could be doable?

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Let me throw another +1 your way, I would definitely be interested even without TB and PD a two port card would be just fine for low bandwidth accessories.

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An idea I had was to to a multifunction port that clicked into one socket, but was double-height, and was expanded to cover up the other socket on the bottom. You’d have to buy these in pairs, of course, but you’d get whatever ports the silicon could fit (say, a pair of USB-C’s at the MacPro spacing on the bottom half, plus a Micro-SD slot or USB-A slot in the normal position.

If no one else is working on this (speak now or forever hold your peace :slight_smile:) I’d be willing to give this a shot.
No PD- designing a charge through hub (which is what this would be) is really effing complicated, and it’d be faster to plug straight into the laptop to charge anyway since there would be derating. No thunderbolt because that’s also effing complicated and I’m not friends with Intel ;). However- USB 3 would totally be on the cards- no need for USB 3 muxes (like, in a silicon shortage? no!)- you can just use a 4 port hub and wire up 2 electrical USB ports to one physical one, like they do on some PC motherboards and PCIe cards.
Anyone interested? Thoughts on USB 3 vs 2?

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I will be doing a dual USB-C as just data, no power in or thunderbolt, just standard USB-C spec as the laptop. Could be used for dongles and whatnot.

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Hi all,

Sorry I haven’t had the time and resources to devote to this particular project over the past few months!

I’m sharing the files that I do have in case anyone else wants to continue working on it or pick up from where I left off, or just reference anything that I’ve made so far.

Please note that the schematic in these files is NOT COMPLETE and should NOT be considered accurate, by any means. It is only a mockup for the beginnings of further development and testing.

Software used is SketchUp and EAGLE.

Please consider all files here to be licensed CC BY-SA 4.0. So, you may use anything here for derivative work, including commercially, but that work must be released under the same license.

All the best,
Dan

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