Multiple Button Matrix wiring

[strikeman2022]

Hello,

I have a general question about Button Matrix with diodes. I currently have 2 button matrices:
Matrix A is a 6x5
Matrix B is a 7x5.

Where 5 is the columns and 6 & 7 are the rows. When I connect Button Matrix A I am able to see button presses without any issues. But when I connect both A and B I am getting phantom button presses.

My question is, how should I be wiring up 2 matrix together. Do I need to connect Matrix A Columns to the end of Matrix B Columns? Or can I just connect them both to the same input pins on the arduino.

[LarryD]

Are you trying to make a 13X5 matrix ?

[strikeman2022]

Yes. That is the goal.

[LarryD]

You will need 13 row pins and 5 column pins.

Similar to this but bigger.

[strikeman2022]

I am with you on that. So my question is can I just connect the top of the columns to the same input pins on arduino. Or do I need to connect top of one matrix to the bottom of the other? Does that make sense?

[jfjlaros]

When you make it a 7×10 matrix (with some missing buttons), you save one pin.

[strikeman2022]

So I guess I am asking if I need todo option A in the following image, as I am doing option B and I am getting phantom presses with specific buttons.

[LarryD]

Above schematic gives 8 X 4

[strikeman2022]

Thanks Larry!

[PaulRB]

@strikeman2022

option A in the following image, as I am doing option B

A and B are electrically identical. Neither A or B should cause ghosting. The ghosting must be because of some other problem.

[LarryD]

And of course 8X5 etc . . .

[strikeman2022]

That's what I initially thought, electrically they seem to be similar. Just not sure why I get phantom presses when both matrix are connected as opposed to single matrix connected.

[PaulRB]

It must be some detail of the circuit or code you have not shared yet.

[kolaha]

13x5 are 18 pins needed
7x10 are 17 pins needed