/*

http://www.bristolwatch.com/arduino/arduino3.htm
Connecting Arduino to a 74C164 Shift Register
Connected to 7-segment Display
Lewis Loflin lewis@bvu.net

Uses a 74C164 shift register to count from 0 t0 F (HEX) 
on a 7 segment common anode LED display.

To use a common cathode display change line
digitalWrite(data_bit, !k); ->   digitalWrite(data_bit, k); 

connect common to GND

 This program assumes a seven segment display with a bit pattern:
 
Q7 segment a
Q6 segment b
Q5 segment c
Q4 segment d
Q3 segment e
Q2 segment f
Q1 segment g
Q0 segment dp
 
*/
 
 #define data_bit 13 
 #define clk 12 // pin connected to display segment 'a'  
 #define mc 11 // pin connected to display dp pin
 
 
// segment patterns 0 - 9, A - F Hex + dp
byte Digit[] = {0x3f, 0x06, 0x5b, 0x4f, 0x66, 
0x6d, 0x7d, 0x07, 0x7f, 0x67, 0x77, 0x7c, 0x39, 
0x5e, 0x79, 0x71, 0x80};




void setup()   {
  

 
  pinMode(mc, OUTPUT); 
  pinMode(clk, OUTPUT);  
  pinMode(data_bit, OUTPUT);
  

  digitalWrite(mc, 1);  
  digitalWrite(clk, 0); 
  digitalWrite(data_bit, 0);
 
  
 } // end setup


void loop()   {
  int i, j;

  for (i=0; i<= 15; i++)   {
    digitOut(Digit[i]);
    delay(500);
  }

}

void   digitOut(byte j)   {
  byte k;
  for(int i=0; i < 8; i++)   {
    k = j & 0x01;
    digitalWrite(data_bit, !k); 
 // use just k instead of !k for common cathode displays.


    pulsout(clk,1);

    j = j >> 1;
   }
  
}



// toggle the output state on a pin
void toggle(int pinNum) 
{  
  byte pinState = digitalRead(pinNum);
  pinState = !pinState;
  digitalWrite(pinNum, pinState); 
}


// inverts state of pin, delays, then reverts state back
void    pulsout(byte x, int y)   {
  byte z = digitalRead(x);
  z = !z;
  digitalWrite(x, z);
  delayMicroseconds(10* y);
  z = !z; // return to original state
  digitalWrite(x, z);
  return;
} // end pulsout()