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I need to replace the USB-B port on a device since the port is failing on me, and I'm curious how stupid it would be to attempt to make some sort of daughterboard that sits on top of the USB-B footprint on the existing board (I have no schematic) with a USB-C port. I am fully aware this may not be possible, but I couldn't find any resources on the subject so I figured why not ask?

To clarify, this is a USB 2.0 device, and I am familiar with the implications for such a task with mini or micro-B, but due to the size and unusual footprint of the full-size B connector I'm just trying to figure out if this is practical and if so how to do it.

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  • \$\begingroup\$ what is your specific question? ... what is the exact problem that you are trying to solve? \$\endgroup\$
    – jsotola
    Nov 16, 2021 at 1:38
  • \$\begingroup\$ USB B and USB C are not just same-pins-different-connector-shape. USB C is fantastically more complex than USB B. Proper USB C cables even have a microchip in them to aid in the handshaking and voltage selection. Possible to do what you ask? Technically yes. Practical? No. \$\endgroup\$
    – Kyle B
    Nov 16, 2021 at 2:22
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    \$\begingroup\$ Despite Kyle's pessimism (confusing USB-C with USB 3.x is a common mistake), what you propose is not that outlandish. USB-C is just a connector and you're not forced to use the USB 3.x SuperSpeed data lines or other features just because you use a USB-C connector. Hooking up the Vbus, GND, D+ & D- pins from your old USB-B to the appropriate pins on the USB-C will work just fine. You should be able to find a ready-made daughter-board with USB-C connector populated already to use. \$\endgroup\$
    – brhans
    Nov 16, 2021 at 3:01
  • \$\begingroup\$ If it is a USB2 device, the conversion is relatively easy. If it is a USB3 device, then a fully-compliant Type-C port will need a 1:2 MUX to steer the super-speed lanes, and a CC-controller for detection of cable plug orientation, to control the MUX. \$\endgroup\$ Nov 16, 2021 at 4:42
  • \$\begingroup\$ @brhans Hooking up similarly named wires is not all that there is. The device role needs to be set with resistor values suitablr for the role. Sure, some ready made boards might contain such resistors so the device looks like standard USB device to the host, but a board with no resistors will not directly work. \$\endgroup\$
    – Justme
    Nov 16, 2021 at 5:52

1 Answer 1

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Feature wise, Type-C is a superset of Type-B here, so this is definitely doable.

USB2 case can be implemented with only one PCB, one Type-C receptacle and two resistors. USB3 case is trickier.

Two possibilities:

  • This is an USB3 Type-B: The adapter mezzanine board should wire respective VBUS and GND all together (both orientations, both connectors) have one distinct 5.1kohm to ground on each of the CCx pin of Type-C. Then you need to do proper swapping of SS lines depending on orientation. For this, you have to take one of the CC lines (directly) and use it for controlling a SS diff pair mux (See figure 4-3 of Type-C spec). USB2 D-/D+ lines may be swapped with the switch (some have provision for this) or may be directly tied together (D- from both orientations together, same for D+) close to receptacle (USB2 spec stub allowances tolerate this, see Type-C spec, Table 3-4, note 1).

  • This is an USB2 only Type-B. For power, and CC, and USB2 do the same as above. Other lines (SSx, SBU) can be left floating. With tie-together option above, this is a passive-only solution.

In either case, you do not need a Type-C CC Port controller IC because you do not need Power-Delivery. Plug orientation will be reflected on receptacle CC lines passively (one will be tied to ground by cable, other will be pulled by remote DFP through cable. See figure 4-5). In the worst case, you’ll need a comparator to adapt to Threshold voltage of switch control pin. (Note some switches have built in CC handling)

In both cases, relevant impedance matching of data pairs should be taken care of.

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