LED chaser light circuit - using ATtiny85

Write the sketch

Copy and paste this code into the Arduino IDE for the version used in the video.

cpp// Pin mappings on ATtiny85
const int dataPin  = 0;  // PB0 -> SER   (Pin 14 on 74HC595)
const int clockPin = 1;  // PB1 -> SRCLK (Pin 11 on 74HC595)
const int latchPin = 2;  // PB2 -> RCLK  (Pin 12 on 74HC595)

const int stepDelay = 80;    // Milliseconds between steps
const int pauseDelay = 1000; // 1-second pause at the end of the sweep

void updateShiftRegister(byte leds) {
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, MSBFIRST, leds);
  digitalWrite(latchPin, HIGH);
}

void setup() {
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  
  // Clear outputs initially
  updateShiftRegister(0x00);
}

void loop() {
  // 1. Forward sweep: LED 0 to LED 7
  for (int i = 0; i < 8; i++) {
    updateShiftRegister(1 << i);
    delay(stepDelay);
  }

  // 2. Return sweep: LED 6 down to LED 1 (avoids double-hit on ends)
  for (int i = 6; i > 0; i--) {
    updateShiftRegister(1 << i);
    delay(stepDelay);
  }

  // 3. Turn off all LEDs and pause before repeating
  updateShiftRegister(0x00);
  delay(pauseDelay);
}