Keypad/keyboard interface to STM32F0

This module explains how to use 4x3 Membrane Keypad with STM32F0-DISCOVERY microcontroller board Requirements: 1. 4x3 Membrane Keypad 2. Seven segment display & 3K3ohms resistors 3. Connecting wires. 4. General purpose printed circuit board. Keypad is an array of switches. Matrix keypads are very common input devices in embedded systems. They have simple architecture and are easy to interface. One good thing about them is that they allow you to interface a large number of input keys to a microcontroller with minimum usage of I/O resources. This tutorial type module explains how to read input data from a 3×4 (12 keys) matrix keypad interfaced to an ARM Cortex M0 based STM32F0 microcontroller embedded board and display on a seven segment display. In short this project is to display the pressed key on the seven segment display.
Working: There will be 2 wires connected to each switch of the keypad, they get short circuited whenever a button is pressed. For example; when button '1' is pressed, pin PB1 and pin PB2 are connected (as shown in the picture below). Normally when no switch is pressed there is no connection between rows and columns. Whenever a button is pressed contact is made between particular row and column. 4x3 Keypad pin can be direct...