Keyboard source to input ideas

Projects General Guidance
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I am currently building the MEGA BREAD project for myself and my son to tinker around with.
In the near future, this is to be a base station for robotics control and programming.
The keyboard is a 30 push button switch base with 10 outputs and 3 inputs.
From the below images you can see that the common blue wires on the schematic are the top yellow wires going to the analog input rail. They are each connected to a 3 stack switch setup on the common side.
The 3 feed lines on the right side (Red, Yellow, Blue) are the question.

Is it better to supply the feed lines with a digital source, or just connect them to analog in, or use an actual signal ?

Fritzing forums, by vanepp:
If I understand your circuit correctly what you are trying to do is multiplex 3 sets of 10 push button switches in to 10 input ports. In future it would be more useful to upload the fzz file of the entire sketch which would give us schematic view to more easily verify the connections For this to work one connection on each push button in the vertical direction in the above needs to go to the input port. That seem to be the case. The other connection to the push button in a horizontal row should be connecting all 10 push-buttons in a horizontal row to each other and to one (and only one) of the 3 drive wires I think (if I'm following the wires correctly) that too is true. Now how this works is that you need to have set the pull-up resistors on the input port (or add external pull up resistors to the 10 input lines) so the input port by default is held high. At rest the 3 drive wires need to be driven high from a digital output port. Thus all the input ports will be high even if a switch is pushed. To detect a pushed switch one (and only one!) of the 3 drive wires is set low. Now if a push button in the row that is selected is pressed, the corresponding input port will go low indicating the button is pushed. Thus you want the 3 drive wires to be driven by 3 digital output pins (one for each wire).

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If you don't understand the quoted instructions, please ask more specific questions.

First of all you need digital inputs, not analog ones. If you want to feed the matrix from the 3 feed lines, connect these to 3 digital outputs, and the other 10 lines to digital inputs with internal pullups enabled (mode INPUT_PULLUP).

Then drive each feed output LOW in sequence, and check the inputs. If e.g. feed1 is LOW, and sense5 reads LOW, you know that the button at (1,5) is pressed.

If you happen to press (1,5) and (2,5) together, this will short feed1 and feed2. So you should insert diodes into the feed lines, to protect the output pins against such shorts.

You also can swap the feed and sense lines, using 10 outputs and 3 inputs. This may simplify your code, because you have to check only 3 inputs, but you need 10 diodes to protect the feed outputs.

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Fritzing Forums:
In future it would be more useful to upload the fzz file of the entire sketch which would give us schematic view

I love that the F**ing people also prefer the schematic view.