attiny85_shift_register - displays digits 0 through 9 on 7-seg LED using 74HC595 for I/O expansion

main.c

/*
 * attiny85_shift_register - displays digits 0 through 9 on 7-seg LED using 74HC595 for I/O expansion
 * 
 * [ATtiny85 AVR] ==> [74HC595 shift register] ==> [7-seg led display]
 */

#include <avr/io.h>
#include <util/delay.h>

// serial data-in
#define ser PB3

// register clock
#define rclk PB2

// serial clock
#define srclk PB4

// serial clear (active-low)
#define srclr PB1

#define delayTime 250

//==========================================================================
// ATtiny85 pin summary			other functions
//
// pin 1 is PortB bit 5 (PB5)	(PCINT5/RESET/ADC0/dW)
// pin 2 is PortB bit 3 (PB3)	(PCINT3/XTAL1/CLKI/OC1B/ADC3)
// pin 3 is PortB bit 4 (PB4)	(PCINT4/XTAL2/CLKO/OC1B/ADC2)
// pin 4 is GND
// pin 5 is PortB bit 0 (PB0)	(MOSI/DI/SDA/AIN0/OC0A/OC1A/AREF/PCINT0)
// pin 6 is PortB bit 1 (PB1)	(MISO/DO/AIN1/OC0b/OC1A/PCINT1)
// pin 7 is PortB bit 2 (PB2)	(SCK/USCK/SCL/ADC1/T0/INT0/PCINT2)
// pin 8 is VCC
//==========================================================================

void outputPattern(uint8_t);

uint8_t digitPattern[] = {
	0x6F, //0b01101111 "0"
	0x03, //0b00000011 "1"
	0x76, //0b01110110 "2"
	0x37, //0b00110111 "3"
	0x1B, //0b00011011 "4"
	0x3D, //0b00111101 "5"
	0x7D, //0b01111101 "6"
	0x07, //0b00000111 "7"
	0x7F, //0b01111111 "8"
	0x3F  //0b00111111 "9"
};

int main(void) {
	
	//DDRB |= ((1 << rclk) | (1 << ser) | (1 << srclk) | (1 << srclr));
	DDRB |= ((1 << rclk) | (1 << ser) | (1 << srclk));
	PORTB = 0x00;
	
	// instead can just connect srclr to AVR reset pin and let it clear the 74HC595
	//PORTB |= (1 << srclr); 
	
	for (;;) {
		for (int i=0; i<10; i++) {
			outputPattern(digitPattern[i]);
			_delay_ms(delayTime);	
		}
	}
	
	return 0; 
}

void outputPattern(uint8_t pattern) {
	PORTB &= ~(1 << rclk);
	
	for (int i = 0; i < 8; i++) {
		uint8_t dataBit = (((pattern & (1 << i)) >> i));
		
		PORTB &= ~(1 << srclk);
				
		if (dataBit) 
			PORTB |= (1 << ser);
		else
			PORTB &= ~(1 << ser);
			
		PORTB |= (1 << srclk);
		
		PORTB &= ~(1 << ser);
	}

	PORTB |= (1 << rclk);
}