Hacker News Reader

Comment by zenlot | Hacker News Reader

For those lucky to have VGA port, I've recently did a setup with iPad 3 as second display for laptop [0] with VGA and a few resistors to create dummy display.

[0] https://blog.zenlot.xyz/post/ipad_second_display/

View on HN

Cool hack, but is that seriously the easiest way to ask Windows for a second display? That is nuts!

Yeah, "add virtual ___" is one of the hardest and most complicated thing in Windows, probably worse on macOS, definitely where FOSS OS shine.

For Windows "software display" driver implementations, from top of my head there are DisplayLink, Fresco Logic FL2K driver, and a homebrew one by q61.org[1] but none are open sourced.

1: http://q61.org/en/chibimo/build/

Of those, I’ve had the longest (since 2007 and then 2009) and most reasonably reliable experience with the DisplayLink family, to the point that I look for that and avoid alternatives. For example, USB parts from Startech, Targus, Belkin, Kensington, and Plugable leverage DisplayLink.

Thanks! I didn't find a way to create a dummy display with native Win10 tools. There was a way to do it in previous minor releases, but with recent Win10 updates Microsoft has removed it or disabled. So went for a hardware solution instead, as I didn't want to install any 3rd party software. That's quite reliable solution, just need to be careful if moving laptop too much :)

You can buy dummy headless display dongles very cheaply, e.g.: https://www.amazon.co.uk/Headless-Display-Emulator-Headless-...

But why do you need hardware for this? Surely this is a purely software problem.

https://github.com/microsoft/Windows-driver-samples/tree/mas...

Yea, they want to get rid of that but need to know more about how to handle it in the lower levels of the OS (mentioned on the github page).

macOS is a pain as well. There was a fairly well documented way (in the open source world) of writing a stub driver to create a virtual display. Apple axed it without notifying anyone when their own "Use an iPad as a second screen" support came out. All the third party apps that provided that function broke overnight, notably Duet Display.

Considering Duet works again, I wonder if the mechanism they use was quietly shared with them or if it was publicly shared.

Had to do this years ago for headless bitcoin miners with multiple GPUs.

I see that there are HDMI and DVI-D dummy adapter editions, but they're a lot more expensive. I wonder if you could just get a cheap mass-produced HDMI-->VGA or DVI-VGA adapter and then push in resistors to save a few bucks.

With DVI-I, the resistor trick should work (it's just VGA), but not as easy as just folding some 1cent resistors around.

https://www.geeks3d.com/20091230/vga-hack-how-to-make-a-vga-...

Reply on news.ycombinator.com