One amazing thing about USB-C is its high-speed capabilities. The pinout gives you four high-speed differential pairs and a few more lower-speed pairs, which let you pump giant amounts of data through a connector smaller than a cent coin. Not all devices take advantage of this capability, and they’re not required to – USB-C is designed to be accessible for every portable device under the sun. When you have a device with high-speed needs exposed through USB-C, however, it’s glorious just how much USB-C can give you, and how well it can work.
The ability to get a high-speed interface out of USB-C is called an Alternate Mode, “altmode” for short. The three altmodes you can encounter nowadays are USB3, DisplayPort and Thunderbolt, there’s a few that have faded into obscurity like HDMI and VirtualLink, and some are up and coming like USB4. Most altmodes require digital USB-C communication, using a certain kind of messages over the PD channel. That said, not all of them do – the USB3 is the simplest one. Let’s go through what makes an altmode tick.
The C In “USB-C” Stands For “Capable”
If you’ve seen the pinout, you’ve seen the high-speed pins. Today, I’d like to show you what interfaces you can get out of those pins nowadays. This is not a complete or extensive list – for instance, I won’t be talking about stuff like USB4, in part because I don’t understand it well enough nor do I have experience with it; that, and it’s certain we’ll get more USB-C-equipped high-speed devices in the future. Plus, USB-C is flexible enough that a hacker could expose Ethernet or SATA over it in a USB-C-compliant way – and if that’s what you’re looking for, perhaps this overview is what helps you figure it out.
USB3
USB3 is very, very simple – you have one TX and one RX pair, and while the transmission speeds are way higher than USB2, they’re manageable for a hacker. If you use a multi-layer PCB with impedance-control for USB3 signals and treat your diffpairs with respect, your USB3 connection will generally work.
With USB3 over USB-C, not much changes – you will have a mux for handling the rotation, but that’s about it. USB3 muxes are abundant, so you’ll hardly ever have a problem if you’re ever to add USB3-capable USB-C on your board. There’s also dual-link USB3, using two USB3 links in parallel to increase throughput, but hackers will generally neither encounter nor need this one, and this territory tends to be better covered by Thunderbolt. Want to convert a USB3 device to USB-C? All you really need is a mux. If you were thinking of putting a MicroUSB 3.0 connector on your board for a high-speed device of yours, I politely but firmly ask you to reconsider and put a USB-C socket and a VL160 on there instead.
If you’re designing a plug-equipped USB3 device, you don’t even need a mux for rotation handling – you don’t need any rotation detection, in fact. A single, non-monitored 5.1 kΩ resistor will be enough for building a USB3 flashdrive that plugs directly into a USB-C port, or making a USB-C male to USB-A 3.0 female adapter. On the socket side, you can avoid using a mux if you have a spare USB3 connection to sacrifice, though that’s not a wonderful trade to make, of course. I’m not aware of dual-link USB3 enough to say if such a connection is USB3 dual-link capable, but I see “no” as more likely of an answer than “yes”!
DisplayPort
DisplayPort (DP) is a wonderful interface for connecting high-resolution displays – it’s been overtaking HDMI in desktop space, dominating the embedded display space in its eDP form, and provides for high resolutions over a single cable, often better than HDMI can. It’s convertable to DVI or HDMI with a cheap adapter using a standard called DP++, and it’s not as royalty-encumbered as HDMI is. It makes sense that the VESA consortium has worked with USB group to implement DisplayPort support, especially given that DisplayPort transmitters in SoCs have been getting more and more popular.
If you’re using a dock with HDMI or VGA output, it’s using the DisplayPort altmode under the hood. More and more often, monitors come with DisplayPort over USB-C inputs, and thanks to a feature called MST, you can chain monitors, giving you a single-cable multi-monitor configuration – unless you’re using a Macbook, as Apple refuses to support MST in MacOS.
Also, fun fact – the DP altmode is one of the only altmodes that uses SBU pins, which are repurposed for the DisplayPort AUX pair. The overall lack of USB-C pins also meant that DP config pins had to be omitted, excluding the DP++ HDMI/DVI compatibility mode, and as a result, all the USB-C DP to HDMI adapters are actually active DP-HDMI converters in disguise – as opposed to DP++, which lets you use level shifters for HDMI support.
If you want to tinker with DisplayPort, you might need a DP-supporting mux, but most importantly, you’ll need to be able to send custom PD messages. First off, the whole “offering/requesting DP altmode” part is done through PD – resistors are not enough. Plus, there was no free pin for HPD, a crucial signal in DisplayPort, and as such, hotplug events and interrupts are sent as messages over the PD channel instead. That said, it’s not terribly hard to implement, and I’m looking at making a hacker-friendly implementation – until then, if you need DP or HDMI out of a USB-C port with DP altmode, there are some chips, like the CYPD3120, which let you write a firmware to do that.
A great thing that makes the DP altmode stand out – with four high-speed lanes on USB-C, this altmode allows combining a USB3 connection on one side of the USB-C port and a two-lane DisplayPort connection on the other. This is how all of the “USB3 ports, peripherals and a HDMI output” docks work. If the dual-lane resolution is limiting for you, you can get a four-lane adapter too – there will be no data transfer because of lack of USB3, but you will be able to get higher resolutions or framerates through two additional DisplayPort lanes.
My take – the DisplayPort altmode is straight up one of the best things about USB-C, and while the cheapest (or most mis-designed) of laptops and phones don’t support it, it’s a joy to have a device that does. Of course, sometimes a large company will straight up take the joy away, like Google did.
Google explicitly disabled it in the kernel during development. https://t.co/4QyMitc0Hq
No reason given.
Qualcomm chips since the 835 natively support DisplayPort Alt Mode.https://t.co/Bv94GsqLFL
There's not even a licensing fee involved.
— Mishaal Rahman (@MishaalRahman) October 31, 2019
On that note, let’s talk about the most complex altmode of them all.
Thunderbolt
On USB-C specifically, you can get Thunderbolt 3 – soon, Thunderbolt 4, too, but that’s fiction for now. Thunderbolt 3 is an initially proprietary specification that was eventually open-sourced by Intel. Evidently, they didn’t open-source it enough or there’s a different caveat to it, since Thunderbolt 3 devices in the wild are still being built using exclusively Intel chips, and my guess is that lack of competition is what causes pricetags firmly in triple digit territory. Why would you look for Thunderbolt devices in the first place? Aside from higher speeds, there’s a killer feature.
You can get PCIe passthrough over Thunderbolt – up to a 4x wide link, too! This has been a hot topic among people who want eGPU support or fast external storage in form of NVMe drives, and some hackers use it for PCIe-connected FPGAs. If you have two computers (say, two laptops) which support Thunderbolt, you can also link them over a Thunderbolt-capable cable – this creates a high-speed network interface between the two, with no extra components required. Oh, and of course, Thunderbolt can easily tunnel DisplayPort and USB3 within itself. The tech between Thunderbolt is extremely powerful, and tasty for power users.
That said, all this coolness comes at a cost of proprietary and complex technological stack. Thunderbolt is not something that a lone hacker can easily build upon – though, someone ought to try it one day. And, even though the Thunderbolt docks have a wonderful amount of features, the software side of things is often hit and miss, especially when it comes to things like trying to make sleep mode on your laptop work without your eGPU crashing your kernel. If that hasn’t been apparent by now, I’m anxiously waiting for Intel to get it together.
Muxes? What Muxes?
I keep saying “muxes”. What are those? In short, that’s the part that helps handle high-speed signal swapping depending on the USB-C rotation.
The high-speed lanes are the part of USB-C that’s the most impacted by port rotation. If your USB-C port uses high-speed lanes, it will need a mux (multiplexer) IC that manages two possible USB-C rotations – matching orientations of ports on both ends and the cable to the actual high-speed receivers and transmitters inside devices being connected. Sometimes these muxes are internal to a high-speed chip if it was developed with USB-C in mind, but a lot of the times they’re a separate chip. Looking to add high-speed USB-C support to a device that doesn’t yet have it? A mux will be a core element for making your high-speed communications work.
If your device has a USB-C socket with high-speed lanes, it needs a mux – captive-cable and plug-equipped devices don’t need it. As a rule, if you use a cable to connect two high-speed devices with USB-C sockets, both of them need muxes – managing cable rotation is each device’s responsiblity. On both sides, the mux (or a PD controller with a mux connected to it) will monitor the CC pin orientation and act accordingly. There are quite a few of these muxes for different purposes, too – depending on what you want out of a port.
You will see USB3-intended muxes in cheap laptops that only implement USB 3.0 on the Type-C port, and if it supports DisplayPort, you will have a mux that has extra inputs to mix those signals in. In laptops with fancier ports that implement Thunderbolt, the mux will be built into the Thunderbolt chip. For hackers developing with USB-C that can’t reach Thunderbolt or don’t need it, TI and VLI offer quite a few good muxes for all purposes. For instance, I’ve recently been playing with DisplayPort over USB-C, and VL170 (seemingly 1:1 clone of TI HD3SS460) looks like a wonderful chip for combined DisplayPort + USB3 purpose.
DisplayPort-capable USB-C muxes like HD3SS460 don’t do CC pin management and rotation detection themselves, but that is a reasonable limitation – you need to do fairly application-specific PD comms for DisplayPort, which quickly outgrows what a mux can do for you. Are you satisfied with USB3, where PD communications aren’t required? VL161 is a simple chip for USB3 muxing that has a polarity input, expecting you to do polarity detection yourself.
If you don’t want to do polarity detection either – is analog, 5V-only PD enough for your USB3 needs? Use something like the VL160 – it will do sink and source analog PD, handling power and high-speed lane rotation all in one. This is the real “I want USB3 on USB-C and I want everything managed for me” IC; for instance, the VL160 is what the recent open-source HDMI capture card uses for its USB-C port. To be fair, though, I don’t have to single out the VL160 – there’s dozens of such ICs; “USB3 mux for USB-C that does everything” is probably the most popular kind of USB-C-related IC there is.
Planned, But Abandoned
There’s a few abandoned USB-C altmodes. The first one I won’t shed a tear over – it’s the HDMI altmode; and it just puts HDMI connector pins onto USB-C connector pins. It would give you HDMI over USB-C, and it seems to have been used on smartphones for a brief period of time. However, having to compete with the easily-convertible-to-HDMI DisplayPort altmode whereas HDMI-DP conversion is typically costly, inability to be combined with USB 3.0 since HDMI requires four differential pairs, and the HDMI licensing baggage seem to have driven the HDMI altmode into the ground. It’s my sincere belief that it ought to remain there, as I don’t believe our world could be improved by adding more HDMI.
The other one is actually interesting, however – it’s called VirtualLink. A group of large tech companies have been looking into capabilities of USB-C for VR – after all, it’s wonderful when your VR headset only needs a single cable for everything. However, VR goggles need a high-resolution high-framerate dual-display-capable video interface and a high-speed data connection for auxiliary cameras and sensors, and the usual “dual-lane DisplayPort+USB3” combination couldn’t provide such capabilities at the time. What do you do, then?
It’s simple, said the VirtualLink group, you get rid of the two duplicated USB2 pairs on the USB-C connector, and use the four pins for a USB3 connection. Remember the USB2 to USB3 converter chip I mentioned in a short article half a year ago? Yeah, its original purpose was VirtualLink. This kind of arrangement, of course, requires a more expensive custom cable with two extra shielded pairs, and it also required PCs to provide up to 27W of power, hence, 9 Volt output – a rarity on USB-C ports that aren’t wall plug chargers or powerbanks. The USB2-omitting deviation from USB3 has upset some; however, for the purpose of VR, VirtualLink looked mighty useful.
Some GPUs shipped with VirtualLink support, but, ultimately, not enough – and laptops, known for their often lacking USB-C ports, didn’t bother. This caused a key player in the arrangement, Valve, to give up on adding VirtualLink integration with Valve Index, and it went downhill from there. Sadly, VirtualLink never really took off. It would have been a fun altmode to have around – the single cable thing would’ve been amazing for VR users, and the requirement for increased voltage available through USB-C would’ve also given us PD-capable higher-than-5V ports – which no laptops and hardly any PCs provide nowadays. Yes, just a reminder – if you have a USB-C port on your desktop or laptop computer, it will give you 5 V, sure, but you won’t get a higher voltage out.
Let’s look at the bright side, however. If you happen to have one of those GPUs which shipped with a USB-C port, it will have both USB3 and DisplayPort support!
Unification Brings Compatibility
The great thing about USB-C – a vendor, or a hacker could absolutely define their own altmodes if they wanted, while the adapter would be semi-proprietary, it would still remain a USB-C port at heart, working for charging and data transfer. Want an Ethernet altmode, or dual-port SATA? Do it. Gone are the days of having to source seriously obscure connectors for devices, where every docking and charging connector was different, and could cost up to $10 apiece if rare enough, if it would’ve even been possible to find it.
Not every USB-C port has to implement every single of these capabilities – many don’t. However, a lot of them do, and with each day, we get more and more out of an average USB-C port. This unification and standardization will pay off in the long run, and while deviations will occur every now and then, manufacturers will learn to get more clever about them.
OK, so I know nothing about differential signalling.
But one thing I’ve always wondered is why the plug rotation was not handled by putting the + and – lines on opposite sides. So that if the plug is connected the “wrong” way + goes to – and – to +. After decoding the signal at the receiver all you’d need to is invert the bits to get the correct data out.
No expensive muxing needed.
Obviously it’s not that easy. But why?
“why the plug rotation was not handled by putting the + and – lines on opposite sides.”
Fundamentally the problem is signal integrity and crosstalk. Just think about, say, an 8 pin connector, two rows of four, arranged 1/2/3/4 on one side and 5/6/7/8 on the other, with 1 opposite 5. Imagine you want a single +/- receive/transmit pair. You could try to put Tx+ on pin 1 and Tx- on pin 8, and Rx+ on pin 4 and Rx- on pin 5. So obviously plugging that in backwards would just swap +/-.
But electrical signals don’t actually travel along the signal pin – they travel between the signal and its return, in the electric field. And Tx-/Rx- are supposed to be the “return” of Tx+/Rx+ (or vice versa, obviously). Which means that the Tx and Rx signals will literally be crossing right over each other.
You *could* try to deal with this by making the signals complementary single-ended – basically by putting a ground plane very tightly next to each signal. But in that case you lose the common-mode noise immunity of the differential pair, which means just the simple crosstalk from Tx+/Rx- being opposite each other won’t cancel.
If you compare this to putting Tx+/Tx- on pins 1/2 and 7/8 via a mux, and Rx+/Rx- on pins 3/4 and 5/6, now the Tx/Rx signals don’t cross over at all and any crosstalk induced on the Tx or Rx pins will be somewhat common on both pairs and partially cancel.
(Obviously on a real connector there would be buckets of ground pins as well, I’m just not mentioning that for brevity.)
>Unification Brings Compatibility
Hardly, IMO USB-C brings nothing but a world on hidden incompatibility that will be hard enough to figure out for the technically minded, as the specs will not even list everything it can/can’t do, and that will only get worse as more alt modes get added and with identical looking cables being problematic too…
And most power connectors before USB-C were barrel jack, massively massively cheaper than USB-C can ever be. While most brands docking stations might have odd connectors that are a pain they also often broke out direct access to the PCI-E and other bus, often with quite a large lane count too – so faster than USB-C at least relative to their era… For the hacker that just needs USB-2, where USB-C isn’t a nightmare, just an expensive connector for the job the docking station connectors are less ideal BUT when you actually need the complex higher speed features USB-C allows its another layer of challenge to implement them.
Indeed, this is the impression I’m left with too. The standard allows for everything but nobody is going to implement everything and this is going to leave it a crapshoot whether any two USB-C devices will actually work together. I’ve already experienced this; for several years I’ve powered a tablet PC from a USB-A power adaptor with a USB-A to USB-C cable. This allowed me to carry a single adapter for my tablet and phone. Bought a new laptop and the old adapter won’t charge it — after the last article I realize it probably needs one of the higher voltages that the USB-A adapter doesn’t provide. But if you don’t know the nuts and bolts of this very overcomplicated interface, it’s not clear at all why the old cable doesn’t work.
Even a single vendor cannot get this right. We got Dell everything at the office. Dell laptops, Dell docking stations (USB3) and Dell monitors.
No matter which dock I use, I get a “display connection limited” error, a “charging limited”, only one of two screens working or just no connection at all with the dock. It’s a mess.
Dell cables too?
I had this problem at my office to.
Had to firmware update the mobo, dock, and driver update. That finally made the damn thing work. USB-C has been nothing but a headache.
student of many master of none is all I experience with USB-C
I use docking stations from manufacturers other than Dell, and it’s been a smooth journey! =D It doesn’t seem hard to build a decent USB-C dock – they generally work pretty damn well, until you get into the Thunderbolt quirk territory, and even then the problems are in ‘plug, unplug, works’ area. Not gonna lie, I’d like to see the mainboard schematic for Dell laptops with these docks, at this point.
Arya’s got it right. All my issues went away when I bought a cheap USB-C powered breakout from Amazon. Keyboard, camera, USB key, all go into that, display plugs into either a USB-C, HDMI or DP connector on the laptop and off I go. Dell docks aren’t worth the money, according to out IT guy, who told me what to do.
Nah that’s just Dell being idiots – they apparently decided to make things incompatible with USB-C while using the same connectors.
yeah if you ask me, devices like tablets need to be way more verbose on ‘why does it not charge fully’. A popup message with “Needs a USB-C charger with at least 9V@3A” would solve such problems people, and is squarely in the tablet manufacturers’ ballpark. But, welp, we can’t even trust any of them to release a single firmware update after the device hits store shelves t..t
Not only cheaper – but mainly massively more robust. How many broken USB connectors on various devices have you seen? Me a lot – and often such device ends up being discarded because it is not economical to repair it …
The USB connectors ever since micro USB are extremely flimsy and the idea of having to constantly mate and demate them, often by people who don’t align then properly, use excessive force, wiggle them side to side makes for a terrible connector. For data it is maybe tolerable but given than USB-C is now used to also power everything from smartwatches to entire laptops and all sort of electronic gizmos that don’t use data at all, the broken connectors are going to plague us more and more – and for no good reason.
Very true, I’ve only seen one broken barrel jack that was trivial to repair (if you discount the dell BS version with its only works right on the proprietary charger it can talk to, which is so delicate it breaks even if you never cycle it..). The USB-C connector is going to be a PITA even for a skilled repair person, way more footprints on the PCB, massive more tiny pins to solder…
Barrel jacks are typically rated for half (or less) the cycles than a decent USB-C connector. It’s just because the center pin flexes each time you insert it, and with USB the lever arm’s shorter. I’ve seen plenty of usage-damaged barrel jacks.
Part of the reason USB-C seems less robust are cheap connectors or cables. If you find one that looks “sleeker” or “cooler” with shaped overmolds or something, chances are it’s crap. Just by major manufacturer cables that have specs and drawings.
The other reason is you use USB-C way more than a barrel jack. Phones get plugged/unplugged each day, sometimes multiple times.
Finally, and this part I do agree with: it’s easier to damage a USB-C connector if you’re a ham-fisted human who’s not careful. And that’s probably by far the more common failure mode.
I’ve had barrel jacks on my laptop at school from way back in the time where battery life was NEVER more than a handful of hours for the best battery life machines, so the cheap one I had could maybe manage a whole lesson on battery – so it was plugged in 5x a day at least, probably rather more. And for all those years it never failed, and that is in a school environment where the power cable would get caught, bumped and yanked many times in a day as where you had to plug it in was awkward and the desk space too small its constant musical chairs…
MOST barrel jacks, especially the style that is most in use are stupidly durable and the cycle count really isn’t the issue for longevity most of the time in the real world anyway – its the ability to survive some lateral loading, to not short out on that little bit crud, to not get packed with dirt its impossible to remove that prevents the contacts from reaching type stuff. Not can it make good contact under ideal conditions for more cycles, as once you get to surviving a few thousand cycles its more than the rest of the device will last anyway….
As I’ve replied somewhere else, it took me 30 minutes to replace a fully featured 24-pin USB-C port using just a soldering iron, hot air and some flux. If I, with my getting-outdated laptop repair skills, can replace a full 24p “SMD pads under package” USB-C port, repair shops have no excuse. Remember, repair shops have been handling BGAs for a decade+ now.
Yes a repair shop can handle it, but the more complex and pin dense it is the more time and/or equipment it will take to get it right, and so the more it will cost. The 2-3 pads with really wide spacing and only 2 conductors of the barrel jack take so much less time and have so much less chance to go wrong.
Oh and of course actually sourcing the right part – that SMD USB-C is so wildly varied, always expensive as a connector goes and you really can’t take the ‘wrong’ part you can get and make it fit with such tight tiny footprint connectors…
it feels like every article in the USB-C series has a negative comment from you under it =D
pressed ‘Enter’ too fast.. of course, I meant to write more than that!
Me and my friends have been looking through the old docking station ecosystems for some time now, specifically laptops. They are a mess of proprietary and inter-incompatible connectors, often with some nasty bodges to implement the capabilities they tout (and associated limitations); the schematics for Thinkpads are quite available now, and you can spot these limitations. PCIe was cool to have on these, but it was nowhere near being abundant. With USB-C, the standard package deal for docks is “USB2, USB3 and DP”, and that’s already enough to cover, and if you want PCIe, there’s a good amount of Thunderbolt docks that expose it, i.e. through a NVMe slot, ie here’s an example of tapping PCIe from a WD D50.
Expensive? If you want USB3 from USB-C, you only need a mux. If you want DisplayPort, you need a mux and a PD controller IC. How is that expensive?
As for the first paragraph, that’s just like, your opinion. Every new piece of tech has its edges get smoothed out over time, and USB-C is no exception – you can already see that in action, if you look.
Except this one CAN’T just be smoothed out by time, it seems rather certain it is just going to get worse as the standard and its many optional extras keep evolving and nothing on the devices ports, the cables or even the spec sheets for the devices really tells you which bits it does and does not do, and unlike USB1 through USB3 where everything would just work (data wise anyway – powered hub may be required) at the slower rate there is complete incompatibility being so very possible…
For it to smooth out with time the spec has to be actually be static enough and with visible indicators of the features available and generation differences – SO M.2 for instance is a pretty deep standard with so many varieties, but the keying of the device and sockets separates the incompatible, and if it fits it will work even if its older meeting newer hardware as its all like USB1-3 able to run at slower spec speeds it doesn’t need to know the secret handshake for the newest versions of the spec to get some new variety of functionality. (or at least it has a much much much better chance to – I’m sure there are some things out there that don’t actually put in fully compliant sockets, as the Dell’s of this world love their forced upgrade paths and obsolescence)
How long will the cables last?
I have not had a usb-c cable ‘die’ on me yet, but i have just had to keep buying new cables to do different things.
Like be longer than 3 feet, or have displayport alt mode work correctly, or charge and have usb 3.0.
I just kinda gave up and buy 3′ passive thunderbolt 3 cables now because they seem to have all of the wires and just work for everything I have needed so far, except for 100w charging.
That was another cable.
Also the spring contacts are in the usb-c plug and not socket, so theoretically the cable is supposed to be the replaceable part.
Unless you have a dock with an attached cable and then the entire thing is the replaceable part…
Yay for the environment.
Lucky you, I’ve only had one NOT die on me yet, and I’ve only had to use USB-C for about a year. Perhaps not helped because I only have a need for the full fat USB-C cables, with all the features… But in that year I’ve spent more on USB-C cables that break or never worked right despite claiming they should than I have on all the cables for anything else in two decades… Even the ‘budget’ USB-C cable is expensive, so when you only ever buy more premium end stuff as crap cables are never worth it, and they still turn out to be crap…
The cable is the replaceable part – until the constant plugging and unplugging of the cable rips the connector off from the PCB. The pins on the connectors are very tiny and held down by only slivers of solder.
The constant bending and twisting loads from mating the connectors will break them after a while, even on well designed devices with properly soldered connectors that are mechanically supported by the mechanical pins and clamped down by the enclosure (and many devices are not this well designed!). Leading to a device that refuses to charge, device that won’t talk to the computer and all sorts of such problems we know and hate.
And replacing/resoldering these connectors is certainly not an “user-serviceable” thing.
I’ve had to toss some I’ve used on my Galaxy S20. The connector gets loose then constantly makes/breaks connection for charging. So far the best I’ve found are Dewalt branded USB 2.0 A to USB C at Home depot. The USB 2.0 end is dual sided with a thin tongue in the middle that has contacts on both sides.
That should have been the Type A connector since USB 1.0!
To be fair, docks with attached cables are a USB-C exception, an exception made specifically so that docks can be made cheaply – they don’t have the extra circuitry needed (i.e. the mux, extra PD communications line processing, and VCONN) to add a socket to them. So, it makes sense that they’re a replaceable part – they’re there as a cheaper option.
For up to 60W charging and USB 2.0, any USB-C cable will do – so, for clarity, no need to use a thick cable with your phone or laptop charger day-to-day ;-P
I dont know, all this sounds way too complicated and complexity usually means vulnerabilities, problems that are horrible/impossibly to debug and so on. I mean USB is a great idea, but i think this went to far (too complex).
Indeed, it is a nightmare, and far to complex. USB really should have known better – USB1-USB2.0 largely won out over the technically vastly superior FireWire of their era because it was simple and cheap to make the devices. Now with USB-C, better hope you only really needed USB2.0..
It’s complicated, but in the same way that USB2 stack is complicated – something that people used to complain about, comparing it to LPT and COM. Some time later, USB2 has become a fixture of our lives =D
I finally got an Aukey CB-C35 USB C to 40 port USB 3.0 hub working with Windows. I had to use Snappy Driver Installer to find and download the drivers that would work with it since it’s supposedly a Mac only hub with a short captive cable.
However SDI still doesn’t have a “Billboard Device” drive in its database that supports the VGA port on the end of this triangular aluminum hub.
..40 port? o_o
I recommend looking up what “Billboard Device” stands for. It’s the “the USB-C port you’re using, doesn’t support all features of the device plugged in” device, and it’s there so that your OS can present a popup of “use a different USB-C port” to you. My bet is – your USB-C port doesn’t have DisplayPort support, since that’s what’s being used under the hood for HDMI and VGA ports on USB-C docks.
Even worse. I have a Dell Precision 7560. It needs not only one, but TWO USB-C connections to it’s docking station, and therefore also has two USB-C sockets. If you try to connect a USB-C charger to one of the sockets, regardless of how powerful, the notebook will always tell you that you can’t use it for charging.
I would’ve expected that the notebook would use at least the power the charger can provide, at least for charging the battery when the notebook is turned off, but it refuses to take any power at all from anything but it’s special Dell docking station.
This is incredibly dumb.
Also, the docking station has additional USB-C sockets, but those don’t do power delivery at all, they can only provide 5V.
Very poor, Dell, especially considering the price tag.
Those Precisions 7560 are pure crap, we have them at work. Plastic parts falls apart, motherboards and docks randomly die, those double USB-C docks randomly doesn’t connect one of those cables, or randomly have a problem with one of (only) three video ports and need to be physically disconnected from power + there are constant FW updates for both docks and laptops which only change the problemset do not shrink it.
From a technical perspective USB-C might be a great interface.
But it seems on the practical side the large majority of people have awful experiences with it. Maybe the USB consortium should actually listen to the users and try to address this issue.
Hey we keep expanding capabilities and making cables that physically look the same to the end user but are not compatible. Also the spec is so complex major companies screw up the standard. Oh and now your entire laptop is dependent on this single complex connector that cannot be repaired by your average repair shop. <- Maybe don't do all of this just a thought.
‘the large majority’ isn’t true – there’s so much USB-C tech quietly keeping on trucking out there at this point, and you never hear about it in ‘what’s wrong with USB-C’ discussions. With regards to connector complexity – people used to say the same about BGA and their soldering complexity, and now an average mainboard has 10 of them easily, we manage. There should be cable labels; also, using the cable included with the device will get you there.
talking about repair complexity.. It’s entirely possible to replace a USB-C connector, even with full 24-pins. Last summer, my friend’s Dell had a broken 24-pin USB-C connector, with ‘half of pads are SMD under the package’ deal. I replaced it in half an hour’s time, with nothing but a soldering iron, hot air gun, and some flux. Repair shops that can’t do the same, have no excuse – and if your shop can’t do it, find a better shop. Also, just as a warning for something I see happen – don’t judge repair shops by hobbyists’ skill level. I did laptop repair for a good few years, and I can assure you that a hobbyist doesn’t have repair shop skills, and vice-versa. Repair shops can replace BGAs quite easily, but don’t know how to work with I2C.
The actual problem can be sourcing replacement connectors – not all companies use standardized ones. That said, a) this is right-to-repair territory at this point, b) this was the same for MicroUSB.
When I first saw the USB-C connector pin-out, I assumed that no muxes would be needed. Assuming that all 4 tx/rx pairs were present, all you’d need to do to accommodate the plug rotation would be to change the identity of the pairs, which you could do logically instead of physically. I suppose the need for muxes is in the apparently more-common case of all 4 tx/rx pairs not being present.
Nope, all 4 pairs are supposed to be present in all high-speed (more than USB 2.0) cables. The muxes are there to handle cable rotation and the resulting swapping of pairs, since interfaces like DisplayPort and USB3 don’t support that natively. A mux takes USB-C connector high-speed pins with USB3 or DisplayPort on them, and interfaces them to actual USB3 or DisplayPort signals on your CPU/device/etc.
I wasn’t referring to the cables; I meant to say in the end-point hardware (USB3 chips). If you’re always connecting the 4 pairs to each other, then it seems like the pairs could just be logically flipped based on the rotation-detection pins. But I guess since the initial end-point chip would eventually have to talk to another chip (since as an HDMI transmitter), that effectively makes the end-point chip a mux.
Yeah the ‘logically flipped’ is the part that a mux deals with. Some chips do indeed have a mux built in, ie Thunderbolt ones! However, not all do, and it makes sense to offload it.