Logic Level Shifter 8-channel

// Canonical beginner example for an 8-channel logic level shifter
// This sketch demonstrates two shifted digital channels:
// - A4/A5 on the Arduino Uno side (3.3V logic domain via LV1/LV2)
// - D4/D5 on the 5V side (via HV1/HV2)

const int LV_PIN_1 = A4;
const int LV_PIN_2 = A5;
const int HV_PIN_1 = 4;
const int HV_PIN_2 = 5;

void setup() {
  pinMode(LV_PIN_1, OUTPUT);
  pinMode(LV_PIN_2, OUTPUT);
  pinMode(HV_PIN_1, OUTPUT);
  pinMode(HV_PIN_2, OUTPUT);

  Serial.begin(9600);
  while (!Serial) {
    ;
  }

  Serial.println("8-channel logic level shifter demo");
  Serial.println("Toggling two channels on both sides of the shifter.");
}

void loop() {
  // Step 1: set all lines LOW
  digitalWrite(LV_PIN_1, LOW);
  digitalWrite(LV_PIN_2, LOW);
  digitalWrite(HV_PIN_1, LOW);
  digitalWrite(HV_PIN_2, LOW);
  Serial.println("All channels LOW");
  delay(1000);

  // Step 2: set channel 1 HIGH
  digitalWrite(LV_PIN_1, HIGH);
  digitalWrite(HV_PIN_1, HIGH);
  Serial.println("Channel 1 HIGH: A4 <-> D4");
  delay(1000);

  // Step 3: set channel 2 HIGH
  digitalWrite(LV_PIN_2, HIGH);
  digitalWrite(HV_PIN_2, HIGH);
  Serial.println("Channel 2 HIGH: A5 <-> D5");
  delay(1000);

  // Step 4: return everything LOW
  digitalWrite(LV_PIN_1, LOW);
  digitalWrite(LV_PIN_2, LOW);
  digitalWrite(HV_PIN_1, LOW);
  digitalWrite(HV_PIN_2, LOW);
  Serial.println("All channels LOW again");
  delay(1000);
}