isolation diodes on each switch ?

[raizur]

I'm new to kb modding, not pc modding (or anything for that) so I'm sure theres probably a fast answer with solid explanation. And other then musical keyboards I find no info on this subject online.

So here it is.

With cost / time of work out of the picture ( not an issue ) what (if any) issues would prevent someone from making a keyboard that has an isolating diode for every single switch. Like that of a music keyboard.
In this way you could avoid needing a single pcb (maybe eliminate pcb entirely) to make any shape wanted. with absolute n-keyroll over aslong as its on ps/2.

[SpAmRaY]

I'm not sure about the KNRO but there is an entire thread dedicated to hard wiring boards etc. Check the making stuff together sub forum.

[dorkvader]

I'm not sure about the KNRO but there is an entire thread dedicated to hard wiring boards etc. Check the making stuff together sub forum.

KRO is limited by two things: the potential key rollover of the matrix, and any limitation of the controller or protocol

Most key matricies are 2KRO, or NKRO, and most keyboard controllers support either NKRO (some PS/2, some USB) or 6KRO (many USB) or 2KRO

Setting up a keyboard with a diode on every switch means the matrix is nkro-compatible. adding either a PS2 controller or a USB controller with compatible firmware will yield a fully NKRO keyboard.

There are many reasons to add NKRO diodes to every switch, and it's especially well suited to DIY designs. Diodes are of cheap enough cost to almost be negligeable, and the only real difficulty is the time investment (either stuffing them into switches, or soldering them to a pcb)

One technique, often called hardwiring has been used to have the diodes themselves be wired between switches, with no PCB. this has been done by many people, but one good early example is lowpoly's apple m0110

Finally, given the proliferation of inexpensive one-off plates, an entire thread has emerged with information and support for direct wiring (or hardwiring of custom keyboard designs:
http://geekhack.org/index.php?topic=40567.0

In short: Other than the added complexity, time, and a little cost, there's nothing preventing you from adding diodes to every switch. I'll most likely be doing this later with a few hall effect keyboards I have.

[Daniel Beardsmore]

With cost / time of work out of the picture ( not an issue ) what (if any) issues would prevent someone from making a keyboard that has an isolating diode for every single switch. Like that of a music keyboard.

How about this one — each switch has a rubber dome inside, yet they went to the trouble of putting diodes in for NKRO:



Zenith Supersport SX keyboard

I picked this photo as it's the clearest illustration I have of a keyboard with diodes.

I just learnt earlier that the Chicony KB-5161A (with its own FCC ID ending in KB-5151A) is the N-key rollover version of the KB-5161. (Ditto for 5152.) The photos only show the extra solder points; the diodes are not in any of the pictures.

There are several options. Marquardt linear switches have the diode inside. Cherry MX switches have space inside for a diode, "jumper" (bridge wire) or LED. If the switch lacks internal space for one, the diode goes on the PCB. I've even seen the diodes outside on the PCB even with Cherry MX switches, probably as it's easier to route the PCB with the diodes able to be positioned at will.

Some switches have three or four legs (e.g. Futaba clicky, Omron and KPT (3), NMB Hi-Tek (4)); I'm still curious if you could make a multi-sensing matrix that achieves NKRO that way.

There are plenty of keyboards on sale today with diode NKRO including the Cherry G8-3850 "MX-BOARD 3.0" (2.0 was 2KRO), Filco Majestouch (NKRO models), and Matias Tactile Pro/Quiet Pro. Note that depending on the controller and interface, you may only get 6KRO due to the limitation of the conventional USB keyboard communication. Some keyboards allow a USB to PS/2 adapter to be connected, and they swap over to PS/2 and provide true NKRO. Some newer keyboards achieve higher numbers of concurrent keystrokes over USB via several different means.

Capacitive keyboards (e.g. Topre Realforce) are NKRO for a whole other set of reasons.