How does a USB keyboard work? 

USB can push, but to my knowledge not for peripherals. Audio devices for example, can ask the host to push data IIRC. The complexity mostly due to the need of supporting a bunch of devices. These device have their own needs and data protocols. USB separates this as classes.

Actually, that's sane, which is the opposite of insane.

I think USB3 is capable of pushing Edit: USB 2 is capable of that too, it just takes the right keyboard/mouse that supports it

@@UltimateAlgorithm but what about the num lock, caps lock, and scroll lock lights?

I know But There’s ☝️ Scope That Beats All And That’s Your First ☝️ I’m Still Waiting For GOD To Bless Me With ☝️ Until Then I Continue To Pray Someone Throws An Old One Out Because They Upgraded.

I'm a electronic engineer student. I confirm, yes. The most simple thing, like, 'Oh this thing only switch on and off the light' yeah, no. Maybe this cost hundred of hours in research

If you go the magic route, you can actually get quite a bit deeper. Q: How does that thing work? A: It's magic. You see, those things are filled with rocks, and those rocks have microscopic glyphs written upon them. Those glyphs interact with each other in complex ways to produce the effects you see.

Technology is magical artifacts designed by wizards we call scientists.

Its disappointing to see everybody takes these hard earned technology as granted

@@johncochran8497 Paraphrasing a popular tweet from ages past: A computer is basically just a rock that we trapped lightning inside and tricked into thinking.

I love this approach! I do a similar thing when I run into cryptic programming algorithms that I don't understand: pull out a notebook, and go through the code line by line until something clicks. It can be very tedious, but when I'm working with something I find especially opaque, it takes away all the abstraction and make things feel more "real". The same sort of thing could be done by running the code through a debugger and watching a bunch of expressions... but there's something about manually writing things out on paper that makes information register better for me.

Yeah, Ben is the best teacher of this stuff that I've ever seen. He can explain anything in a way that just clicks with me.

The USB specification is one of the most readable technical documents I've ever seen. That will have helped, somewhat.

@@MixMastaCopyCat Booth's Algorithm to multiply negative numbers I used this approach !

I do this in my day job. Some times you just have to think it through like this...

Bens uncertainty therory. A datasheet when observed, can either have a lot of precision but lacks in clarity or lacks in precision with a high level of clarity.

This video's got a lot of precision but also a ton of clarity.

That really is how a lot of specs are

@@markoap91 but that makes it 34 minuets long. So there is always a tradeoff

@@sayamqazi I know it can be hard to find the time to watch something like this. But if I have the time these kind of videos glue me to the screen and 34 minutes passes like 34 seconds. Plus, there are tons of watered down videos out there that explain things in simple terms so that you get the idea, there are not enough videos that go into this much detail to really SHOW you how something works and demystify it completly.

That’s pretty much what engineering becomes at this level of complexity… you convincing yourself that things seem correct based on logic rather than always being 100% sure of everything. It’s often impractical to know things absolutely.

@@ShALLaX It's just nice to know that even when you're ben eater you can't be 100% sure of everything

Strange

Uh oh nope

Ah yes, that great feeling that your theory or comprehension of theory seems to be right and mirrors in your test results :)

don't keep the knowledge to yourself like a hoarder, make a video! I'll watch!

pls share resources 👍

Currently doing exactly that to create a driver for an old scanner that isn't properly supported on Linux. I'm using Wireshark on Windows to figure out the communication protocol and then reimplement it under Linux. Such a pain in the ass. USB is so fucking complicated.

Yes, especially if you also enable to the USB PCap which is a Wireshark installation option on the later versions. Worth scoping out, for sure!

it sucks with windows unfortunately, works fine with linux, not sure about macos

The only thing I can possibly think of that could beat the visceral qualities of writing shit down on paper is MAYBE just doing that but in AR glasses.

@@williampasbrig3677 Yeah i like that he is writing it on paper too!

yeah. also, never heard of actual data export in csv format or similar? Which can then be properly plotted on a computer? Dude seriously, cropping screenshots together in freakin PS? Okay then.. BUT: Awesome video and explanation!

@@RandomUser2401tbh combining screenshots is probably easier than taking a csv export and plotting it in excel or something. You could combine that screenshot in mspaint in like a couple minutes or probably less

@@misaalanshori if you don't plot for the first time, plotting a csv is a matter of minutes. Exporting all the different png screenshot takes longer than that. Hint: Serious plotting is not done in Excel, but python, Matlab, Octave etc

lol, he's also good at explaining.

*Computer architecture/electronic engineering

This was a happy little journey into the USB protocol!

Perfect.

Ahahaaa very well said!

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-kOkV9BalNcw.html

Factorio uses a lot of cords, and some ghost on cheaper keyboards.

My Logitech Lightboard XL only supports 2 keys at a time which makes it impossible to perform speedrun jumps eg. Amazing how this silly looking keyboard can handle up to 6 keys!

For PhD's it's not really surprising they don't excel at teaching, since they focus on research and academia, which unfortunately does not reward teaching skills at all.

$7,000? Thanks for saving me a search and crushing my dreams in one comment ;)

And to think you can spend a measly $200 (student price) for a Discovery 2 and a Sigroc free download and do almost the same thing. And it does dozens of protocols.

@@katemoon7476 BeagleBone Black running BeagleLogic + sigrok would be even cheaper, but it's only a logic analyzer (100 Msps 12 channels) for 2.5V-3.3V digital signal (unprotected 3.3V digital inputs) unless you add an external level shifter, and user-friendliness is probably sub-optimal (though I haven't played with it myself yet). Though on the plus side, whenever you have no need for logic analyzer it's still a beaglebone you can use for other things.

@@katemoon7476 DSLogic Plus $100 (cheaper if you are willing to make RAM mod), 400Mhz and software is actually usable.

To be fair it probably cost them like $50 to produce.

Can we appreciate the fact that this is probably the first and the last "next video" comment that might be true.

@@techleontius9161 Yea, i just thought of using a Arduino instead to convert USB Keyboard to PS/2 Scancode

Yes. Maybe an Arduino Mini can be used here for reduce complexity. I use Arduino Micro for creating USB SNES and NES interfaces to PC or PS3. It's a real help to use it.

I used a ftdi ft313h to use usb on my 65c816/6502 build because the massive overhead of trying to process usb packets.

Would it even be fast enough to handle USB? I think it'd need to go into some type of buffer.

Usb is the lethal weapon?

funny you say low level computing- to the average person even the display of an oscilloscope looks like magic.

Low level dosenot mean esay. It means near to hardware level.

What is the company you found?

Your company name?

I agree

Hope to see usb 3 sometime

There is no protocol that is more complicated than USB

up next, bluetooth

@@rasz I would also be interested in this, we didn't really talk about it in depth in my computer networks class at my school

How is the latency on Bluetooth? Probably more than 1ms

@@vadzimdambrouski5211 At best, it can be as fast as 800Hz (1.25ms) but this is not typical. Bluetooth, at least Classic Bluetooth, had 1600 slots per second where the master polls each device in the piconet and each device responds. If there is only 1 active BT device in the piconet and if the packets are short enough to fit in 1 slot, then the polling can go as fast as 800Hz since the master and slave will alternate slots. However, most Bluetooth mice and keyboards use Sniff Mode to schedule how often to be polled (vaguely how the bInterval value affects USB's Interrupt pipe polling rate). On the upside, the Sniff Mode polling rate can dynamically change during a connection. For example, a mouse may ask for a very fast polling in Sniff Mode while it is moving. After a few seconds of no movement, it may ask for a slower polling rate (save power, allow more traffic for other devices). After a minute of no movement, the mouse may ask for an even slower polling rate. After several minutes of no movement, it may even disconnect from the Bluetooth piconet and go to sleep. If moved, the mouse will reconnect and go back to the fastest polling rate.

@@ChrisDreher if BT can reach 800Hz, why almost no device use them? BT peripherals always feel slow compared to USB cable, or even dedicated wireless. This is especially apparent when using high refresh rate display. On these display, it is easy to tell between BT or USB (wired/dedicated wireless).

@@UltimateAlgorithm This is partially answered above but it mostly comes down to 2 main factors. First, Bluetooth is a bus that Bluetooth devices share. The more devices you connect over Bluetooth, the less bandwidth that is available per each individual device. This is why some dedicated/proprietary wireless mice can be faster (depends on the wireless technology). Second, just like the difference shown for USB in the video, how responsive a mouse can be depends on how the manufacturer tuned the mouse's Sniff Mode polling rate. For example, Bluetooth gamer mouse will have a faster polling for better responsiveness than a business mouse or low-end mouse that will have a slower polling rate to extend the battery life. Third, and not mentioned above, is that USB has much more bandwidth than Bluetooth. So while USB has frames at 1000Hz, which is slightly better than 800Hz for Bluetooth (a best case), USB bandwidth allows for multiple devices to communicate in a single frame but Bluetooth can only have 1 device communicate in a single slot. This tends to push mice manufacturers to use a slower polling rate over Bluetooth so that other Bluetooth devices don't get starved for bandwidth. Part of the reason for "one device per slot" is that encryption and wirelessness is complex, difficult, and inherently noisy (problems that USB doesn't need to deal with as much).

@@ChrisDreher that make sense, shame that most gaming devices opt for proprietary connection instead. No one is actually making fast Bluetooth peripherals. Maybe it's bad marketing in game industry, where Bluetooth keyboard and mice synonymous with high latency. Although this doesn't happen with gamepads (PS, Xbox and Switch). All use Bluetooth yet have very low latency, on par with proprietary keyboard and mice.

God I hope not. This is pretty basic stuff.

@@stargazer7644 maybe, but school doesnt teach this way. They would spend weeks doing what he fit into a 30 minute video.

@@mrlithium69 Or leave it as homework for the student and move on to the next topic.

@@stargazer7644 just curious what your job is if this is simple?

@@TheFool2cool Electronics and software is my hobby. I design and build PC boards for fun. Protocol reverse engineering and troubleshooting is a common part of electronic design. When you're trying to get your microcontroller talking to some other piece of hardware, this is what you have to do. I studied electronics in school, but my day job is in Information Technology.

like for that 😂 face

This “thing”? You mean this channel?

He probably means he already knew everything that was taught before, but now things start to be interesting in a new way

Did you comment before you realized it wasn’t a breadboard computer episode?

It is radically changing the world

It's not smart, it's just stupid faster

@@asedtf I'm saving that quote, there must be some situation I can use it in

I mean sure, it's two wires of regular old copper, it's not like USB introduced new physics

In those 40 years, we went from serial for everything, to parallel when bandwidth was required (Laplink went so much better over parallel), and then with USB, back to serial for everything, only without giving up the speed. Then USB 3 sends us back to parallel (what do you think those extra 4 lines are for?). Time really is a flat circle.

Same thing with DSL: no different from 40+ years ago transmitting data over 2 wires of copper, just with advanced modulation techniques for much higher data rates.

now i wanna see how USB data transfer works, as opposed to HID in this video and also... IMPLEMENTING NTFS FILE SYSTEM ON 6502 when?

It's so universal!

@@Kitulous USB data transfer would be cool to see, as well as USB audio interfaces. Real time audio is one of the most complex things you can do over USB.

Technically nes used 6502 and people actually managed to run doom on it lol

We can only hope!

@@xugro no, they didn't. The "Doom on NES" runs on Raspberry Pi that's stuffed inside the NES cartridge, it runs doom and then inserts the image of the game in real time to the APU graphics memory... so it's not truly running on the 6502...

@@Mtaalas Thats.... a bit disappointing :(

the BBC Micro is able to run a 3D wireframe based game (Elite) pretty decently while running at only 2MHz, Ben Eater can easily upgrade the Computer to run at 10MHz (by simply using the same clock for the CPU and VGA Circuit) so it could probably run a simplified version of the DOOM Engine... and with "simplified" i mean that to run at playable speeds you would likely need to lower the overall resolution and color depth to minimize the amount of data to be moved around or maybe just aim for Wolfenstein 3D since that's only raycasting with some 2D Sprites thrown in the mix which is much easier to do than a complete 3D renderer

ahahaha

the switch is such a cheapo device lol

So just use third party usb c to hdmi converter

Lol what, how did that get through the EMI comformity tests? Did they do it in-house? Independent labs usually catch those issues with no problem!

you mean shielded. Not insulated.

Wow you people really call those electrics classes. Must be electronics. Michi.

Cool Michelle, we can do friends ??. I love that subject mechatronics or animatronics.

@@matata3D2s yall thirsty af 💀

As far as i understand, is that PS/2 has a hardware interrupt in a proccessor, where a USB device has to wait untill it gets pulled and handled by software/processor. (but im not 100% sure)

@@marcoboot18 Did you even watch the video? lol

@@TheNini666 the video does not really address what he said. USB keyboard can't tell independently if something changes. It can only answer when the host (computer) asks "what's up?". In USB host needs (AFAIK) keep generating those "what's up" requests, which is away from executing application code. PS/2 keyboard uses HW interrupt to tell the host when it has something to say. I guess this does not really matter anymore. Maybe it did 20 years ago.

@@fl4shi238 I'm fairly sure the polling is taken care of in hardware by the USB host controller, which then uses an interrupt to notify the CPU of data when something is actually received and not just NAK'd. So the CPU really doesn't have to bother with the low level polling. There are many different host controller implementations though, so some may be different.

@@TheNini666 Marco is absolutely right. USB devices are polled by the USB host.

If you generalize it to "a lot of things happen very quickly" it's broadly applicable to almost every question involving computers.

lol you could litteraly write a 1000 page book answering that question

@@ashen_dawn Stealing this

And they wonder why computer scientists love layers of abstraction. At the highest level of abstraction...yes stuff happens and it works.

They're just specialized computers, the highest end ones have surprisingly powerful GPUs just to try to emulate the ancient boob tube better...

@@NiHaoMike64 I'm from this millennia and so it took me 2 seconds to figure out what'd you meant by boob tube xD

Logic analyzers with a sketchy DSO onboard

@@NiHaoMike64 What is a boob tube? The only definition i found is TV, but it makes no sense to me...

@@Gigasimo456 Slang for CRT, what was used to make oscilloscopes before high performance ADCs became affordable.

Don't lie

@@sookmaideek I don't always troll but when I do, I troll hard... No wait xD

Surely lots of those pages are standards for the physical hardware and can therefore be ignored?

@@xTheUnderscorex oh, no no no, we need FULL standard, complete with USB-C support

@@PsychoBelka lmao, lemme guess - you want USB3.1 thunderbolt support on the breadboard ?

@@cezarcatalin1406 dont you want it?

@@PsychoBelka implementing that is a hell of a ride xD. I put a USB-C on one of my PCBs and hooking up the Controller chip with all its data and power pins to the chip and the battery was already slightly more complicated than I thought, imagine going from zero to that.

My laptop's touchscreen uses a USB interface and appears as 2 devices when I listed the inputs and I never knew why, I thought it could be some Linux driver shenanigans. Maybe this have some relation. Very interesting

Is that how they get the "N-key rollover"?

@@Luiz6247 Linux ecosystem generally does not tend to go for shenanigans at least inside core components and system utilities. They just show all the ugly truths and dirty hacks as they are.

Gold I can't imagine what part of the USB association convoluted licensing platform this would be a loophole of.

@Manypeopletrytosee99 firstly, that's a function of hardware support, not base design. Second, Linux has gotten better with driver support since when you probably last heard about it in 2006. There are more free drivers in Linux, and also more blobbed drivers, though the latter isn't good.

any books/documentation /learning path that you'd recommend?

@@LuckyST probably not. he full of horse.....

@@randokaratajev2617 how bout you then?

You sir are cool

@@LuckyST Depends on what you're trying to achieve. If you're looking to get a general understanding, there's a PDF called USB in a Nutshell. If your goal is understanding the protocol enough to be able to build your own USB hardware. Jan Axelson wrote some very cool books. There are books from other authors, but they all boil down to the official USB specification. Get the 2.0, not earlier, not the 3.x either, I’d explain later. A couple of class specifications and tables with all the necessary values will be needed further down the track. It’s also recommended that you get the most familiar starter kit that you can find with a real USB core inside. FS (full speed) is good enough, HS would be an overkill and complicates things. Without picturing how you plan on altering the code for additional fancy features, try to run a few basic USB demo projects and get the kit running as intended, it should help you straighten up the dev environment and get you warmed up. Then comes the hardest part, intensive reading, you probably need hard copies of the most frequently referenced materials because all your fingers will come in handy as bookmarks to grab hold of / insert between the physical pages. Get the most comfortable mind map utility you have. I used a lot of blank sheets of paper back then, if you work more with digitized alternatives then that’d be better. You will run into a ton of terms and abbreviations that are both strange and related with each other. Before connecting the dots, you need to put them down somewhere like pins on a map. All the words read like nonsense to me in the beginning, it took me a lot of jumping around different paragraphs across different books before the Eureka moment dawned on me. And then I knew why the demo project was structured in a way to have all the strange structures organized in a handful of header files. All the descriptors and reports were just closely grouped there so it’s easy to customize them for new features. If you’re looking to understand USB on a deeper level and tweak around the signaling, probably working on FPGA cores in the future, the aforementioned route should familiarize you with the application layer. I never looked this deep TBH, but there are two places to look into if you’re determined. The USB core library of the starter kit, and some low speed keyboard / mouse projects using general purpose IO pins as D+ & D- signals to build the protocol from scratch. Existing projects are mostly the work of gurus and they are well structured for the sake of better maintainability or whatnot, which adds to the complexity to understand them. If I had the time, I would’ve built the code from the ground up, trying to experience every step it took the guru to figure out how each tiny bit of detail adds up. Making a bunch of ugly code work would’ve been my first milestone, finding ways to optimize them into something close to the existing demos would be the next. By then, I would have really understood why everything is the way it is. And I’d be able to advance into the FS signaling, later HS. Gen 3 and Gen 4 won’t be like total gibberish any more.

depends on what the latency is between press and being ready to send the packet between keyboards

I feel like he'll eventually come to that

This makes me think the issue some feel with USB (Not me) might not be the latency itself but it’s variance. Instead of the predictable and repeatable latency of interrupt driven PS/2 they get subtle variations. In other words USB introduces jitter. I don’t know if a trained human can detect such minute differences, especially with all the other latencies involved in the modern gaming feedback loop.

@@rdoursenaud I'd be curious to see someone make an honest scientific (independent, randomized, double blind, ...) attempt to measure a performance difference that mattered in actual use. With old cheap USB keyboards in the early days of USB (possibly with bugs and just without any improvements a modern gaming keyboard would have)? Plausible that you could measure a real world difference, though I'm not sure a typical gamer would show it. Might require an elite level player to matter. But with a modern high quality well implemented gaming keyboard vs. a high quality PS/2? I'd be curious to see the experiment which would measure the practical difference. I could easily believe that there are badly implemented gaming keyboards out there, though. And I could believe that thinking you had a better keyboard might have a psychological difference regardless of which you thought was better and which one you actually had. Double blinding would be important. But ultimately it seems unlikely to me that you could measure differences that small. I'd expect them to be in the noise.

@@ratchet1freak Indeed there will almost certainly be at least some delay even for the PS/2 keyboard as I would imagine they probably implement some debouncing too. Human movement is pretty jittery at the micro scales which can be a problem right at the threshold of making or breaking the circuit. Adding a short delay before reporting the event helps prevent spurious input especially with the sort of soft switches you get in keyboards where there is no mechanical mechanism to ensure a hard transition from one state to the other.

That's really cool and nice sona btw :3

See the signal... I wonder if Geordi La Forge's visor connects over USB? Then again I suppose he can just signal for data any time

type-c for the win!

@@victortitov1740 Today, it took me two attempts to plug in a type c cable. There are still ways to get it wrong if you really want.

@@darranrowe174 im dying 😂

That's because USB-A is 4 dimensional: it doesn't fit on the first try, when you turn it around it still doesn't fit, but on the next turn around it finally works ;)

That sounds like a very good way to advertise the Keysight product, since it would be immensely useful for USB hardware debugging...

I think decoding USB is software part

@@Gameplayer55055 Probably the most of added cost is for the software upgrade.

@@lifthras11r you can get a logic analyzer for much cheaper, since it isn't concerned with actually looking at the shape of the waveform, only the level changes! Then you can pull the data into software on the computer that decodes the data for you. It's neat!

@@lifthras11r ye

Very similar here. I took a dive into the spec but god is it lengthy.

Yup, same, I'm going to do a simple keyboard with raspberry pico and this video came in a really good timing

@@tomiesz usb is supposed to be universal *and* plug and play, so naturally the spec will be absurdly large. very similar story for bluetooth

the amount of use cases is directionally proportional to the size of the spec

@@tomiesz for just 2 data lines, it sure is!

Nerd (Not a bad thing, Nerd = Smart And interested in learning)

General-purpose keyboards usually have their matrix lanes built in a way that prevents ghosting when typing, at least in English. Cheaper gaming keyboards usually have different matrix lane layouts that prevent ghosting when holding down keys that are frequently used in gaming, such as WASD QE and the space bar. Higher end keyboards use diodes, higher lane count matrices, or individually addressed keys (for example fully-configurable RGB keyboards), and they either negotiate longer data packets, faster polling rates, or report themselves as multiple keyboards.

With USB-C it's always plugged in correctly the first (and every) time😁

yeah they really took all the fun out of it

I believe USB-C does still have a D+ and D- that could be setup to be different, but it would have to be designed intentionally to be obtuse like that. So unless your EE is a troll, it's is for all intents and purposes symmetrical.

@@skaphanatic5657 Symmetry is required in the standard. If your EE makes it asymmetrical, then it's not USB-C.

@@coder0xff But there are crappy chineese USB-C to USB 2.0 adapters on the market that break the standard by only connecting D+/- wires to one of the 2 pairs. On some PCs they only work in 1 position and there is no way to know in which one until you try them and put some marking on the adapters yourself.

Yes, you can see this immediately when he lays out the printed copy at 5:24 or so. It's much easier to see on the D- line than D+, because D- is high when the keyboard takes over driving the line. This can actually be a lifesaver when debugging any multi-drop bus because it's so easy to get confused about who is driving at any given moment. In fact, a very useful debugging hack is to put a small value resistor either in series with the data line at one device or in series with that device's Vdd line (emphasis on the words "small" and "hack"). The idea is to lower the driver's Voh just enough to make the difference visible without compromising the data.

I don't think the CPU is handling the polling. I believe the UBS interface chip handles all of that and then generates an interrupt for the CPU when necessary.

Wouldn't pulling the key presses be the job of the operating system?

@@xugro depends on the USB controller they have, which is a microprocessor in itself and could do the polling on each connected device and then generate an interrupt to the cpu on a new input packet. At that point the real limitation is the polling rate.

@@xugro What Nicholas is saying is there's a dedicated chip that polls and buffers keypresses and raising an interrupt on the CPU just like a PS/2 would. But i find that unlikely myself. Possible for sure but not likely. The OS has USB drivers and handles all that. If the kernel is hung up then something horrible has happened, something you aren't likely to fix with a keyboard.

I know that things are more complicated under the hood, that's why I said I don't know if this argument is 100% factually true. I know the USB is managed by a chip (a quite capable one these days), but I do not know in what conditions it generates interrupts to the processor. Plus, I think the first USB chips were not that smart and not sure if they could understand that they are talking to a HID device, that must pull every so often. I hope someone with more insight will show up to clarify some of this.

they have a lot of fpga magic inside. the higher the frequency and accuracy, the insanely expensive they get.

@@stefanweilhartner4415 what is the price of that thing?

Its more of a logic analyzer, than an oscilloscope. Amazing piece of kit.

fun fact: the manufacturer of the one on this video (Keysight Technologies) was originally HP.

@@mel816 Who also bought out Agilent! At work still have some HP and Agilent equipment sitting in old test racks.

1am? It's 5am in here bro