int pin_LED = 2;

int pin_SDA = 0;
int pin_SCL = 1;

void start() {
  digitalWrite(pin_SDA, HIGH);
  delay(10);
  digitalWrite(pin_SCL, HIGH);
  delay(10);
  digitalWrite(pin_SDA, LOW);
  delay(10);
  digitalWrite(pin_SCL, LOW);
}

void stop() {
  digitalWrite(pin_SDA, LOW);
  delay(10);
  digitalWrite(pin_SCL, HIGH);
  delay(10);
  digitalWrite(pin_SDA, HIGH);
  delay(10);
}

int send(int value) {
  for(int i = 0; i < 8; i++) {
    if(value & 0x80) 
      digitalWrite(pin_SDA, HIGH);
    else 
      digitalWrite(pin_SDA, LOW);
    digitalWrite(pin_SCL, HIGH);
    delay(1);
    value <<= 1;
    digitalWrite(pin_SCL, LOW);
  }
  digitalWrite(pin_SDA, HIGH);
  digitalWrite(pin_SCL, HIGH);
  delay(1);
  pinMode(pin_SDA, INPUT);
  int ACK = digitalRead(pin_SDA);          // possible ACK bit
  pinMode(pin_SDA, OUTPUT);
  digitalWrite(pin_SCL, LOW);
  return ACK;
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello!");

  pinMode(pin_SDA, OUTPUT);
  pinMode(pin_SCL, OUTPUT);
  pinMode(pin_LED, OUTPUT);

  delay(100);
  start();
  int value = 0x27 << 1;
  Serial.println(send(value));
  value = 0x7E << 1;
  Serial.println(send(value));
  stop();
}

void loop() {
  // digitalWrite(pin_LED, HIGH);   // bật đèn led
  // delay(1000);                  // dừng trong 1 giây
  // digitalWrite(pin_LED, LOW);    // tắt đèn led
  // delay(1000);                  // dừng trong 1 giây
}