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USB using nonstandard connectors
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rakeshm55:
I want to have a non standard connector on chassis to handle USB. From my board USB signals will be routed to front panel PCB with chassis circular data  connector.
How to do the wiring for it??
I am looking for a High Speed USB2.0  standard.

I guess I need to consider following signals
VBUS
GND
D+
D-

What to do with the braid shield of usb cable.?? Should I route it to main PCB

What for a HS USB 2.0 480mbps what kind connectors i need to consider to avoid impedance  mismatch.
Gyro:
If you look closely at a standard USB connector you will see that the VBUS and GND contacts are longer - they are designed to make contact before the D+ and D-. This is for ESD and proper signalling purposes. Whatever connector you use would have to mimic this action.

Normally you would want a pretty good reason for deviating from standard USB connectors.
T3sl4co1l:
Noteworthy experience:

Had a customer who wanted to use USB to communicate to peripherals (using a noncompliant supply voltage), in an automotive environment.

They insisted on plastic circular connectors and unshielded cables (actually the cables were shielded, but that means nothing if it's not maintained throughout the connector and harness).  Mostly for cost.

We pushed back, suggesting they use a more traditional RS-485 interface, or the like.  They insisted.

Come testing day, and their peripherals are dropping like flies when hit with radiated and fast-transient (EFT) interference.

Possibly, they could've at least addressed it in software (they were running a Linux SoM), but it seems their devs never got around to it, or perhaps weren't experienced enough with Linux, or were in general too heavily loaded with other activities to address it.

We had to put the guts inside shielded enclosures, with metallic connectors tied to the cable shields.  That got it to pass several kV of EFT, more than good enough.  (It didn't need to be quite as robust as it ended up, but there was no just-good-enough option available that was cheaper.)

The customer needed a $50 module, which would've been fine otherwise.  But we ended up delivering a $200 module.

That IP66 rated EMC box sure is sexy.  It doesn't even make sense when you look at it -- the gasket feels sandy, how can it seal?  But lo and behold, it does indeed seal against dust and water, and it does indeed conduct very nicely (a couple of ohms between any pairs of points inside the enclosure).  But that price...

Tim
Gribo:
There are chassis mounted round USB shells, from the usual suspects (TE, Amphenol, Samtec and others). If you also require miniature size, you are practically on your own.

Example:https://www.alibaba.com/product-detail/Cnlinko-IP67-usb-type-a-usb_60290321922.html] [url]https://www.alibaba.com/product-detail/Cnlinko-IP67-usb-type-a-usb_60290321922.html
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T3sl4co1l:

--- Quote from: Gyro on November 09, 2018, 01:26:07 pm ---If you look closely at a standard USB connector you will see that the VBUS and GND contacts are longer - they are designed to make contact before the D+ and D-. This is for ESD and proper signalling purposes. Whatever connector you use would have to mimic this action.

Normally you would want a pretty good reason for deviating from standard USB connectors.

--- End quote ---

This.  They make IP-rated USB connectors -- pricey, basically a rubber boot molded over two ends.  Awkward as hell.  But you don't have to do any of the hard work we did and bang your head against impossible requirements.  It just works.

To actually answer the question: the shield goes to PCB ground, and GND is always* shield, so that's fine (or you can make it a pass-through, it's just a connector board, right?).  The ESD note is a good one, and adding ESD diodes on the connector board might be worthwhile (else, at the USB interface chips).  USB High Speed should be alright in a reasonable quality shielded twisted-pair cable.  Don't worry about mismatch in the connectors, they aren't long enough to matter.  You still have to obey maximum cable length restrictions.

*I haven't seen any exception to this.  I haven't read the USB standard in enough detail to know if they made note of any cases where you might want isolation between them.

Tim
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