11.05.2014 Shift Register on ATmega328 plain C - lightshow

/*
 * Shift Register 74HC595 Test
 * main.c
 *
 *  Created on: 11.05.2014
 *      Author: koepi
 *
 * A0: DS (serial data input)
 * A1: ST_CP (storage register clock pin, latch)
 * A2: SH_CP (shift register clock pin)
 *
 * A0-A2 are PORTC bits 0 - 2, bitmask 0b00000111 -> 0x07
 */

#include "main.h"
#include <avr/io.h>

void setup (void) {
    DDRC |= 0x07;  // data direction register - OUTPUT
    PORTC &= ~(0x07);  // data register - all pins LOW
}

int main (void) {
    setup();
    // writing to 74HC595 should work like this:
    // set bit on DS (A0), then toggle SH_CP.
    // after 8 bits, toggle latch to view result.

    while (1) {  // endless loop
        char i=0;
        int dyn = 15;
        for (int j=0; j<8; j++) {
            i = (1 << j);
            write_reg(i);
            dyn+=5;
            delay(dyn);
        }
        for (int j=7; j>=0; j--) {
            i = (1 << j);
            write_reg(i);
            dyn-=5;
            delay(dyn);
        }
        i=0;
        for (int j=0; j<8; j++) {
            i |= (1 << j);
            write_reg(i);
            dyn+=5;
            delay(dyn);
        }
        for (int j=7; j>=0; j--) {
            i &= ~(1 << j);
            write_reg(i);
            dyn-=5;
            delay(dyn);
        }
        for (int j=0; j<8; j++) {
            i = (1 << j);
            write_reg(i);
            delay(10);
            write_reg(!(i));
            delay(10);
            dyn+=5;
            delay(dyn);
        }
        for (int j=7; j>=0; j--) {
            i = (1 << j);
            write_reg(i);
            delay(10);
            write_reg(!(i));
            delay(10);
            dyn-=5;
            delay(dyn);
        }
        i=0;
        for (int j=0; j<8; j++) {
            i |= (1 << j);
            write_reg(i);
            dyn+=5;
            delay(dyn);
        }
        for (int j=7; j>=0; j--) {
            i &= ~(1 << j);
            write_reg(i);
            dyn-=5;
            delay(dyn);
        }
        int del=1;
        int inc=1;
        for (int j=0; j<400; j++) {
            del+=inc;
            if (del<=0 || del> 7) inc=-inc;
            i=0xff;
            write_reg(i);
            delay(del);
            i=0x00;
            write_reg(i);
            delay(del);
        }
    }

}

void write_reg(char reg) {
    PORTC &=~(0b00000010);  // switching off latch
    for (int i=7; i>=0; i--) {
        if (reg & (1 <<i)) {
            PORTC |= 0b00000001;  // setting DS
        } else {
            PORTC &=~(0b00000001);  // resetting DS
        }
        PORTC |= 0b00000100;  // SH_CP HIGH
        PORTC &= ~(0b00000100);  // SH_CP low
    }
    PORTC |= 0b00000010;  // switching on latch
}

void delay (int ms) {
    for (int i=0; i<ms; i++) {
        for (int j=0; j<1600; j++) {
            asm volatile ("nop");
        }  // 16000 nops at 16 MHz = 1kHz
    }
}