ATMega32 Simple Multiplexing Display Example

In this programming example, I will show a very simple display multiplexing using a two-digit seven-segment display. It will show a value that read from the lower nibble of PortB.

Program Simulation

The display is common cathode type. I use a resistor network to cut down its forward current. The 74HC04 chip replace driving transistors, due to simulation difficulty. The lower nibble of PortB reads the digital inputs from a DIP switch. We will not need additional resistors because all input pins are turned high via software.

/*
 * muxDisplayDigitalRead.c
 *
 * Created: 5/30/2022 6:19:32 PM
 * Author : dell
 */ 
 
#include <avr/io.h>
 
#define F_CPU 4000000UL
#include <util/delay.h>
 
int main(void)
{
    unsigned char temp;
	/*Common Cathode Display*/
unsigned char displayData[10]={0x3F,0x06,0x5B,0x4F, 
0x66,0x6D,0x7D,0x07,0x7F,0x6F};
	/*PortB Input*/
	DDRB=0x00;
	/*Turn on PD0...3 of PortB*/
	PORTB=0x0F;
	/*PortB and PortD Output*/
	DDRC=0xFF;
	DDRD=0xFF;
    while (1) 
    {
		/*Read PortB*/
		temp=PINB&0x0F;
		/*Multiplexing Display Process*/
		PORTD=0x00;
		PORTC=displayData[temp/10];
		/*Turn On Digit 1*/
		PORTD=0x01;
		/*Activate for 5ms*/
		_delay_ms(5);
 
		PORTD=0x00;
		PORTC=displayData[temp%10];
		/*Turn On Digit 2*/
		PORTD=0x02;
		/*Activate for 5ms*/
		_delay_ms(5);
    }
}
 
 

 Click here to download its source file.

Schematic Diagram

We can multiplex multi-digit 7-Segment display using the SN74HC168 serial to parallel shift registers chip.