[HN Gopher] USB Cheat Sheet ___________________________________________________________________ USB Cheat Sheet Author : WithinReason Score : 308 points Date : 2022-05-05 08:43 UTC (14 hours ago) (HTM) web link (fabiensanglard.net) (TXT) w3m dump (fabiensanglard.net) | synergy20 wrote: | Like the simple site design with a one page info about USB. | | someone please make similar one-page with tables about PCI | Express, Ethernet, HDMI... | NoXero wrote: | I second that request! | ProZsolt wrote: | I created a cheat sheet for Ethernet, when I built my home | network: | https://github.com/ProZsolt/runbook/blob/master/ethernet-cab... | synergy20 wrote: | shoud 100, 400, 800G be added, yes a bit earlier for 800G but | I think 100/400G are already in use at data centers. | ProZsolt wrote: | This only covers twisted pair, as I only use this as | reference when I need new endpoints in my or my parents | house. | | I'll update the guide when I rewire my house with fiber | optics (currently I don't even use the full potential of | cat 6), but contributions are welcomed. | navaati wrote: | Really nice ! | | Today I learn that there is a 25 and 40G-BASE-T on copper, | these PHY must heat like hell haha. | dschuetz wrote: | So where exactly does USB-C fall into? | | I have 2 different generations of USB-C hosts, and they behave | quite differently when approaching max cap, especially with high- | quality low-latency audio (USB-C was supposed to be de-facto | replacement for FireWire). | Tepix wrote: | Good question. I bought a RaidSonic Icy Box IB-1121-C31 USB 3.1 | (10Gbit) S-ATA dock recently (with a USB Type C connector) that | came with a USB C cable and had a buy a special "USB-A - USB | type C cable" to achieve 10Gbit/s with the 10GBit/s USB A | connector of my mainboard. | | The "USB A - USB type C cables" that i had already only worked | up to 480MBit/s. | hyperman1 wrote: | It's orthogonal. | | Usb A is a host side connection Usb B (normal/mini/micro) is a | client side connector Usb C is a 2 way connector. | | Each of them can be implemented for each USB version, except | USB C came later and makes no sense befor USB 3. | | Then USB versions added features, signalling conventions and | wires. But the USB A and B connector are backward compatible | all the way to USB 1.0 1.5Mbit/s | kevin_thibedeau wrote: | On-the-Go allows mini and micro B to be host as well. | LeonidasXIV wrote: | USB-C is a connector type, like USB-A (usually known as the | classic USB plug) and USB-B (usually the other side of said | plug, a square kind of connector). USB-B had other offspring | like miniUSB and microUSB (note that in these cases on the | other side of the cable you usually have a USB-A plug). | | USB-C is the first time cables have the same connector on both | sides, so it obsoletes USB-A and USB-B. But what is sent over | USB-C? Can be USB 3 with which it is often conflated because | they came around the same time, but it can also be USB 2, so it | is a bit hard to tell. But USB 3 can use old style USB-A as | well (the blue plugs with the same shape as the classic USB | plugs) and USB-C (the microUSB plugs with an extension off to | the side). | LordDragonfang wrote: | >note that in these cases on the other side of the cable you | usually have a USB-A plug | | Usually a _full-size_ USB-A, you mean, because what we | commonly know as mini-USB and micro-USB are actually mini-B | and micro-B, which have corresponding (but now rarely used) | micro-A and micro-A ports. Before USB-OTG, USB used to be an | explicitly directional protocol, with a master and a slave | device. | | https://upload.wikimedia.org/wikipedia/commons/8/82/USB_2.0_. | .. | | https://en.wikipedia.org/wiki/USB_hardware | danieldk wrote: | _Can be USB 3 [...] USB 2, so it is a bit hard to tell._ | | ...or Thunderbolt, USB 4, DisplayPort (through Alt-mode or | encapsulated in Thunderbolt), or HDMI (Alt-mode), or MHL | (Alt-mode), USB Power Delivery... | | Unfortunately, not every cable with USB-C connectors can | carry all of these. E.g. there are USB-C cables that can only | carry USB 2. Or cables that can carry USB 3, but not | Thunderbolt. Also, not all cables can carry the same wattage | for power delivery. | | It's a mess. | jasomill wrote: | Worse, there are no "best" cables longer than 0.5m: any | longer than that, Thunderbolt 3 requires active cables | which don't pass non-Thunderbolt data beyond, IIRC, 480 | Mbps. | | As someone who spent many years using a mix of | 25/50/68/80-pin fast/ultra/... single-ended, LVD and HVD | parallel SCSI devices, however, USB-C/Thunderbolt cabling | _still_ feels like a breath of fresh air. | danieldk wrote: | I think Thunderbolt 4 active cables are supposed to pass | higher USB 3 speeds? At least the Apple Thunderbolt 4 | cable claims to do so: | | https://www.apple.com/shop/product/MN713AM/A/thunderbolt- | 4-p... | nolok wrote: | There was a period of time where a google engineer was | producting review on amazon about which usb-c cable would | make your laptop burn. That was fun, and totally not the | sign of an overbloated standard. | cesarb wrote: | IIRC, that particular cable was one which had its power | wired to the ground pin and ground wired to the power | pin. No standard can help you if the cable is that badly | made. | | (The effect of that miswiring is to apply a negative | voltage, around -5V, to a chip most probably designed for | a range of -0.5V to 20.5V; which results in a short | circuit through at least the ESD protection diodes within | the chip, and possibly other parts of the chip too.) | Dylan16807 wrote: | Yep, a batch of cables having the super basic power pins | wired backwards tells you basically nothing about the | standard, no matter how often people try to use it as | evidence of complication. | | And the docks that were frying switches were putting 9 | volts on a signal pin, also obviously wrong. | rob74 wrote: | Of course USB-C makes this worse, but the problem already | started earlier: a few years ago I connected my phone to my | computer with a USB-A to micro USB cable and was scratching | my head why it didn't work. Then I remembered that the | cable had come with some Bluetooth headphones and was only | a charging cable without data lines... | colejohnson66 wrote: | Desktop speakers do this still. Instead of simply being a | USB speaker set, they use the line out jack for audio and | a USB plug for power. | LordDragonfang wrote: | There's actually a reason for that. Standard USB can | (obviously) only transfer digital audio, and most | speakers are "dumb" devices designed to just amplify an | analog signal. In order to convert digital to analog, you | need a DAC (Digital-to-Analog-Converter), and good DACs | are still a nontrivial cost to a manufacturer, so | whatever DAC you already have in your computer is | probably better than the crappy one that would come with | cheap consumer speakers. | izacus wrote: | Funny enough, USB-C can transport analogue audio over USB | cable though :) | | Tends to be too expensive for the cheapest of products. | willis936 wrote: | USB 4 AKA USB 4 Gen2x2 | | USB 4 (opt) AKA USB 4 Gen3x2 | | They had a chance to fix their colossal fuckup and they decided | not to. | ThreePinkApples wrote: | In marketing and on cables they've chosen to use the terms USB4 | 20Gbps and USB4 40Gbps, so at least that's explicit. There's | also officials ways to mark cables as being 100W or 240W | capable. | nolok wrote: | Their issue was not the naming for consumer or tech user, their | issue was "how do we allow any random laptop from claiming | latest usb despite not actually supporting it". | | It was super obvious with usb 3 and its sub versions, and it | gets even worse with 4. | paulmd wrote: | Yes. The "IF" in "USB-IF" stands for _implementers forum_ , | it is a consortium of hardware companies who make devices. | It's preferable to them if they can slap "USB 3.2 support!" | on the box without having to redo their boards with a new, | expensive component. | | In other words, the incentives here are for USB-IF to | _promote_ customer confusion, not to _reduce_ it, because | that confusion can sell devices and push profit margins. | | It's absolutely terrible that the EU is giving this group a | legal monopoly on the ability to create and proliferate new | standards. Their incentives fundamentally run against the | consumer and they have repeatedly acted against the interests | of the consumer. Unlike HDMI, there is no VESA to | counterbalance them, it is USB or nothing, so you'll have to | deal with these crappy standards going forward. | | -- | | HDMI is doing something similar now too - "HDMI 2.1" is a | completely hollow standard where every single feature and | signaling mode added since HDMI 2.0 is completely optional. | You can take HDMI 2.0 hardware and get it recertified as HDMI | 2.1 without any changes - actually you _must_ do this since | HDMI Forum is not issuing HDMI 2.0 certifications any more, | only HDMI 2.1 going forward, the new standard "supercedes" | the old one entirely. | | So - "HDMI 2.1" on the box doesn't mean 4K120 support, it | doesn't mean VRR support, it doesn't mean HDR support. It | could actually just literally be HDMI 2.0 hardware inside. | You need to look for specific feature keywords if that is | your goal. | | https://arstechnica.com/gadgets/2021/12/the-hdmi-forum- | follo... | | https://www.youtube.com/watch?v=qo9Y7AMPn00 | hdjjhhvvhga wrote: | If you think it's not complicated enough, add Thunderbolt to it. | CharlesW wrote: | Thunderbolt 4 is effectively USB 4. | https://www.cablematters.com/blog/Thunderbolt/usb4-vs-thunde... | netsharc wrote: | Ah USB. In the old days it was different cables for different | things, nowadays it's 1 connector for everything but beware, the | cable might physically plug into the socket, but whether you'll | get the functionality you want? | izacus wrote: | Just how many devices do you meet that regularly hit those edge | cases? Outside 4K+ multimonitor connections? | | (It's really popular and easy to bash on USB on this forum, but | it turns out that in real life your USB-C device will "just | work" for pretty much all setups outside really fringe high | performance ones. And even those will usually just negotiate | lower rate.) | doubled112 wrote: | Seems it is going backward to me too. | | At one point I remember hooking up a computer being like one of | those shape puzzles we give children. If you can match them | they'll work. No two of my devices used the same cable or port, | but if it fit it'd work. | | Keyboard switched to PS/2 so those and PS/2 mice were | confusing, but eventually they standardized on colours. | | USB came out and you could just plug it in wherever. This was | great. | | And now? 20 combinations of cable features with the same socket | but all do something else. I can only imagine what the return | rate will be for stuff like this. | cosmotic wrote: | Where's the standard speed? | can16358p wrote: | So on the next versions of USB, the cable length will get shorter | and shorter until the max gets to 5cm? | | While I get the technical reasoning about high | frequency/attenuation etc that limits cable length as speeds go | higher, there are obviously some practical limits to how short | cables can be. | | How would that be solved, I don't know. | moffkalast wrote: | Keep the same speeds, add more wires. | [deleted] | CoastalCoder wrote: | Not my area of expertise, but maybe some (unrealistic) options | include using fiber optics for the data lines, or adding more | data lines. | birktj wrote: | There already exists some fiber-optic USB cables that come in | lengths >50m and with support for USB 3.1 so it doesn't seem | like a very unrealistic option. | Chilinot wrote: | That sounds more like fiber optic adapters/converters that | fit into usb-ports and talk usb, rather than USB-cables | that can be 50+ meters. | Dylan16807 wrote: | What's the difference between talking USB and being USB? | duskwuff wrote: | Some USB4 / Thunderbolt cables are like that, but with | copper in the middle. The drivers on the device end | wouldn't be able to maintain signal integrity over that | size of cable, so there's a pair of transceivers in each | end of the cable to convert the signal into a format | that'll survive transmission. | michaelt wrote: | https://www.amazon.com/FIBBR-Female-Active-Extension- | Optical... provides USB-to-fibre-to-USB in a single | cable, and a copper pair in parallel for power. | jayd16 wrote: | Seems like you can get 3m optical usb-c cables. Oculus | sells an official "Full featured USB active optical | cable. USB 3.2 Gen 1 Type-C" for tethered play. | | That's what the cheatsheet says so maybe that's part of | the spec. | jsjohnst wrote: | I think GP is thinking of fiber optic Thunderbolt cables | probably. | BolexNOLA wrote: | Redmere chips also proved HDMI can go very, very far with a | little extra investment. I've run 4K signals hundreds of | feet with them. We've seen this problem solved several | times, I can't imagine it's physically impossible with | USB-C. | dual_dingo wrote: | I guess at some point optical will be the only way forward. | | Having more data lines in a serial bus is interesting, as the | whole reasoning to go from parallel lines (e.g. Centronics, | ATA/SCSI or ISA/PCI buses) to serial (SATA/SAS, PCIe, USB) | was that coordinating multiple data lines got impossible due | to physical limitations where e.g. minimal differences in | cable lengths started to matter). | Dylan16807 wrote: | > I guess at some point optical will be the only way | forward. | | Maybe. Though Infiniband's currently at 100Gbps per lane on | a 1.5 meter passive cable. And active cables can give you a | moderate boost while still on copper. | paulmd wrote: | that's a giant QSFP+ cable (I think mine are at least | 3/8") with tons of shielding and a terrible bend radius | though. | | And my cables all have a "10 plug/unplug cycle lifespan" | sticker on them - it undoubtedly will go for longer in | practice but it's not designed for USB-style usage where | you might plug and unplug your phone a dozen times a day | as you charge it. | | Commercial design concerns are very different from | consumer design concerns, basically. Phones would | probably be easier if we had a 1/2" x 1/2" x 1.5" | connector with a shielded connector body! ;) | helpm33 wrote: | Multiple serial busses, each with its own clocking and | buffer, so that the combined data is extracted | synchronously at the end. The crosstalk is still a problem | but there are ways around that: different twist rates for | different pairs for instance. | legalcorrection wrote: | Suggestion: maybe include all the USB-C-plug Thunderbolt versions | too. My personal policy these days is to just buy reputable | Thunderbolt cables for all my USB-C needs. Maybe I'm doing the | wrong thing? | | Also, I think there's a difference between active and passive | USB-C cables, or something like that. | masklinn wrote: | > Maybe I'm doing the wrong thing? | | If you're happy with it then probably not. | | The main possible issues are that it's more expensive and you | get shorter and thicker (less flexible) cables, a passive non- | optical TB (or USB4) cable will top out around 1m. | | Less capable cables can be longer and thinner which is | convenient for e.g. mice and such small devices. But otherwise | may not matter overly much. | moron4hire wrote: | I've been pretty happy with my less flexible cables. I don't | need to snake them around tight corners anywhere. Being less | flexible seems to keep them from auto-tangling. | masklinn wrote: | Some of the entries seem incorrect: "USB 3.2 (USB 3.2 Gen 2x2) | and "USB 4" (USB 4 USB4 Gen 2x2) should have the same nominal | data rate of 2500MB/s, they're 2 lanes (x2) of 10GB/s. Though | they are apparently coded differently electrically, so they're | distinct protocols. | | The tables would benefit from mentioning the coding (8/10 or | 128/132) as IMO it's one of the most confusing bits when you see | the _effective_ data rates: | | * USB 3.2 Gen 1x2 has a nominal data rate of 10G (2 lanes at 5G) | with a raw throughput of 1GB/s (effective data rates topping out | around 900MB/s) | | * USB 3.2 Gen 2x1 has the same nominal data rate of 10G (1 lane | at 10G) but a raw throughput of 1.2GB/s (and effective data rates | topping out around 1.1GB/s) | | The difference is that Gen 1x uses the "legacy" 8/10 encoding, | while Gen 2x uses the newer 128/132 encoding, and thus has a much | lower overhead (around 3%, versus 20). | belter wrote: | Also should be: | | 12 Mbps -> 1.43 MiB/s -> 1.5 MB/s | | 480 Mbps -> 57 MiB/s -> 60 MB/s | | 5000 Mbps (5 Gbps) -> 596 MiB/s -> 625 MB/s | | 10000 Mbps (10 Gbps) -> 1192 MiB/s -> 1250 MB/s | | 20000 Mbps (20 Gbps) -> 2384 MiB/s -> 2500 MB/s | | 40000 Mbps (40 Gbps) -> 4768 MiB/s -> 5000 MB/s | adrian_b wrote: | No, some of your rates are wrong. | | The so-called 5 Gb/s USB has a data rate of 4 Gb/s. | | The marketing data rates for Ethernet are true, i.e. 1 Gb/s | Ethernet has a 1 Gb/s data rate, but a 1.25 Gb/s encoded bit | rate over the cable. | | The marketing data rates for the first 2 generations of PCIe, | for all 3 generations of SATA, and for USB 3.0 a.k.a. "Gen 1" | of later standards, are false, being advertised as larger | with 25% (because 8 data bits are encoded into 10 bits sent | over the wire, which does not matter for the user). | | All these misleading marketing data rates have been | introduced by Intel, who did not follow the rules used in | vendor-neutral standards, like Ethernet. | | So PCIe 1 is 2 Gb/s, PCIe 2 & USB 3.0 are 4 Gb/s and SATA 3 | is 4.8 Gb/s. | | So USB "5 Gbps" => 500 MB/s (not 625 MB/s), and after | accounting for protocols like "USB Attached SCSI Protocol", | the maximum speed that one can see for an USB SSD on a "5 | Gbps" port is between 400 MB/s and 450 MB/s. | | The same applies for a USB Type C with 2 x 5 Gb/s links. | | As other posters have already mentioned, USB 3.1 a.k.a. the | "Gen 2" of later standards has introduced a more efficient | encoding, so its speed is approximately 10 Gb/s. | | The "10 Gbps" USB is not twice faster than the "5 Gbps" USB, | it is 2.5 times faster, and this is important to know. | fabiensanglard wrote: | I should add Nominal vs Raw vs Effective speed to the | table. | | Can you confirm with the rule to be used. | | Raw Speed = Nominal / Encoding | | UMS Speed = Raw / UMS overhead | | In the case of 3.0 that would be: | | Nominal = 625 MiB/s | | Raw = 625 - 20% = 500 MiB/s | | UMS = 500 - 20% = 400 MiB/s | adrian_b wrote: | The names for the various bit rates vary between authors | and standards. | | I believe that the least confusing names would be: | | Data bit rate = the rate at which the data bits provided | by the user are sent | | Signaling bit rate = the rate at which bits are sent over | the physical communication medium | | The 2 rates are not the same because the user data bits | are encoded in some way before being sent. The signaling | bit rate does not have any importance, except for those | who design communication equipment. For the users of some | communication equipment, only the data bit rate matters. | | The data bit rate is equal to the signaling bit rate | multiplied by the ratio between data bits and the | corresponding encoded bits. | | For example, for USB 3.0 (single link Gen 1): | | Signaling bit rate = 5 Gb/s | | Data bit rate = (5 * 8 / 10) Gb/s = 4 Gb/s | | Data byte rate = (4 / 8) GB/s = 500 MB/s = 477 MiB/s | | 5 Gb/s corresponds to 625 MB/s, but for a signaling bit | rate it is completely useless to convert bits to bytes, | because groups of 8 bits on the physical communication | medium do not normally correspond to bytes from the data | provided by the user. Only for the data bit rate it is | meaningful to be converted to a data byte rate. | | For USB 3.1 (single link Gen 2): | | Signaling bit rate = 10 Gb/s | | Data bit rate = (10 * 128 / 132) Gb/s = 9.7 Gb/s | | Data byte rate = (9.7 / 8) GB/s = 1212 MB/s = 1156 MiB/s | jbverschoor wrote: | Is that the same intel that "forgot" to mention that they | overclocked a demo cpu and used ndustrial water chiller? | ridgered4 wrote: | My favorite is when Intel demoed the new ivybridge iGPU | by having a guy fire up VLC player to play some footage | of a racing game while he pretended to control it with a | steering wheel controller. | | I looked this up and it's actually even worse than than I | thought. When called out he claimed it was being control | from backstage. | | https://www.techpowerup.com/158448/that-dodgy-intel-ivy- | brid... | asciii wrote: | I was curious and went looking for it. That's pretty | hilarious oversight! | | https://www.tomshardware.com/news/intel-28-core- | cpu-5ghz,372... | jbverschoor wrote: | Lol that's hilarious | CamperBob2 wrote: | He goes off the rails earlier than that, by saying that USB 2.0 | is "also known as" Hi-speed. HS is only one data rate supported | by the USB 2.0 standard; it incorporates both full speed from | the earlier standard and low speed, which isn't mentioned at | all. | masklinn wrote: | That's more of an approximation matching how, frankly, most | people think of the specs: yes USB 2.0 supersedes 1.1 | entirely, but everyone will think of "full speed" and "low | speed" as USB 1 which are BC supported by USB 2.0. | | That's also why USB 3.1 and 3.2's rebranding of previous | versions is so confusing and a pain in the ass to keep | straight: USB 3.2 1x1 is USB 3.1 Gen 1 is USB 3.0 (ignoring | the USB 2.0 BC). | [deleted] | fabiensanglard wrote: | Thank you for noticing these issues, I have updated the table. | | I would be happy to improve it and add encoding. I am surprised | by some of the summary entries on Wikipedia | (https://en.wikipedia.org/wiki/USB4). Looks like USB4 | "reverted" to 128b/132b. It is accurate? | lxgr wrote: | 128b/132b is the more efficient coding. The closer to 1 the | fraction is, the less coding overhead it has, and 128/132 is | larger than 8/10. | fabiensanglard wrote: | Actually, I just noticed that 128/132 is the same fraction | as 66/64 so both scheme has the same encoding efficiency. | So USB-4 did no "revert in terms of efficiency. | 0xTJ wrote: | Just how much do you have to hate consumers to come up with a | scheme like this? Increment revisions as you add more features, | add something to the end to say how fast it goes. The 3.2 | renaming is idiotic. | Villodre wrote: | I'm always flabbergasted at how difficult and hostile to the user | is discern between the various USB standards. | markus_zhang wrote: | Is that year 2025... | a3w wrote: | Nope, USB4 has been defined for a while now. | cesaref wrote: | There's something about the naming of USB that is great. I love | how there are now something like a dozen 'universal' standards, | and how the serial bus now has multiple lanes. | moffkalast wrote: | All it's missing is the pinouts and the charger resistor divider | setup definitions. | dimman wrote: | Thanks. Nit-picking here but ground is usually abbreviated GND, | not GRD. | Aragorn2331 wrote: | Hello Fabien ! I saw on twitter that you had built a gaming | setup, can you write an article on your blog as you did for your | silent pc ? | fabiensanglard wrote: | I did build a PC last year especially to play Diablo2: | Ressurected. I did write something at the time but never | published it. Maybe I will clean it up. | Someone wrote: | No USB On-The-Go (https://en.wikipedia.org/wiki/USB_On-The-Go) or | Wireless USB (https://en.wikipedia.org/wiki/Wireless_USB)? | | USB is a triumph of marketeers over engineers. All these things | are called USB because USB sells (see also: Bluetooth). | ChrisRR wrote: | Bluetooth Smart aka. Bluetooth Low Energy aka. Wibree aka. not | actually bluetooth | IshKebab wrote: | I don't know anything about wireless USB but USB OTG is called | USB because it _is_ USB. It 's not some totally unrelated | protocol. | jandrese wrote: | I thought OTG was just changing up where the host controller | is sitting in the USB relationship? So you can have a device | that acts like a client when hooked to a computer, or a | master when hooked to a thumb drive/webcam/etc...? | IshKebab wrote: | Yeah it just allows you to use a B port as a host (if | supported). It's still the USB protocol. | cesarb wrote: | AFAIK, according to the standard you still cannot use the | B port as a host, it should instead be an AB port (a | socket in which both A and B plugs fit). | paulmd wrote: | I had an iRiver H320 with USB-OTG support. At the time I | thought it was just a straight-up mini-B port but you're | right, that's actually a mini-AB port! | | https://www.guru3d.com/miraserver/images/reviews/soundcar | ds/... | | I am not sure I have ever seen mini-A anywhere. | | God, what a wacky standard. (USB-OTG specifically but | really USB plugs in general) | jcrawfordor wrote: | Another example of mini-AB is the TI-84 series. Two | calculators can be directly connected but a USB A-A cable | is verboten by the spec (although I sometimes see them | nonetheless), so TI put an AB port on the calculator and | sold a mini-A to mini-B cable. It is somewhat confusing | to users that a cable with two different ends was | nonetheless completely transposable. | | I'm not sure of this at all but I sort of doubt the TI-84 | used spec compliant OTG, because in general the USB | implementation on that calculator was very weird and | unreliable and gave the feeling that they were doing | something uncouth like bit-banging and not quite fast | enough. I remember it routinely taking multiple attempts | to get something to transfer successfully. | thatfunkymunki wrote: | i cannot find any examples of this kind of port, can you | share a link? | paulmd wrote: | iriver h320 | | https://www.guru3d.com/miraserver/images/reviews/soundcar | ds/... | jandrese wrote: | It is one of these connectors: | | https://en.wikipedia.org/wiki/USB_hardware#USB_On-The- | Go_con... | | But every OTG device I have ever used has just used the | USB-A port. | [deleted] | _joel wrote: | I've definitely used 5m+ extensions on USB1 (and 2 iirc) before. | I guess it'd be sketchy running something that requires decent | throughput and not b0rk on ECC/FEC/whatever it uses but for | temperature sensors which I was using, it was fine. | TonyTrapp wrote: | A long time ago, I was using a USB 1 or 2 Wifi adapter through | a USB extension cord, I'm pretty sure the total cable length | was more than 5 meters. It "worked", but even just flicking a | light switch caused the network connection to reset. So yeah, | it may "work", for certain values of "work". | Lucasoato wrote: | Why didn't they focus enough on cable length? I'm not sure about | how much latency they would add since the current is still | traveling at light speed. | | Maybe there's someone in the world wondering if it's possible to | emulate MarioKart from his office PC to the living room with a | 10m HDMI and USB3 cable... Just guessing :) | IvanK_net wrote: | Fun fact: USB 2.0 webcams have been existing for over 10 years. | USB 2.0 is 60 MB/s. | | A pixel of an image is 3 Bytes. A 1920x1080 FullHD image is 6.2 | MB. At 30 frames per second, second of a FullHD video is 186 MB. | How did they do that? | | Answer: frames are transferred as JPEG files. Even a cheap $15 | webcam is a tiny computer (with a CPU, RAM, etc), which runs a | JPEG encoder program. | pseudosavant wrote: | Most webcams, especially 10 years ago are not 1080p, or even | 60fps. Many aren't even 720p. 1280 x 720 x 3 bytes x 30 fps = | ~80MB/second. 480p @ 30 fps = 26MB. That is how many webcams | can get by without hardware JPEG/H264 encoding. | | 4K @ 60fps = 1.4GB/sec. USB 3, even with 2 lanes, will have | trouble with that. | grishka wrote: | Hm. But then wouldn't it make more sense to just stream the raw | sensor data, which is 1 byte per pixel (or up to 12 bits if you | want to get fancy), and then demosaic it on the host? Full HD | at 30 fps would be 59.33 MB/s, barely but still fitting into | that limit. | | But then also I think some webcams use H264? I remember reading | that somewhere. | BayAreaEscapee wrote: | I don't know where you get "1 byte per pixel" from. At | minimum, raw 4:2:0 video would be two bytes per pixel, and | RGB would be three bytes per pixel with 8-bit color depth. | Dylan16807 wrote: | When talking about digital cameras, each "pixel" is a | single color sensor. Blame marketing. | | Also 4:2:0 is 6 values per 4 pixels. 1.5 bytes per pixel at | 8-bit. | nybble41 wrote: | You're talking about processed color frames. The GP was | suggesting that the camera stream the raw sensor data, | which doesn't have individual color channels, just a | monochrome grid with 10 or 12 bits of usable data per | pixel. A bayer filter[0] is placed in front of the sensor | so that a given color of light falls on each cell. The USB | host would be responsible for applying a demosaicing[0] | algorithm to create the color channels from the raw sensor | data. | | If we take the AR0330 sensor used in the USB Camera C1[2] | as an example, it has a native resolution of 2304H x 1296V | and outputs 10 bits per native pixel after internal A-Law | compression[3] for a total raw frame size of 3.56 MiB, | assuming optimal packing. The corresponding image, | demosaiced and downscaled to Full HD (1920x1080), in RGB | with eight bits per channel would be 5.93 MiB. | | [0] https://en.wikipedia.org/wiki/Bayer_filter | | [1] https://en.wikipedia.org/wiki/Demosaicing | | [2] https://www.kurokesu.com/shop/cameras/CAMUSB1 | | [3] https://www.onsemi.com/products/sensors/image- | sensors/ar0330 | masklinn wrote: | > it has a native resolution of 2304H x 1296V | | Seems to me like that kills the idea dead? GGP assumed | 8bpp and that the raw resolution matched the output, and | came out... well wrong (the effective bulk transfer rate | of USB 2.0 is 53MB/s on a good day), but by just a few | megs. | | However the raw resolution is 40% higher than the final | output, meaning even at 8bpp you're at 85MB/s and you've | blown way past any hope of recovering via a few tricks. | At 10 bpp you're above 100MB/s. | nybble41 wrote: | Native resolution at 10bpp requires 40% less data per | frame than the final Full HD RGB output at 8bpp per | channel (24bpp total), so it would represent some | savings. | | The problem is that neither format fits within the limits | of USB 2.0 at 15 FPS or higher. To achieve a reasonable | framerate you need to apply compression, and generally | speaking you'll get better compression if you demosaic | first. | monocasa wrote: | The pixel density doesn't generally refer to the density of | the Bayer pattern, which can be even denser. Generally a | cluster of four Bayer pixels makes up one pixel (RG/GB), but | like most things in computing, the cognitive complexity is | borderline fractal and this is a massive simplification. | Dylan16807 wrote: | > Full HD at 30 fps would be 59.33 MB/s, barely but still | fitting into that limit. | | That limit is too high even as a theoretical max. | | You _could_ do raw 720p. | masklinn wrote: | > Full HD at 30 fps would be 59.33 MB/s, barely but still | fitting into that limit. | | It's not fitting into anything I fear, best case scenario the | _effective_ bulk transfer rate of USB2 is 53MB /s. | | 60 is the signaling rate, but that doesn't account for the | framing or the packet overhead. | verall wrote: | It would need a funny driver and since that stuff is big | parallel image processing it's easy in HW but if someone has | a netbook or cheap/old Celeron crap it would peg their CPU to | do the demosaic and color correction. | kevin_thibedeau wrote: | The cheap ones are using hardware JPEG encoders. The associated | micro isn't powerful enough to do it in firmware alone. | masklinn wrote: | Surprised they don't use a hardware video encoder, is it | because the well and efficiently supported formats are all | MPEG, and thus have fairly high licensing cost on top of the | hardware? Or because even efficient HVEs use more resources | than webcams can afford? Or because inter-frame coding | requires more storage, which (again) means higher costs, | which (again) eats into the margin, which cheap webcam | manufacturers consider not worth the investment? | izacus wrote: | MJPEG is just a very simple "video" format that needs very | simple and cheap electronics to work. Video encoding blocks | are mostly part of bigger SoCs and comes with licensing | costs. | | Same goes on the other hand for the receiving end - | decoding a stream of JPEGs is just much simpler in both CPU | use and code complexity than dealing with something like | H.264. | martinmunk wrote: | My older Logitech C920 has an on-board H.264 encoder. Newer | revisions of the same model does not. | | I haven't figured out why they chose to remove it, but your | point about licensing cost combined with them not | advertising it much as a feature, and most of their | competitors not including "proper" video encoding might | explain it. | | Edit: Found an official explanation here: | https://www.logitech.com/en-us/video- | collaboration/resources... TLDR, they figure most computers | at that point had HW encoders. | lxgr wrote: | Unfortunately, this makes it much harder to use these as | webcams on a Raspberry Pi (which even has H.264 hardware | acceleration - the bottleneck is decoding the MJPEG | stream from the camera, for which ffmpeg does not have | hardware acceleration on the RPi). | broomhall wrote: | As an alternative to ffmpeg, GStreamer provides hardware | accelerated MJPEG decoding on the Pi. I think there are | bugs, though, which makes it unsuitable for some use | cases. Here's an example pipeline - https://forums.raspbe | rrypi.com/viewtopic.php?p=1989575#p1989... | verall wrote: | It needs a uC with some special hardware anyways to do demosaic | or else it would require special drivers that would peg some | people's crappy laptop CPUs. | | Also the raw YUV 4:2:0 is 1.5 bytes per pixel so that's doing | half of the "compression" work for you. | JoeDaDude wrote: | If only it included a guide to the different USB connectors, but | that might make TFA too long to publish. | eugene3306 wrote: | just curious. Can USB3 work without D+ and D- ? | [deleted] | formerly_proven wrote: | USB 3 and previous standards are completely separate | connections and software stacks - the USB 1/2 D+/D- pair does | not interact at all with SSRX/SSTX. You should be able to | literally cut the D+/D- wires in an USB 3 cable and it should | still work as a USB 3 cable. | kevin_thibedeau wrote: | I doubt any normal hosts will enumerate a USB device without | the USB 2 data lines. PD will definitely not work. You might | be able to get an alt mode running. | cesarb wrote: | They probably would enumerate just fine, because the | SuperSpeed enumeration is completely independent from the | USB 2.x enumeration. USB-PD uses a separate pin/wire, not | the USB 2.x D-/D+ pair, and you cannot get an alt mode | running (except the special analog audio and debug | accessory modes) if USB-PD doesn't work, since alt mode | enumeration goes on top of USB-PD. | stavros wrote: | What does the U in USB stand for again? | jbverschoor wrote: | Actually, I think it's just a upside down "[?]". Makes sense | because the non-C connectors are always upside down, and all it | does is intersect wires. | theandrewbailey wrote: | Unintuitive. | _joel wrote: | Unintelligable | notorandit wrote: | Uikipedia | jbverschoor wrote: | U-turn | Kab1r wrote: | USB versioning is such a clusterfuck. | 411111111111111 wrote: | There was a really short timeframe when I was really positive | about USB, but that has been long lost since. | | They should've never allowed cables to only provide some | capabilities and still get the branding. Having capabilities | for connectors was fine imo, but also accepting them with | cables was bad because you cannot really find out what it | supports and where the issue originates of something goes wrong | jsjohnst wrote: | It's why I always buy TB3 (or now TB4) cables rather than a | cheaper USB-C to USB-C. Due to the strict requirements on TB | cables, you can pretty much guarantee it'll support any use | case (alt modes, PD, etc). Sometimes overspending is worth | the headache prevention. | jbverschoor wrote: | Apple just released a EUR159 cable | paulmd wrote: | 3m is beyond the max cable length specified by | Thunderbolt, so it requires active extenders (they're | hidden in the plugs) and tight manufacturing and | shielding. You're paying extra for the ability to break | that max length spec, and it's one of only a handful of | products that do it. | | The only other one I'm aware of is the Corning Active | Optical Cable series which costs $360 for a 10m | Thunderbolt 3 cable or $479 for a 30m cable, or $215 for | a 10m Thunderbolt 2 cable (ie slower and different | connector, potentially needs a $50 converter on each | end). Also those Corning cables have a reputation for | failing _barely_ out of warranty even if they are treated | very delicately. Amazon reviews are _full_ of "my cable | failed 1 year and 1 month after purchase and Corning told | me to go eat a dick" type reviews. | | https://www.bhphotovideo.com/c/product/1577008-REG/optica | l_c... | | Also, just FYI, but max length spec on a USB 4 cable | (which will support Thunderbolt-like features) is 0.8m | and you'll need to use special cables to get the full | capabilities there too, you can't just use a $15 usb-c to | usb-c cable you bought off amazon. Just like some usb-c | cables only support usb 2.0 speeds, you won't get full- | duplex 40gbps signaling out of a 10gbps half-duplex USB | 3.1 cable. USB certification isn't magic, these are | physics-based electrical/RF problems here and high- | capability cables/devices require more expensive | implementations. | | But anyway go ahead and click through that B+H link and | look through their thunderbolt 3 cable category for | another 3-meter cable. You won't find any. If 2 meters is | not enough... your options are Apple, Corning, or | nothing. | | The Apple premium is still a thing, but I'd expect | competitors to clock in around $100 if/when they come | out. There is always a steep price inflection once you | move from passive cables to active cables or fiber. If | you can avoid that, great, use a shorter cable. If you | can't, you have to pay up. Not everyone can just move | everything closer (eg running through walls) and it's | always so disappointing to see people arguing _against | consumers having options_ just because they don 't | personally need them. No one is making you buy this, but | the people who do now have an option they didn't before. | That "if I'm not interested in a product then it | shouldn't exist at all!" mindset seems to be extremely | pervasive in the tech space and I just don't get it, not | every product has to be aimed at you personally. It's | "center of the universe syndrome" as one of my teachers | liked to call it. | | I've looked at the Corning cables for setting up a Vive | Wireless Adapter that can be in a different room from my | desktop rig (adapter goes in a Thunderbolt enclosure, | mounted on the wall, thunderbolt optical cable goes | through the walls...) but the price and the failures | kinda scared me off. I get that this won't work for | normies, but personally I'd prefer to have the | transceivers and the fiber be separate so I can replace | one or the other if needed. Shipping it pre-assembled is | fine but given we're talking about a $500 investment here | I'd want it to not break in a year or at least to be | semi-repairable if it does. | Dylan16807 wrote: | > 3m is beyond the max cable length specified by | Thunderbolt, so it requires active extenders (they're | hidden in the plugs) and tight manufacturing and | shielding. You're paying extra for the ability to break | that max length spec, and it's one of only a handful of | products that do it. | | I'm pretty sure it's not breaking the spec. Are you sure | about that claim? | | And the main factor is almost always decibels of signal | loss rather than length, isn't it? | | > Also those Corning cables have a reputation for failing | barely out of warranty even if they are treated very | delicately. Amazon reviews are full of "my cable failed 1 | year and 1 month after purchase and Corning told me to go | eat a dick" type reviews. | | My understanding is that the thunderbolt 2 ones reliably | self-destruct but the thunderbolt 3 ones probably fixed | it? At the very least they can take a lot of physical | abuse. | | > 10gbps half-duplex USB 3.1 cable | | I don't think any of the high speed wires are ever half | duplex? | paulmd wrote: | > I'm pretty sure it's not breaking the spec. Are you | sure about that claim? | | Actually we're both wrong... it appears max length for a | passive cable is 18 inches for full performance. Passive | cables technically max out at 18 inches for 40gbps and | drop to 20gbps at 2 meters. Past that you need an active | cable (which has signal repeaters). | | Active cables generally run up to 2 meters (the Apple is | the first 3m active cable except for the Corning AOC | cables), but in most cases (everyone except apple) you | start dropping features like USB 3.1 or displayport. | AFAIK Apple's solutions are unique in that they don't - | like for example I looked up a 2 meter Belkin cable | advertised as TB3 and it doesn't carry the DisplayPort | channel. | | Which is why the advice for Thunderbolt is "just shut up | and pay apple their money". | | https://appleinsider.com/articles/17/08/15/psa- | thunderbolt-3... | | Not absolutely positive what the official standard is - | they might well only say the passive number (ie 18 | inches) because active can obviously be more or less | arbitrarily long with things like fiber, it might not | make sense to define a maximum cable length in that | context. Or they might amend it as they go... obviously | Apple has now broken the 2 meter barrier with their | active copper cable. | | I thiiiiink this becomes 0.8m for a passive cable in | USB4/TB4 as the official passive spec? CableMatters seems | to have a 2 meter active cable out though. | | > I don't think any of the high speed wires are ever half | duplex? | | High-speed is half-duplex, yeah. It looks like SuperSpeed | is full-duplex though so I'm wrong on that bit. | | I just remember it being a nightmare trying to use USB | external hard drives (which would have been back in the | USB 2.0/High-speed era when I used them last!) and | reading/writing at the same time tanked performance _far_ | beyond what you 'd get with even an internal HDD. Read or | write, one at a time, mixing both was a trip to hell. | | https://www.ramelectronics.net/USB-3.aspx | Dylan16807 wrote: | > Actually we're both wrong... it appears max length for | a passive cable is 18 inches for full performance. | Passive cables technically max out at 18 inches for | 40gbps and drop to 20gbps at 2 meters. Past that you need | an active cable (which has signal repeaters). | | I'm still pretty sure it's based on signal loss, and the | lengths are just estimates of what you can reliably get | out of a cost-optimized manufacturing process. | | > High-speed is half-duplex, yeah. It looks like | SuperSpeed is full-duplex though so I'm wrong on that | bit. | | By "the high speed wires" I mean the pairs introduced | with USB 3. Not USB's dumb naming conventions. | | > I just remember it being a nightmare trying to use USB | external hard drives (which would have been back in the | USB 2.0/High-speed era when I used them last!) and | reading/writing at the same time tanked performance far | beyond what you'd get with even an internal HDD. Read or | write, one at a time, mixing both was a trip to hell. | | I think a big part of that is also the mass storage | protocol combined with slow responses off a hard drive. I | have a USB 2.0 SSD-class drive around here and it | actually performs pretty well even on mixed workloads. | bombela wrote: | Can you use USB3 (whatever gen crap it is) for this | application maybe? | | I can drive an occulus quest2 via 8m of USB3 cable. The | cable contains a fiber optic with a repeater hidden | inside the female end. The total bandwidth this way is | enough for the occulus quest2 at 90fps. | paulmd wrote: | The goal here is wireless, a single thinner cable would | be better but it's better to not have to worry about | wires at all. And I'm not willing to set up a facebook | account just for a Quest. | | The Vive Wireless Adapter (VWA) is a PCIe card (single | slot/low profile/mitx length). The output from the card | is an SMA connector with a RF signal that goes to the | antenna, max official length is 2 meters (and it isn't | another SMA on the other end, it's hardwired into the | antenna, so you have to use an extension, meaning | multiple SMA connectors in the middle). I've seen people | use some fairly long extension cables, but that | attenuates the signal somewhat. It's _probably_ fine but | it 's undesirable. | | There are USB wireless adapters (TPLink makes one iirc) | but generally they are agreed to be an inferior solution | in various respects - higher CPU usage, higher latency, | worse signal quality, a green bar on the top, etc. This | is basically an ideal use-case for WiGig, it was | literally designed to be a wireless display transmitter, | and that's what the Vive Wireless Adapter uses inside, | it's actually an off-the-shelf Intel WiGig card. The | TPCast uses a much lower-bandwidth solution and | compresses it much harder and that requires more latency, | more oomph on the PC, and still gets a worse signal | quality. | | But, the WiGig card only has a short cable to the | antenna. Solution: put the card in an enclosure and mount | the enclosure on the wall, run the cables to the PC. | Problem: thunderbolt also only runs 2 meters. Solution: | optical thunderbolt cables. The rest is solvable from | there. | | The other reason I haven't raced into it is that HTC | hasn't kept it up with the newer hardware. The Vive Pro | has a higher-res screen and the VWA can only run at | (iirc) 3/4ths resolution. It's still a better screen, | there's less Screen Door Effect, but when you're talking | about dropping around $1000 to get wireless working | flawlessly and tucked away into the walls, it better be | fucking flawless. On paper the WiGig actually has three | channels and should be able to send on all three at once, | but this doesn't seem to be implemented... | | Honestly the TPCast is probably a 90% solution, it | probably chokes on the Vive Pro as well but maybe for | $200 instead of $1000 that's acceptable. But it's tough | for me to accept "good enough" when there's a technically | better solution. The VWA is an absolutely ideal solution | here. At one point there were some updates pushed that | looks like Valve was working on it, but (with apologies | to South Park)... in typical Valve fashion, "they just | sort of got high, and wandered off..." | | And then, the Index is just an all-around better | headset... but it doesn't have a wireless solution at all | right now (apart from maybe the TPCast?). It kinda sucks, | drives me up the wall that there's no "perfect answer" | here. Every solution has some large downsides. | jsjohnst wrote: | And? Apple used to sell a way more expensive than that | TB2 cable if high price is your point and besides, saying | Apple charges a premium price for a premium product (like | this) is about as insightful as saying the sky is blue. | CharlesW wrote: | FWIW, Monoprice's 1m USB4/TB4 cable (100W) is $25. | | https://www.monoprice.com/product?p_id=41946 | username190 wrote: | Apple's cable is 3m, which is likely most of why it's | more expensive. | | https://www.apple.com/shop/product/MWP02AM/A/thunderbolt- | 4-p... | jsjohnst wrote: | Their 1.8m cable is $129, so still >2x the price of | competitors. It's an extremely well made cable, but | overkill, probably? | [deleted] | a3w wrote: | USB 4 (opt) is ... optical? Or optional? | willis936 wrote: | It would have a longer max length if the data lanes were | optical. | johnwalkr wrote: | You can actually get optical usb3 and thunderbolt (all | generations) cables. Thunderbolt was originally called light | peak and shown off by Intel and Apple in demos as optical, | and Sony had a line of laptops with optical light peak | connectors to connect to external GPUs. But ultimately the | default became non-optical because it can carry power too. | mschuster91 wrote: | > But ultimately the default became non-optical because it | can carry power too. | | There's no problem in making a cable with two fibre leads | for data and two (at higher lengths thicker to reduce | issues with voltage drop) power lines. | johnwalkr wrote: | That's a good point although optical usb3 and | thunderbolt3 cables tend to be advertised with electrical | isolation as a feature and suggest using an external hub | to provide power.[1] | | [1] https://www.corning.com/optical-cables-by- | corning/worldwide/... | mschuster91 wrote: | Whoa, that pricing is quite a bit. | johnwalkr wrote: | Yeah that must be the real reason it didn't catch on as a | default. Light peak did have cheaper cables though, the | optical part was in the connector, not the cable. The | connector was a usb-a connector if I remember correctly.. | and the history is actually pretty interesting! | Apparently that connector was deemed proprietary and | frowned upon by the usb folks for causing consumer | confusion[1]. Kind of hilarious now, seeing how | thunderbolt 1/2 ended up barely being adopted outside of | Apple and usb itself is a confusing mess these days. | | [1] https://www.theverge.com/2011/10/14/2490694/how-sony- | acciden... | mschuster91 wrote: | > Kind of hilarious now, seeing how thunderbolt 1/2 ended | up barely being adopted outside of Apple | | Which is to a large degree the fault of Intel restricting | the TB spec to hell and back. | masklinn wrote: | According to the wiki table (https://en.wikipedia.org/wiki/USB4 | #Support_of_data_transfer_...), it's "optional": | | * "USB4 20 Gbit/s Transport" (= USB4 20Gbps = USB4 Gen 2x2) is | required for host to support | | * "USB4 40 Gbit/s Transport" (= USB4 40Gbps = USB4 Gen 3x2) is | not | | Also USB4 apparently only requires support for tunneling | "SuperSpeed USB 10Gbps" (USB 3.2 Gen 2x1), "SuperSpeed USB | 20Gbps" (USB 3.2 Gen 2x2) is optional. | kashunstva wrote: | > May 05, 2025 | | The article is dated May 5, 2025. I've long been wondering about | the future of USB. | Beta-7 wrote: | USB 4.2 (later renamed to USB 3.2 gen 2 Mk. 1) comes with built | in time traveling. They just keep adding features to the | protocol and making it complicated. | notorandit wrote: | Not to be read before: see article time stamp | vesinisa wrote: | OP forgot [2025] from the title. | WithinReason wrote: | I could still fix it, but I fear the wrath of Dang | Fatnino wrote: | It's a form of SEO. Google promotes "fresh" content, so if it | sees a date less than a year ago it often assumes the content | is better. Normally you will see this abused by crappy content | mills using a plugin that constantly updates the date on their | garbage. | | Putting a static date from 3 years in the future seems like a | quick a dirty hack to do the same thing. | IshKebab wrote: | This is wrong. For example Full Speed isn't a name for USB 1, | it's the name for a speed which is supported by USB 1 _and_ 2 | (not sure about 3). Most USB microcontrollers are Full Speed USB | 2. | gsich wrote: | CC1 and CC2 pins are missing. | megous wrote: | They are not required to be wired through all cables. Similar | to SBU signals. | Tepix wrote: | I have a related question: | | Is the official name | | USB 3.2 Gen 2x2 | | or | | USB 3.2 Gen 2x2 | | (x vs x)? | jjoonathan wrote: | Which USB do I choose for a 4x4 offroad adventure? | masklinn wrote: | The USB pages and specs (on usb.org) seem to use "x" where they | use the technical spelling. ___________________________________________________________________ (page generated 2022-05-05 23:00 UTC)