/*
so far, no need for any code
*/

# define CLK 2
# define DAT 3

void sendBargraphOLD(uint8_t value) {
  value &= 0x0f;

  for (uint8_t bit = 0; bit < 4; bit++) {
    digitalWrite(DAT, value & 0x01);

    digitalWrite(CLK, HIGH);
    digitalWrite(CLK, LOW);

    value >>= 1;
  }
}

void sendBargraph(uint8_t value) {
  value &= 0x0f;

  // Five-zero preamble
  for (uint8_t bit = 0; bit < 5; bit++) {
    digitalWrite(DAT, LOW);
    digitalWrite(CLK, HIGH);
    digitalWrite(CLK, LOW);
  }

  // Start bit
  digitalWrite(DAT, HIGH);
  digitalWrite(CLK, HIGH);
  digitalWrite(CLK, LOW);

  // Four data bits, LSB first
  for (uint8_t bit = 0; bit < 4; bit++) {
    digitalWrite(DAT, value & 0x01);

    digitalWrite(CLK, HIGH);
    digitalWrite(CLK, LOW);

    value >>= 1;
  }
}

void setup() {
  pinMode(CLK, OUTPUT);
  pinMode(DAT, OUTPUT);
}

int value;

void loop() {
  sendBargraph(value);
  value++; if (value > 7) value = 0;

  delay(20);
}