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Author Topic: Intel Paper about USB shelding  (Read 3085 times)

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Geek-9pm

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Intel Paper about USB shelding
« on: August 04, 2017, 02:45:17 PM »
Here it is...
Back in 2012 Intel did a White Paper with this title.
USB 3.0* Radio Frequency Interference on 2.4 GHz Devices
Sub title:
Document:  327216-001
USB  3.0*  Radio Frequency Interference Impact on 2.4  GHz  Wireless Devices
https://www.intel.com/content/www/us/en/io/universal-serial-bus/usb3-frequency-interference-paper.html

I learned about this from another source and had never read the full report from Intel. The paper provides some details that I thought were unusual.

I might mention that a level of -90 db would not be a problem for most PC users. The paper shows some effort can reduce the radiation down to  almost  -100db. See the paper for derails. Here is a screen shot from the PDF.


Image above is chart from Intel.
« Last Edit: August 04, 2017, 03:16:31 PM by Geek-9pm »

BC_Programmer


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Re: Intel Paper about USB shelding
« Reply #1 on: August 04, 2017, 04:17:38 PM »
Quote
I learned about this from another source and had never read the full report from Intel.
I linked it, so that must be me. And while I certainly cannot claim to have read the report, I did read the title, which makes it clear that it is about USB3 interfering with other devices, not the other way around.
I was trying to dereference Null Pointers before it was cool.

Geek-9pm

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Re: Intel Paper about USB shelding
« Reply #2 on: August 04, 2017, 04:26:12 PM »
I linked it, so that must be me. And while I certainly cannot claim to have read the report, I did read the title, which makes it clear that it is about USB3 interfering with other devices, not the other way around.
It has been reported. It is in the Linux stuff.
Code: [Select]
In stable: 2.4.37.10 2010-09-06
in /drivers/usb/hub.c

    /*
    * EM interference sometimes causes bad shielded USB devices to
    * be shutdown by the hub, this hack enables them again.
    * Works at least with mouse driver.
    */
    if (!(portstatus & USB_PORT_STAT_ENABLE) &&
    (portstatus & USB_PORT_STAT_CONNECTION) && (dev->children[i])) {
    err("already running port %i disabled by hub (EMI?), re-enabling...", i + 1);
    usb_hub_port_connect_change(hub, i, portstatus, portchange);
    }
from http://www.linuxquestions.org/questions/linux-newbie-8/usb-port-nn-disabled-by-hub-emi-re-enabling-841593/
Another:
https://electronics.stackexchange.com/questions/31417/how-can-i-improve-usb-emi-insensitivity
Quote
I have several devices and some long cables on my PC's USB buses and every now and then I get a message like hub 6-0:1.0: port 2 disabled by hub (EMI?), re-enabling... on my Linux machine. Especially the devices on my desk (keyboard, mouse, 2 Arduino's) are being disconnected and reconnected. These devices respond to electric shutters for the windows, but also from passing motorbikes.

What can I do to improve immunity to EMI?

Tried ferrite cores on the mains cable of the shutters and some other equipment, but doesn't really improve much.
This is found only on Linux.   
« Last Edit: August 04, 2017, 04:42:41 PM by Geek-9pm »

BC_Programmer


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Re: Intel Paper about USB shelding
« Reply #3 on: August 04, 2017, 04:48:56 PM »
When a connected port is changed to disabled by the hardware, that implemented logic enables it. The interference consideration is an assumption made in the code as to a possible cause, but it's not really documented/reported as being the actual cause- it's just an assumption about one possible cause for the oddity that it addresses; It's really just handling USB2.0's Port_Error which can be caused by any number of things.

Remember that your original claim was that Interference caused by leaving a PC case open would cause USB devices to run slower and drop to reduced standards. Nothing you have provided (yet) substantiates this.
I was trying to dereference Null Pointers before it was cool.

Geek-9pm

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Re: Intel Paper about USB shelding
« Reply #4 on: August 04, 2017, 06:09:58 PM »
The purpose of this post was only to share the Intel Paper.
The Intel paper is only about an External HDD using USB 3.0 and a wireless mouse.  I was surprised that it could interfere with a wireless mouse at close range. One would expect a wireless mouse to have signal at about -50 db and in the report they never said what level the mouse had. They only said the external HDD was found to be at about 88 db. I would think that if the information was wrong, Intel would have retreated the paper by now. Now a SNR of 30 db is more that enough, I think.
I do not have any way to measure signal levels here. Other that what I get from a client Wi-Fi device, which is not very accurate. I recall I can get usable Internet with a SNR of only 15 db. Hard to figure.

Now if and wWhen I find more information about the other topic, I will report it in a new post.

The Intel Paper provides some information on how measurements are made in questions about unwanted and harmful radio signals. That is with regard to operation of electronic equipment. Not about alleged harmful effects to birds, Goats, people and other things.  :)

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Re: Intel Paper about USB shelding
« Reply #5 on: August 04, 2017, 07:08:37 PM »
It's still balderdash Geek...

Your citations are unfounded...and it seems you have grouped RFI and EFI into 1 symptom...
" Anyone who goes to a psychiatrist should have his head examined. "

BC_Programmer


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Re: Intel Paper about USB shelding
« Reply #6 on: August 04, 2017, 09:26:25 PM »
The purpose of this post was only to share the Intel Paper.

I see now I misread part of your original post- I had read

Quote
I learned about this from another source and had never read the full report from Intel.
as

Quote
I learned about this from another source who had never read the full report from Intel.

which felt a bit inflammatory.

Just to be clear on the whole thing- I'm sure at high enough levels, Radio interference could interfere with the operation of the USB protocol. I'm not saying it is wholly impossible (though I may have accidentally implied that, in which case I concede the point) Just in the case where this originally cropped up regarding side panel removal, I just don't see how removing the side of a case could increase any interference to that level.

Of course, it can definitely cause problems for analog data, such as audio devices- I've had cases where I can "hear" a wireless card working, for example, and my old PowerMac G4 clearly emits very quiet tones that seem related to the CPU usage.

And wireless data is in many ways analog; or at least more susceptible to radio interference because it is literally working via a radio. it's just that for USB I'd expect that interference from consumer sources to have little effect due to how USB works via a digital differential signalling protocol. I can see RF interfering directly with end devices, of course, which could travel through the cord and affect other aspects of the system (again, analog signalling stuff for example- or as mentioned, wireless)


Or- perhaps I misunderstood what was being said in that case? A USB3 root hub in a PC could interfere more readily with analog sources outside the PC with the side panel off, for example. I was interpreting it the other way around.


On the topic of the wireless interference consideration, I actually dealt with this myself. Or rather, didn't deal with it but worked around it. I found that if I had a USB3 device plugged into my computer, my wireless game controller needed me to hold it less than a foot away from the receiver dongle. But if the USB drive wasn't plugged in or it was an older USB2 drive, it worked as normal.
I was trying to dereference Null Pointers before it was cool.

Geek-9pm

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Re: Intel Paper about USB shelding
« Reply #7 on: August 08, 2017, 08:32:43 PM »
...

On the topic of the wireless interference consideration, I actually dealt with this myself. Or rather, didn't deal with it but worked around it. I found that if I had a USB3 device plugged into my computer, my wireless game controller needed me to hold it less than a foot away from the receiver dongle. But if the USB drive wasn't plugged in or it was an older USB2 drive, it worked as normal.
So you confirm he results of the Intel Lab tests. In the tests they concluded taht the main cause of the interference was not the cable, but the device at the end of the cable. In the Intel test it was a HDD that was not shielded. Adding a shilled in the form of aluminum foil reduces the interference.
With USB 2.0 a lower data rates will be selected. This means fewer transitions in a time period, which reduces the amount of energy involved.