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Thread: USB Host - shielding - connect to GND or not?

  1. #1
    Senior Member+ Frank B's Avatar
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    USB Host - shielding - connect to GND or not?

    Thinking of ground loops, EMI, etc:
    A question re: USB Host
    Should I connect the shielding of the USB Connector for the HOST to GND or is it better to do this not?
    Is there a difference with Teensy 4 and Teensy 3?

    For the client-side: Is the shielding always connected to GND?
    Last edited by Frank B; 02-26-2021 at 04:43 PM. Reason: shield->shielding

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    Senior Member+ mjs513's Avatar
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    @Frank B
    Assume you are talking about the USBHost Shield 2.0: http://shop.tkjelectronics.dk/produc...products_id=43

    If you are I have the original version and it works for teensy 3 and 4 with one caveat. SPI connections go through the 6 pin connector so you have to jumper them to correct Teensy pins. They don't go to the shield pins.

    As for attaching never had to do anything special. Just plug the cable in and go.

    If you are talking about a knock off = the only one that I know that works reliably is the sparkfun version.

  3. #3
    Senior Member+ Frank B's Avatar
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    Sorry, I'm talking about the schielding of the cable.
    The usb cable has GND wire, and a shielding that must somehow be connected to GND, too.

    My Question is: Is the cable shield connected on both ends to GND? If, not on which side? Or, are there aditional parts needed (capacitors, a ferrite..?)

    In the past, with Teensy 3.6, for the USB-Host pins, I just connected GND and shielding together. That worked.. but is it the same with the way faster 480MBit USB?

  4. #4
    Senior Member+ Frank B's Avatar
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    Ok, on the Teensy 4, the 2 pins are just connected to GND.. I assume one is the GND wire in the cable, the other for the shielding?
    So, that seems to be OK.

  5. #5
    Senior Member+ Frank B's Avatar
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    Oh.. just noticed.. that the 4.1 has the TPD3S014 on board .. t4.0 not.
    Seeing this the first time.. great.

  6. #6
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    The recommendation from TI seems to be direct grounding at host end, ferrite beads to groundplane at client end. https://www.ti.com/sc/docs/apps/msp/...sb/emitest.pdf

  7. #7
    Senior Member+ Frank B's Avatar
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    Found some great PDFs in German, from Würth Elektronik.
    They say VBus (5V) should have a ferrite.
    More advanced designs they propose have pretty complex schematics, just for the connector - with a lot of parts (diodes, chokes, caps.) - don't think thats needed for my application.. but makes much sense if you want to connect a audio device!

  8. #8
    Senior Member+ Frank B's Avatar
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    They even have connectors with inbuilt electronic ... filtering and EMI protection...
    amazing!
    Click image for larger version. 

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    WE-EPLE USB 2.0 Jack with Integrated EMC Filter combines for the first time an EMI filter, ESD filter, and connector all in one USB component. This device is fully compatible with a standard THT USB 2.0 jack. Simply replace an existing plug with this USB 2.0 EPLE jack. Würth Elektronik WE-EPLE provides ESD Protection of data channels and VDD. It features ultra low capacitance of 2pF typical. The integrated EMC filter eliminates broadband interference on voltage and signal lines, and at the same time, is almost invisible for the signal lines. This device features VCC filter impedance above 100Ω in the 20MHz range to an excess of 1GHz. It offers common-mode suppression at 240MHz in excess of 250Ω. WE-EPLE features ESD suppression at levels of 10V at level 4 ESD pulses with 15kV.
    It's a bit expensive.. I think If I can find it somewhere, I'll order one and build an adaptercable.
    Last edited by Frank B; 02-26-2021 at 06:16 PM.

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