/* 
 * 7HC595 4-Digit Diagnostic Test
 * Displays the same digit (0-9) on all modules at once.
 */

const int DATA_PIN  = 11;  // DS
const int LATCH_PIN = 12;  // STCP
const int CLOCK_PIN = 13;  // SHCP

// Segment map for 0–9 (Common Cathode)
// Bit order: DP G F E D C B A
const byte DIGIT_MAP[10] = {
  0b00111111, // 0
  0b00000110, // 1
  0b01011011, // 2
  0b01001111, // 3
  0b01100110, // 4
  0b01101101, // 5
  0b01111101, // 6
  0b00000111, // 7
  0b01111111, // 8
  0b01101111  // 9
};

void setup() {
  pinMode(DATA_PIN, OUTPUT);
  pinMode(LATCH_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
}

// Sends the same byte to all 4 shift registers
void sendToAll(byte pattern) {
  digitalWrite(LATCH_PIN, LOW);
  
  // Shift out the same pattern 4 times
  for (int i = 0; i < 4; i++) {
    shiftOut(DATA_PIN, CLOCK_PIN, MSBFIRST, pattern);
  }
  
  digitalWrite(LATCH_PIN, HIGH);
}

void loop() {
  // Cycle through numbers 0 to 9
  for (int num = 0; num <= 9; num++) {
    
    // Test 1: Display the number without Decimal Point
    sendToAll(DIGIT_MAP[num]);
    delay(800);
    
    // Test 2: Display the number WITH Decimal Point (checks bit 7)
    sendToAll(DIGIT_MAP[num] | 0b10000000);
    delay(200);
  }
}