Wiring keypad in cube instead of matrix

[Paul_B]

@PaulRB

Why is that? Is the higher voltage drop of a led, compared to other types of diodes, required?

Yes.

OK, I was waiting for aarg, but I will reveal the secret. "Phantom" paths.

@PaulRB

With Charlieplexed key matrices, you can't avoid "phantom" key presses appearing when multiple keys are pressed.

That's it. You can avoid it by selecting the LED voltage such that one LED drop (1.8 V) pulls the logic down (or up if you use it that way) past the threshold, but two LED drops (3.6 V) will not.

For Charlieplexed LED displays, you may have a problem with red LEDs, or with higher than 5 V.

@flashko

In my opinion, this way of connecting is very complicated and unjustified.

Well, your opinion.

@anon57585045

Without diodes, you are right. But with one diode for each key, you would have full n-key rollover.

Ah! Latecomer!

Yes, with red LED diodes.