Recommended ROWS x COLUMS

[vHugo]

One quick question ¿How many rows and colums does a 69 key keyboard need?

With my maths 7x10 will be enough but if I use the CAD applications from qmk to build the wiring it jumps to 5x15.... 17 pins vs 20 pins why?

Thanks for your time!!

[nevin]

Depends on how complicated you want to make your matrix. The default & easiest way is to wire it like it is physically. 5 rows x 15 columns. It takes up more pins but is easier to wire and keep straight in the firmware. For 70 keys you could actually squash it down to 8x9. Square matrices are more pin efficient, but harder to unravel in firmware.

[Applet]

Since you were suggested 5x15, I'm guessing you are doing a keeb with 5 rows and 15 keys wide. If you have enough pins, 5x15 is likely the way to go, or 10x8 by doing a "duplex matrix" (https://wiki.ai03.com/books/pcb-design/page/matrices-and-duplex-matrix). You can do this even more efficient by doing a "japanese duplex" (https://kbd.news/The-Japanese-duplex-matrix-1391.html). Both of these alternatives adds more complexity compared to the 5x15 like nevin says, both in firmware and PCB design.