Question

In reading the columns of a keyboard matrix, when no key is pressed then all the pins show?

(a) 0

(b) 1

(c) F

(d) 7

This question was posed to me during a job interview.

My question comes from Keyboard Interfacing topic in chapter AVR Microcontroller of Microcontroller

Answer 1

The correct answer is:

(b) 1

In a keyboard matrix, when no key is pressed, all the column lines typically read as 1 (high) due to pull-up resistors on the input lines. When a key is pressed, it creates a connection that brings the specific row-column intersection to 0 (low), allowing the microcontroller to detect which key was pressed.