How does NKRO over USB work?

[UselessBread]

I am wondering how N key roll over over USB works, as some keyboards like the duckys or Noppoos have it. What limits the 'regular' keyboard to 6 key roll over via USB?

If you know the answer, please go ahead and explain it on a level that would allow me to make a controller that supports nkro and 6kro.

[WorldDominator]

I remembered this at one point…I have a ducky dk9087 and I know I had to turn NKRO off on my iMac because OSX can only do 6 key roll over for some reason. I wish I remembered… :P

[TheProfosist]

The cheaper Chinese keyboards emulate multiple keyboards to do this in many cases. Some other bands use modified protocols. The new better ones just use full speed usb (yes full speed not even high speed) and problem solved. As for what limits a usb keyboard to 6KRO that would be the original low speed protocol. You dont need to make a controller there are already a few devices that do it properly using full speed, though i dont remember them off hand, you can search GeekHack and find them probably fairly easy. But if you just want a controller the teensy will do it fine all you need is the correct firmware and at least 2 different peoples support this feature. The are some restrictions the main one being you have to toggle it on once booted or you wont be able to use your keyboard in your BIOS, though it should work in UEFI.

[UselessBread]

The cheaper Chinese keyboards emulate multiple keyboards to do this in many cases. Some other bands use modified protocols. The new better ones just use full speed usb (yes full speed not even high speed) and problem solved. As for what limits a usb keyboard to 6KRO that would be the original low speed protocol. You dont need to make a controller there are already a few devices that do it properly using full speed, though i dont remember them off hand, you can search GeekHack and find them probably fairly easy. But if you just want a controller the teensy will do it fine all you need is the correct firmware and at least 2 different peoples support this feature. The are some restrictions the main one being you have to toggle it on once booted or you wont be able to use your keyboard in your BIOS, though it should work in UEFI.

Yeah I was thinking about making my own keyboard after I undertstood how a key-matrix works. I would be using a Teensy.

 

So If I understand it correctly, the difference between NKRO and 6KRO keyboards is that the controllers of the NKRO ones firmware supports the full speed of USB 2.0?

[TheProfosist]

Yeah I was thinking about making my own keyboard after I undertstood how a key-matrix works. I would be using a Teensy.

 

So If I understand it correctly, the difference between NKRO and 6KRO keyboards is that the controllers of the NKRO ones firmware supports the full speed of USB 2.0?

 

With the teensy much of the work is already done for you all you would have to do is change the layout in the firmware of your choosing pertaining the PCB you create is done correctly. There is a bunch of info on this topic on GeekHack and Deskthority.

 

In some of the newer cases yes but in most retail cases no they use some other method to get around it usually, one of the ones I mentioned previously. Some of the newer ones that have come out and are coming out use this method but it not where near majority currently on retail products for achieving NKRO over usb. As for the teensy it fully supports this method but it has to be programmed into the firmware that your using.