Technology: The (nearly) perfect USB cable tester does exist

4 days ago (blog.literarily-starved.com)

The thing that has been bothering me for a while is that the USB spec allows for software detection of capabilities. You can read the emarker data and see the supported protocols, speeds, voltages, etc.

But there is not standard for usb controllers to present this data to the OS. So it’s stuck in the low level firmware and never passed up. In theory we could have a popup box that tells you that both your computer and other device support higher speeds/more power, but your cable is limiting it.

Apple seems best able to do this since they control the hardware and OS, yet they aren’t doing it either. Users are just left to be confused about why things are slow.

  • > But there is not standard for usb controllers to present this data to the OS. So it’s stuck in the low level firmware and never passed up. In theory we could have a popup box that tells you that both your computer and other device support higher speeds/more power, but your cable is limiting it.

    There is. I used to use a KVM with USB 2 ports connected to my PC's USB 3 port, to which I connected a monitor with integrated USB 3 hub to drive my keyboard and mouse. Windows would show a popup every time telling me that I should use a faster cable.

    There are also popups telling me that my laptop is connected to a "slow" usb-c charger.

  • > In theory we could have a popup box that tells you that both your computer and other device support higher speeds/more power, but your cable is limiting it.

    I'm pretty sure my old Dell XPS laptop with Windows 10 had pop-ups just like this.

    "This device can run faster" or something.

    • I wonder if it's possible for a regular machine with two high speed ports to do a cable test by itself. Maybe it can't test all the attributes but could it at least verify speed claims in software?

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  • On iPhone, when connecting an external MIDI device via USB, the phone told me that the device was drawing too much power and would be disabled.

    I don’t know if they check that via USB protocol, or if they are measuring the actual power draw on the USB port.

    In order to use the device, I had to connect it via an externally powered USB hub.

  • I suspect most users do not even realise things are slow.

    • Oh, they very much do. But like with everything in technology, they can do fuck all about it, so they resign and maybe complain to you occasionally if you're the designated (in)voluntary tech support person for your family and friends.

      Regular people hate technology, both for how magical and how badly broken it is, but they've long learned they're powerless to change it - nobody listens to their complaints, and the whole market is supply-driven, i.e. you get to choose from what vendors graciously put on the market, not from what the space of possible devices.

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I wasn't surprised to learn that when Linus Tech Tips released those new usb-c cables, that they all sold out almost instantly. They put their entire reputation on the line to claim (and label) the exact capabilities of their usb cables. Isn't that all we really want?

I want one that sends a pseudorandom data stream and tells me the bit error rate.

  • Yup, that's the sort of thing that's typically missing from cable testers. I have a USB cable that normally works fine, but introduces errors when doing full blast USB 2.0 bulk transfers. I keep it around just in case I ever come across a tester that can show me this in hard numbers.

This isn't a Beagle. When I first read the headline, I was hoping that it would be more than a smart continuity tester.

It seems to be a more comprehensive "Make sure the lines go where they are supposed to" tester. Looks pretty good.

But the devices that test things like transmission speed, are a lot more expensive.

I think that many of the issues that this device tests, can be mitigated by simply buying cables from reputable sources.

As someone who really doesn't care about learning the details, and just want one USB-C cable that does it ALL to put in my backpack what should I buy ?

  • You don’t really want that. A thunderbolt cable is both stiff and expensive. They only really make sense to leave attached to the back of a monitor or dock.

    What would work better is a flexible 100w+ usb3 cable. You can’t do thunderbolt on it but it’s a tiny fraction of the cost and does everything you’d actually need on the go.

    If you actually do want it, this is the do everything cable https://www.apple.com/au/xc/product/MW5H3ZA/A

    • At my workplace someone always orders the what they perceive to be the "best" cables. They aren't thunderbolt, they are just oversized with thick braiding. They are all so stiff and heavy you can barely handle a phone while charging without the cable pulling itself out.

One thing to realize is that especially for high resolution video cables these cheap testers can't really deliver. The way to test them is a eye diagram (see: https://incompliancemag.com/eye-diagram-part2/ ) and testers with that capsbility cost upwards of 10.000 Eurodollars.

  • So you're saying there is something to audiophile grade HDMI cables?

    • No. What it can affect though is the bandwidth of the cable, meaning e.g. for HDMI cables, they might not support higher resolutions or framerates. If it's on the border you might see random disconnects or screen blanks.

      The quality degrading is not something you will see, as it's a digital protocol.

      "Audiophile grade" HDMI cables are likely to just be a Shenzhen bargain-bin special with some fancy looking sheathing and connectors. I would trust them less than an Amazon Basics cable.

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    • No. What I am saying is that it is hard to test the quality of a 8K 240Hz 4444 video cable without having a device that can send and receive this or even higher.

      If you send bits across a line fast enough you're grtting into the territory of RF electronics, with wrong connector or conductor geometry you will get echos on the line and all kind of signal loss. A good digital protocol should keep this at bay with error correction and similar mechanisms, but if you want to know what the good cable is on a better than binary scale of works/does not, you need to look at these things.

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I just want one that tells me the maximum voltage and current supported by a USB C cable.

I’ve had one for a while as well. I don’t use it often, but frankly I couldn’t sort my cables without it.