I have a 4x4 matrix for 16 buttons. Each row/column is directly connected to the pins of an unknown microcontroller. When I connect the pins directly to each other, the microcontroller behaves correctly, as if the respective button was pressed.
I want to control the pins directly with an Arduino or connect them directly to GND/VCC. However, when I turn them on this way, the microcontroller either:
- does nothing
- behaves as if several buttons are pressed at once.
Why is that? Am I missing something, like pullup-resistors?
The microcontroller supports certain button presses at the same time. I think it has to do with the row scanning. <- This turned out to be true, the microcontroller checked one row at the time. So it was necessary to activate the column pin only when the right row was selected.