7segShiftRegTest.ino

#define SHIFTDATA 11
#define SHIFTCLOCK 13
#define SHIFTLATCH 10

// the setup routine runs once when you press reset:
void setup() {
  // open a serial port
  Serial.begin(9600);
  
  // set up shift register pins
  // serial data
  pinMode(SHIFTDATA, OUTPUT);
  digitalWrite(SHIFTDATA, LOW);
  // serial clock
  pinMode(SHIFTCLOCK, OUTPUT);
  digitalWrite(SHIFTCLOCK, LOW);
  // latch
  pinMode(SHIFTLATCH, OUTPUT);
  digitalWrite(SHIFTLATCH, LOW);
}

// the loop routine runs over and over again forever:
// seven segment:  0, 1, 2,  3,    4,   5,   6,  7,   8,   9
byte digit[10] = {63, 6, 91, 79, 102, 109, 125,  7, 127, 103};
int d = 0;
void loop() {
  Serial.println(digit[d]);
  shiftData(digit[d]);
  d++;
  if (d >= 10) {
    d = 0;
  }
  delay(500);
}

void shiftData(byte b) {
  // loop through bits 0 - 7 of byte b 
  for (int i=7; i>=0; i--) {
    // set data to high or low depending on bit
    // google 'bitwise and' to see what '&' does
    // google 'bit shift' to see what << does
    // if evaluates true if not zero, false if zero
    if (b & (1<<i)) {
      digitalWrite(SHIFTDATA, HIGH);
      Serial.print(1);
    }
    else {
      digitalWrite(SHIFTDATA, LOW);
      Serial.print(0);
    }
    // pulse the clock line
    digitalWrite(SHIFTCLOCK, HIGH);
    digitalWrite(SHIFTCLOCK, LOW);
  } 
  // latch the data from the shift register to the output register
  // pulse latch
  digitalWrite(SHIFTLATCH, HIGH);
  digitalWrite(SHIFTLATCH, LOW);
  Serial.println();
}