[HN Gopher] How I built a keyboard/video/mouse switch for my two...
___________________________________________________________________
How I built a keyboard/video/mouse switch for my two 4k monitors
Author : car
Score : 165 points
Date : 2020-09-02 19:56 UTC (3 hours ago)
(HTM) web link (haim.dev)
(TXT) w3m dump (haim.dev)
| yfiapo wrote:
| That's cool. As another alternative, this is the one I bought at
| start of lockdown which does everything but the USB-C:
| https://smile.amazon.com/gp/product/B0851CMHP2/
|
| Not particularly cheap but at least no longer back-ordered. I've
| been pretty happy with it switching 2x4K monitors, keyboard and
| mouse between a Mac and a PC laptop. Both corporate laptops where
| custom software is more difficult.
| dkersten wrote:
| Hah, I use a low tech solution: I have a HDMI extension cable
| that reaches the front of the monitor that I just plug the device
| I want active into (and a usb splitter similar to what he uses
| for keyboard and mouse). It's not quite as seamless as the
| solution described here but it took no time to set up.
| evanweaver wrote:
| You can get a physical HDMI button so you don't even have to
| unplug anything: https://www.amazon.com/gp/product/B01L8LLP2G/
| pstrateman wrote:
| "4Kx2K@30hz resolution"
|
| The issue is 4k@60.
| dkersten wrote:
| Yeah, I did use a switcher before I upgraded my resolution.
| Yetanfou wrote:
| I have another solution to the same problem using a monitor
| which has both HDMI and DVI. The HDMI port is used for the
| 'main' machine which the DVI is connected through a DVI-HDMI
| connector to any secondary machine which I may want to connect.
| Switching between the two is either automatic - when there is
| no signal on the DVI input - or through the monitor source
| selector. The monitor also has a few analog inputs which I have
| used on occasion with older laptops, extending the scheme even
| further. Of course this only switches the monitor, not the
| keyboard so it is not a complete replacement for a KVM switch.
| hinkley wrote:
| If you get some short extension cables, then most of the wear
| will be on the cable instead of your devices.
| dkersten wrote:
| That's basically what I have: extension cable from monitor to
| front of monitor and HDMI cable from device to extension
| cable. So worst case is I have to replace either the
| extension cable or the HDMI cable. Either way, no biggy. I
| guess I wasn't clear that when I said "I plug my devices in",
| I meant a HDMI cable that then stretches to the actual
| devices, so they don't need to be at the monitor (eg my PS4).
| nkrisc wrote:
| This is perfect. The software competent is exactly what I was
| missing from my setup. I use a USB switch to switch my
| peripherals but I've been manually changing the input on my
| monitor like a caveman.
| joshu wrote:
| I use the IOGear switch between windows/pc and like 1/5 times it
| doesn't switch correctly (it'll end up holding the option key
| down or something.)
|
| are there any keyboard switches that emulate a keyboard correctly
| instead of just unplugging and replugging the usb connection?
| duskwuff wrote:
| > are there any keyboard switches that emulate a keyboard
| correctly instead of just unplugging and replugging the usb
| connection?
|
| StarTech's KVMs have a rather robust USB stack which handles
| this situation very well.
| joshu wrote:
| thank you! any particular products you have experience with?
| zerkten wrote:
| I've given up finding a KVM that has this support for
| emulation. I've got a Kinesis Freestyle Edge RGB and even for
| the better ConnectPRO KVMs, there are just too many USB
| endpoints.
|
| I found that X-Keys make a range of keypads that are
| specifically designed for KVMs. I have it setup for KVM
| switching and the remaining keys have other macros. I'm glad I
| got it, but it's expensive compared to DIY kits.
| AntiRush wrote:
| This is awesome!
|
| I've often dreamed about doing this with a keyboard shortcut ala
| switching layouts in a tiling WM (or 'real' kvm switches from the
| CRT + ps2 era).
|
| Is there a good usb hub that supports switching outputs via
| software?
| bertjk wrote:
| Some of the IOGear KVMs do provide hotkey functionality.
| TehCorwiz wrote:
| This would probably work great for running VMs with a hardware
| pass-through GPU. Can't wait to try this out.
| aloer wrote:
| I recently bought a Philips 346b1c (34" UWQHD with built-in USB C
| hub + KVM) and the use of DDC/CI to tell the monitor what input
| to switch to could come in super handy here.
|
| The display is very good at automatically switching KVM based on
| the selected input, but the selection still has to be done with
| the little buttons underneath the screen
| dasloop wrote:
| I have an MX Keys keyboard that can connect to up to three
| devices (with three special keys). Unfortunately, the operating
| system does not see the key pressed. But if it was, I could
| activate the display input switching using your app (thanks!). I
| have filled a support request at Logitech, maybe one day...
| OJFord wrote:
| Are other keys (e.g. Fn) mappable to the special keys? Maybe
| you could work around it by setting e.g. F1-3 to F1-3 +
| Special1-3, and then input switching on F1-3.
| [deleted]
| dugmartin wrote:
| I use a combination of a cheap USB switch and the remote for my
| 4K monitor (really a 43" TV) to switch inputs. Not as nice as one
| button press but much cheaper than a high end KVM.
| NKosmatos wrote:
| Reminds me of a similar post in HN in order to switch inputs on a
| single monitor, between mac and PC, via software only. Ideally a
| shortcut on the mac desktop in order to switch to HDMI and
| another shortcut on the PC desktop to switch to DisplayPort. For
| sure I'm going to give a go at the code of this soft/hard KVM.
| doctorhandshake wrote:
| There was a comment here yesterday[1] about DDC/CI writes being
| finite on some hardware -- is that a concern with this approach?
|
| [1] top comment - https://news.ycombinator.com/item?id=24344045
| justaguy88 wrote:
| for those who have less time than money,
| https://store.level1techs.com/?category=Hardware
| D13Fd wrote:
| Both of the KVMs meeting his criteria on that page are sold out
| (and one is a pre-order as well as being sold out).
| vaillancourtmax wrote:
| Neat!
|
| I use a similar setup where I literally have a single USB cable
| that gives me access to everything: monitor, keyboard, mouse,
| lighting, camera, microphone.
|
| I just need to plug the cable in the computer I want to use.
| However, I do need to change the input on the monitor as one of
| the them is connected via HDMI.
| harikb wrote:
| You must in the USBC world!
| D13Fd wrote:
| I like it! Thank you for sharing the code!
|
| By the way, I have that same USB switch. I have tried a number of
| them, and that is the fastest I've found. The only major flaw is
| the status lights -- they are too hard to see from far away.
|
| To fix that issue, I drilled a hole in the top of the case, over
| the lights, about the same size as the adjacent power button. I
| put a small piece of foam inside to separate the two lights, and
| covered it with tape. It works perfectly now and it's so much
| easier to see the status from a typical usage angle.
|
| The whole modification took maybe 15 minutes, and I didn't even
| bother disassembling it first.
| haimgel wrote:
| This is an interesting hack, thanks for sharing! I agree the
| status lights are hard to see...
| Bloggerzune wrote:
| https://www.bloggerzune.com/2020/06/make-money-online-withou...
| How to make money online without investment in home,earn Money on
| blogging, earn Money on Fiverr,make money writing online,How can
| I make money online fast and easy without investment,how to earn
| money online without paying anything.
| Havoc wrote:
| > I wrote some software.
|
| And my heart sank.
|
| Zero chance of getting that past corporate laptops that are way
| too locked down for actual code anything beyond VBA
| smabie wrote:
| Then just have corporate buy you a real KVM switch?
| mercora wrote:
| ive done the same on Linux using udev rules and a simple usb
| switch. i use it for a VM with a physical GPU attached and it
| worked great ever since.
| zwayhowder wrote:
| To paraphrase the internet. Sample configs or it didn't happen!
|
| Seriously, I'd love to see this. I have had mixed results with
| udev and no idea where to start to send an input switch command
| to my monitor.
| Splendor wrote:
| Very cool. Will this only work over HDMI?
| moolcool wrote:
| I imagine it will work on any input your display supports
| salex89 wrote:
| I hoped for the actual switch schematics :) .
|
| Offtopic: I wanted to buy this USB switch, but it's hard to get
| on the current market in my country (or available for an absurd
| price). So I started trying to build my own... which was fun, but
| then I understood I need a some USB/MAX chips that are also hard
| to find, and started to cause me frustration instead of fun,
| because I'm not really that good with low-level electronics,
| university was a long time ago. And I was still without my
| switch/hub. So at the end I just chose a 3-pole double-throw
| toggle switch and a couple of USB connectors and wired them up. I
| only need to switch my keyboard, because my mouse is multi-
| device. If I need more, I'll just wire a hub to it. Work is in
| progress, but it can't get simpler than that.
|
| If you're wondering what got complicated, well as far as I read
| and understood, actually breaking a USB connection with solid
| state logic is kind of a pain in the neck if you want to stay
| within the USB parameters, at least for an inexperienced designer
| like me. And you need to build the power supply for the circuit,
| and I didn't want to introduce an external power supply, I wanted
| to piggyback of the USB source. Something this ugreen product
| does not do. So I left this project for another time, when I
| freshen up on my perished knowledge. A mechanical switch just
| switches the lines and that's it.
| mandeepj wrote:
| I was searching for it couple weeks ago. The cheapest KVM for two
| monitors at ebay starts from $80. So, good job.
| brian_herman wrote:
| https://store.level1techs.com/products/kvm-switch-dual-monit... A
| little more expensive. But gets the job done!
| bijant wrote:
| The Headline hit me right in the stomach because it was just
| yesterday that I was pondering whether to build or to order a USB
| Switch. With much to do currently, I wussed out and just ordered
| it. I didnt pay 38$ though:
| https://de.aliexpress.com/item/1005001274095928.html USB 2 is
| more than enough for mouse and keyboard and it has the additional
| advantage of having an extension button to switch.
| mmsimanga wrote:
| I have similar setup without the software to automatically switch
| inputs. I use the physical buttons on the monitor to switch
| input. Not efficient but I get a better resolution than pushing
| display through a cheap KVM switch. Will be trying software in
| article. Anyone know of software that runs on Linux to switch
| display the input? OP lists Windows and Mac OS support.
| pedrocr wrote:
| In Linux you can probably do it with a script that calls
| ddcutil:
|
| http://www.ddcutil.com/
| haram_masala wrote:
| https://www.amazon.com/gp/aw/d/B0817YFJKW
|
| $60 shipped.
| D13Fd wrote:
| That's USB 2 and one monitor. He is looking for USB 3.
|
| Also, I can tell you it's harder than you'd think to find good
| hardware in this area, so I don't think the software effort is
| wasted.
| hbcondo714 wrote:
| Interesting image descriptions. The 6th one says "Suport
| operate system" with a Windows 7, 8 and Vista icons.
| vxNsr wrote:
| that's one monitor
| jen20 wrote:
| This fails at two criteria presented in the second paragraph:
|
| - it only supports one 4K monitor, not two,
|
| - it doesn't support USB-C.
| m0shen wrote:
| This is great! I did something very similar using AutoHotKey and
| Synergy : https://moshen.net/posts/virtual_kvm/
| D13Fd wrote:
| That looks nice! But there are two downsides:
|
| - Your solution requires Synergy. In my experience, Synergy has
| been buggy--or at least extremely finicky--every time I've
| tried it since release circa 2001. When it comes to input
| devices, I want things to be basically flawless. So I like this
| very simple fix better.
|
| - The posted solution is cross-platform between Mac and
| Windows, which is a common use case. Yours relies on
| Autohotkey, which is awesome on Windows but, last I checked,
| terrible on Mac OS.
| kitsunesoba wrote:
| The other thing about Synergy is that it's a bit of a
| question mark in terms of security, even with encryption
| enabled (at least that I've seen -- would be happy to be
| corrected!)
| m0shen wrote:
| Yeah, fair points. Every now and then I have to stop/start
| Synergy for it to work. Since my mouse/keyboard remain
| connected to my Windows machine, it can act as the "server"
| and issue the DCC to the monitor to switch when my key combo
| is hit. So I only ever run it on the Windows box.
| zachrose wrote:
| Would somebody like to help me understand why KVM switches are so
| sophisticated? A DisplayPort cable has 20 pins, so why can't it
| just be a 20 pole switch? (Or 30 pole for two USBs and a
| headphone jack, etc.)
| formerly_proven wrote:
| Using a literal switch or multiplexer would have the link
| disappear, so switching causes ~5-10 seconds of delay, assuming
| the machine doesn't crash or hang because somehow that's okay
| behavior for computers in 2020...?!
|
| Additionally: The DisplayPort spec mandates that operating
| systems have to throw a huge temper tantrum and garble your
| desktop and windows when you disconnect or turn off a display.
| (Yes, nVidia and Microsoft consistently deny implementing an
| option to turn this utterly braindead behavior off, saying that
| it's not a bug, but intended behavior because DisplayPort and
| VESA say so).
|
| What KVMs instead contain is similar to the rescaler ASICs
| found in a monitor, they receive multiple streams of display
| data and mix/forward/scale one of these. But since they
| constantly receive all of the streams, switching can be
| instant, or at least as quick the monitor can modeswitch
| (which, for some reason, takes screens at least a second).
| JoshTriplett wrote:
| Can you provide more information about the details of
| DisplayPort you're referring to, and what actual spec-
| required behavior you're referencing?
| stonogo wrote:
| In addition to the signal issues outlined in sibling comments,
| a good KVM switch presents the HID devices full-time, so
| instead of the computers seeing USB disconnect/reconnects, they
| don't see any difference at all. This requires a complete USB
| implementation including HID protocols and something to
| translate real-keyboard and real-mouse signals into the virtual
| USB devices.
|
| There are similar considerations regarding DDC passthrough on
| monitors for resolution negotiation and so forth.
|
| A bad KVM presents to the computer as though the user is
| disconnecting all the input devices and the monitors every time
| you switch. These are indeed much simpler and cheaper devices
| but they cause all kinds of quality-of-life issues when you use
| them regularly.
| comboy wrote:
| I have one of those bad KVM switches. How do I know which one
| to buy to have a good one?
| formerly_proven wrote:
| Level1 sells KVM switches that are said to be quite good
| for their money.
| zachrose wrote:
| Definitely didn't imagine that KVM switches could actually be
| that good when I asked the question. (I've obviously never
| used one.) Thanks!
| modeless wrote:
| Why shouldn't a computer be able to handle reconnection of
| peripherals without quality of life issues? It's pretty silly
| if this pure software issue is the reason KVM hardware has to
| be so complex and expensive.
| qppo wrote:
| To be honest it probably comes down to being a non trivial
| problem to get it to be perceptually seamless and a rare
| enough event that people don't have the incentive to fix
| it.
|
| Most people aren't plugging/unplugging monitors often
| stonogo wrote:
| Some peripherals require configuration after connection.
| Waiting for this can suck. I'm including monitors here -- a
| bad implementation will present, as an example, monitors
| out of order. Another problem you run into is inadvertently
| cycling through connections too quickly, which can show as
| devices being disconnected during initialization, causing
| some systems to flag the device as malfunctioning and
| refuse to initialize it next connection.
|
| Of course it's easy to say that these are silly problems
| that should have pure software fixes, but Microsoft and
| Apple don't exactly accept patches. Let's not pretend that
| software is optimal.
| aetch wrote:
| You can see for yourself by disconnecting your monitor in a
| multi monitor setup or opening your laptop lid if you use
| the laptop on a dock. Computer windowing systems seem to
| take a moment to reposition all the windows and might not
| remember to redistribute your windows when the monitor
| count changes.
| formerly_proven wrote:
| For many years I was happy with my multi-monitor setups.
| I'd use multiple screens for work, and turn all off
| except the center one for watching movies or playing
| games (because the backlight bleeding of the other
| screens was annoying, even with a 100 % black image).
|
| That's not possible any more. Microsoft, VESA, nVidia say
| no. This mustn't be possible. (Actually it used to be
| possible to add a registry key in Windows 7 that disabled
| all of this bullshit, but Microsoft wisely decided in
| Windows 10 to remove that. It must not be done.)
|
| Turning _compliant_ DisplayPort devices off while using a
| _compliant_ operating system must always garble all
| windows and shuffle desktop icons around. The spec says
| so. So it must be. The will of the ancients.
|
| (nVidia will allow you to turn this off, _if_ you are
| using a Quadro card - then you can use EDID emulation
| even on display-ports, which causes the OS to think the
| display is always connected - and more importantly -
| _turned on_. One of these areas where Linux is ahead --
| although Linux is back to garbling windows like the rest
| in case you do actually decide, as an individual with
| agency, not a compliant operating system, to change the
| arrangement of displays.)
| zachrose wrote:
| Thanks everyone!
| bravo22 wrote:
| Signal integrity. High speed signals degrade with even
| slightest mismatch in trace length or stubs. For high-speed
| signals you use a chip which is essentially an electrical
| repeater to redirect the output to port A or B.
| adrianpike wrote:
| It can be, eBay has HDMI physical switches for like $8. Your
| computers will see it as a monitor unplug, though, and do fun
| things with adjusting windows/icons/resolutions, and then have
| to re-handshake on every switch. Not a blocker, just a pain.
|
| I'm also not 100% sure if it'll freak HDCP out.
| myself248 wrote:
| At the multi-gigabit speeds of a modern video signal, the
| components of a normal mechanical switch are antennas.
| modeless wrote:
| So are the pins in cable connectors, but cables are
| (relatively) cheap and switching signals by replugging
| connectors works just fine.
| formerly_proven wrote:
| In my experience displayport and DVI cables of all brands
| and prices are incredibly fragile and definitely stop
| working well soon if you plug/unplug them once too often.
|
| Too often is something like 20-30 times.
| chrisseaton wrote:
| I think KVMs provide the illusion of the monitor still being
| there when you switch away from that machine? So it doesn't
| think you just yanked the cable.
| Ductapemaster wrote:
| A lot of it has to do with the electrical properties of such a
| switch. Even older versions of DisplayPort have _massive_ data
| rates, meaning each electrical signal switches many millions of
| times a second. Also, each signal may have to switch states
| close to the same time as the other signals, meaning there
| needs to be some sort of matching between the different signal
| paths.
|
| Add in noise sources from the power supplies, your cell phone,
| and other sources, and it becomes a challenging physics
| problem. Not to mention, you don't want those signals leaking
| _out_ either. At these data rates, wires are both transmitting
| and receiving antennas.
|
| Switches are inherently very mechanical devices, so designing
| one that can operate in these conditions reliably would be both
| complex and expensive. Much easier to have some silicon do it
| for you.
| renewiltord wrote:
| Haha, this is clever and I like it. You turned what is usually
| solved on the physical layer to something solved on the logical
| layer - which is almost always better because you can express
| conceptual changes much better when you don't need hardware.
|
| It's a small taste of the stuff that software-defined networks
| have added to networking.
___________________________________________________________________
(page generated 2020-09-02 23:00 UTC)