ericbarrettNov 2024Strongly recommends
Among other things, the USB host polls the keyboard at a fixed rate. Fantastic breakdown if you have 30 minutes: ▶ this video
in “Only buy a magnetic keyboard for gaming” · View on HN
How does a USB keyboard work?
How does a USB keyboard work? on HackerTube: recommended by 7 Hacker News commenters across 6 separate months, 2021–2025.
Ben Eater
Open on YouTubetutorial · intermediate · evergreen
Ben Eater explains how a USB keyboard communicates, covering the electrical interface, bit and packet encoding, packet contents, and a comparison with PS/2.
Why Hacker News recommends it
HN commenters recommend it as a clear, comprehensive explanation of USB signaling and keyboard polling.
- people recommended it
- 7
- separate months
- 6
- strong recommendations
- 2
- discussed on HN
- 2021–2025
“Fantastic breakdown if you have 30 minutes”
What HN commenters said
12 Hacker News comments link this video. Each one links back to its thread.
jordibcMar 2022Strongly recommends
About the USB keyboard, that may be true only for the cheapest keyboard you could find, but basically not applicable anymore nowadays. Rather than giving you the details, let me link to this video, which is awesome at explaining it and much more -- the USB vs PS/2 part starts here: ▶ this video
in “The end of the nice GTK button” · View on HN
lozengeSep 2022Recommends
Ben Eater has some videos showing the USB protocol on an oscilloscope. ▶ this video [link] And some videos on using chips and breadboards to meet protocols- [link] And a digital protocol too- [link]
in “Ask HN: How do I write a Linux driver for my 15 year old photo printer?” · View on HN
jai_Jun 2022Recommends
If you're interested, here's a really comprehensive video on how USB keyboards work which may answer your question: ▶ this video
in “How to Make Rust Leak Memory (Also: How to Make It Stop)” · View on HN
throw0101aNov 2021Recommends
> Embedded programming? Dealing with signals?! God forbid, man. "How does a USB keyboard work? by Ben Eater: * ▶ this video
in “What is AT&T doing at 1111340002?” · View on HN
wmwmwmSep 2021Recommends
There’s a great video here that goes through all this - the gist is that USB keyboards specify what polling rate to use, 1000hz for the best ones, maybe 125hz for the cheaper ones. An interesting thing about ps/2 is that even though it doesn’t have to wait for the keyboard to poll it transmits data at much slower speed than USB (khz vs mhz) which somewhat offsets the advantage it gets from being interrupt driven ▶ this video edit: ah, sorry, I see someone's posted a link to this video already!
in “Keyboard Latency (2017)” · View on HN
Show 6 more comments
exporectomySep 2021Recommends
Apparently [1] PS/2 limited by a slower data rate than USB 2.0 which cancels out almost all the advantage of its lower initial latency to begin the transmission, making them both about equally capable in actual latency - at least in theory. [1] ▶ this video Even if this conclusion is wrong, that video is a very pleasant and understandable explanation of the USB protocol.
in “Keyboard Latency (2017)” · View on HN
jeroenhdJun 2025Cites it
Serial ports still exist today. Even in desktop computers (though usually in weird underpowered ones designed for industrial applications and such). Even the most GAMING of motherboards have headers ready for one or even more serial ports to mess with. All you need is a cable and a card to slot into a PCIe bracket! USB itself, at least the 1.1 protocol that's still used for some devices today, isn't all that complicated in itself: ▶ this video Many if the complicated parts here, like device identifiers, are the things you'd need to manually configure if you were to use a serial port. Those hundreds of pages are similar to the hundreds of device types, vendors, and models that Windows would list when you clicked "add new hardware" back in Windows 98. When push comes to shove, you're just sending energy pulses down wires, there's just a chip in there that helps collect pulses so you don't need to manage the timing manually.
in “Writing a basic Linux device driver when you know nothing about Linux drivers” · View on HN
lasr_velocirptrMay 2023Cites it
PS/2 Keyboards are faster than a USB keyboard with slow-speed negotiation with the host computer but for USB keyboards with high speed negotiation, they are at par[1] [1] ▶ this video
in “Measured typing latency of popular terminal emulators” · View on HN
em3rgent0rdrApr 2022Cites it
I'm sorry but serious question, why would you need a high-speed for a keyboard? A usb packet for a keystroke is roughly 180 bits (I'm estimating from glancing at ▶ this video ). So 1.5 Mbit/s low speed could roughtly handle over 8,000 keystrokes per second. Do you really need more keystrokes or finer resolution than that?
in “A blue connector does not USB 3.0 make” · View on HN
RJIb8RBYxzAMX9uOct 2021Cites it
I'd imagine it would be very difficult, and would require a relatively powerful MCU. Ben Eater's made a few videos discussing how PS/2[0] and USB keyboards[1] work. USB's a vastly more complicated protocol compared to PS/2. [0] [link] [1] ▶ this video
in “IBM PS/2 Keyboard Modification” · View on HN
thristianJul 2021Cites it
Piggy-backing this comment to add some context for the OP video: This "USB device discovery" video is actually the latest in a series of videos where Ben Eater is building a simple 8-bit computer on breadboards. He hooked up a PS/2 keyboard as an input device, and then got sucked into a tangent of investigating and explaining keyboard protocols. - He investigates the PS/2 keyboard protocol: [link] - Somebody on Patreon asked about USB keyboards having higher latency than PS/2, so he made a video about the basic USB protocol: ▶ this video - He made the OP video about USB keyboards being limited to holding six keys at once.
in “How does USB device discovery work? [video]” · View on HN
Topics & tags
Electronics & circuit designEmbedded systems & DIY electronicsComputer architecture & CPUsusbkeyboardsps/2pollingben eaterhardware