deskthority

A question. Is there some type of external controller to add layers to a basic usb keyboard?

A small device with USB input and output would be great. The idea is to use Alt-Gr as a function key and add an extra layer to the navigation cluster, numpad, function keys, etc. Keyboards rotation would be simpler to perform.

Of course it should be programmable. For example with a SPACEFN default implementation or similar. A simple mapping a text ficheo (Soarer mode) would be great.

I don't know if it's technically possible and I guess It will have limitations (distinguish right and left controls for example).

It may be made in the operating system, but would like something that would not have to keep both on Linux, Windows and Mac

Hasu's tmk firmware has a usb to usb “converter”. You can do mostly any mappings and layers with it. No problem with what you described.
If you want something you can buy, I am not sure such a thing exists. Probably too niche

This idea's come up before. It would be highly useful. For instance, I could define a real integrated numpad on my Realforce 87U, so that feature could actually work with OS X. It'd also be great to be able to repurpose the Caps, Num and Scroll Lock LEDs for things like layer indicators.

As far as I know, only Hasu has something you can use. And I'm not sure about the limitations. It involves coding, which slams on the brakes for me. Anyway, his TMK keyboard software project supports a USB to USB converter. It would run on a Teensy.

This is very interesting. I would love to change the layout on my HPE-87 which, despite being a Filco TKL clone, has a different controller and can't be swapped by a bpiphany one.

Just now, searching for Hasu's tmk found a similar thread

Did that one get anywhere either? (On iPhone. Lengthy reads not happening!) I'm sure I've heard people say they tried it. But I never saw a good report of actual use.

He makes/sells a ready made dongle for this or you can buy an arduino/shield and flash TMK to it.

It works really well. Definitely worth it. Your custom keyboard layouts to go!

Who? Got a link?

I wonder if it can handle arbitrary lock light assignments. And if I can understand how to configure it!

https://geekhack.org/index.php?topic=69169.0 from hasu
probably the most sophisticated thing in this direction, but still has its limitations. Connected keyboards work only in 6KRO mode and media keys from the keyboard are not recognized. Basic status LEDs doing fine, nothing more though.

The LEDs thing is hackable rather easily (read: if you are into programming) if you have a specific usecase, I guess. USB host mode for anything else than basic 6KRO is enough work so nobody wanted to look into it further…

It's a bit expensive, 57$ with shipping :/

A Teensy? I'm guessing something else is required to make that price. Bugger.

The dongle is, from what I understood, his own design, hence the price.

a teensy alone doesn't have host-usb, so one can use a arduino shield in addition.
Or you one can buy it assambled, as JotaCe noticed. I am surprised hasu offers to build the converters, on that scale it surely isn't profitable. It is maybe about as much fun as working on the firmware