Summary of 4×4 keypad example using AVR-GCC C language
This article explains a simple method to read a 4x4 keypad using an AVR microcontroller and AVR-GCC. It configures PORTB, splitting it into input rows (pins 0-3) and output columns (pins 4-7). The code sets the high nibble as outputs and enables internal pull-ups for the low nibble. A loop checks for pressed keys by setting column bits to zero and reading row states. 10k resistors are mentioned for protection against shorts.
Parts used in Keypad Reading Project:
- AVR Microcontroller
- 4x4 Keypad
- 10k Resistors
- Port B (PINB0-PINB7)
This is as simple routine how to read 4×4 keypad keys using AVR-GCC language. The keypad is connected to AVR microcontroller 8 bit port. In this example it is B port. You can change ports depending on your needs – this is only an example ant it is not the only way to this.
Howt it works. Well very simply. PORTB is divided into two nibbles PINB0 – PINB3 as inputs (as rows) and PINB4-PINB7 as outputs (columns). The keys are checked in a loop in series. Lets say if we set first row output (PORTB bit 7) to 0 then when checking rows we are looking which bit is set to 0, because of key pressed with function bit_is_set(PINB, bitNo). This function gives non-zero if bit is clear.
10k resistors protect AVR from shortcuts.
#include <avr/io.h>
int main()
{
//high nibble for output(columns) low for input(rows);
DDRB=0xF0;
//enable internal pullups for PB0-PB3
PORTB=0x0F;
//Port D for indication only
DDRD=0xFF;
while (1) //loop key check forever For more detail: 4x4 keypad example using AVR-GCC C language
- Which port is used for the keypad connection?
The example uses Port B, though other ports can be changed based on needs. - How is Port B divided for this project?
Pins 0 through 3 are set as inputs for rows, while pins 4 through 7 are set as outputs for columns. - What function checks if a key is pressed?
The function bit_is_set(PINB, bitNo) is used to check if a bit is clear when a key is pressed. - Why are 10k resistors included in the circuit?
They protect the AVR microcontroller from shortcuts. - What value is assigned to DDRB to configure the port?
DDRB is set to 0xF0 to make the high nibble outputs and low nibble inputs. - How are internal pull-ups enabled in the code?
PORTB is set to 0x0F to enable internal pull-ups for PB0 through PB3. - What is the purpose of Port D in this example?
Port D is configured only for indication purposes.
