Arduino - ShftIn22

//  Name    : shiftIn Example 2.2                               //
//  Author  : Carlyn Maw                                        //
//  Date    : 25 Jan, 2007                                      //
//  Version : 1.0                                               //
//  Notes   : Code for using a CD4021B Shift Register       //
//          :                                                   //

//define where your pins are
int latchPin = 8;
int dataPin = 9;
int clockPin = 7;

//Define variables to hold the data
//for each shift register.
//starting with non-zero numbers can help
byte switchVar1 = 72;  //01001000
byte switchVar2 = 159; //10011111

//define an array that corresponds to values for each
//of the first shift register's pins
char note2sing[] = {

  'C', 'd', 'e', 'f', 'g', 'a', 'b', 'c'};

//define an array that has a place for the values of
//pins 1-7 (not 0) of the second shift register's
//pins. Not 0 because that will be used as a flag value
byte settingVal[] = {

  0, 0, 0, 0, 0, 0, 0};

//a flag varible used to track whether the program
//is in a setting update mode or not
byte settingSwitch = 0;

void setup() {

  //start serial


  //define pin modes

  pinMode(latchPin, OUTPUT);

  pinMode(clockPin, OUTPUT);

  pinMode(dataPin, INPUT);


void loop() {

  //Pulse the latch pin:

  //set it to 1 to collect parallel data


  //set it to 1 to collect parallel data, wait


  //set it to 0 to transmit data serially


  //while the shift register is in serial mode

  //collect each shift register into a byte

  //the register attached to the chip comes in first

  switchVar1 = shiftIn(dataPin, clockPin);

  switchVar2 = shiftIn(dataPin, clockPin);

  //Print out the results.

  //leading 0's at the top of the byte

  //(7, 6, 5, etc) will be dropped before

  //the first pin that has a high input


  Serial.println(switchVar1, BIN);

  Serial.println(switchVar2, BIN);

  //This for-loop steps through the byte

  //bit by bit which holds the shift register data

  //and if it was high (1) then it prints

  //the corresponding location in the array

  for (int n=0; n<=7; n++)


    //so, when n is 3, it compares the bits

    //in switchVar1 and the binary number 00001000

    //which will only return true if there is a

    //1 in that bit (ie that pin) from the shift


    if (switchVar1 & (1 << n) ){

      //print the value of the array location




//This is a away to examine the whole
//byte at once and create combinations
//of settings.

//By passing the switchVar1 variable to
//a "switch" statement and comparing it against
//a set nemerical value (written in binary)
//you can create special cases

  switch (switchVar1) {

  case 0b00101010:

    Serial.println("D minor");


  case 0b00010101:

    Serial.println("C major");


  case 0b01010100:

    Serial.println("E minor");


  case 0b00101001:

    Serial.println("F major");


  case 0b01010010:

    Serial.println("G major");


  case 0b00100101:

    Serial.println("A minor");


  case 0b01001010:

    Serial.println("B diminished");



    // if nothing else matches, do the default

    Serial.println("Play It, Joe");


// This is a more complicated behavior

//If the switch attached to pin 7 is High

  if (switchVar2 & (1 << 7) ){

    //print"Check, Check" to let us know the settings are being updated"

    Serial.println("Check, Check");

    //set a flag variable to let the progam know the settings are being updated

    settingSwitch = 1;

    //While the switch attached to seven is high,

    //take the bottom 7 bits and load them into

    //an array for easy access later.

    for (int v=6; v>=0; v--)


      if (switchVar2 & (1 << v) ){

        settingVal[v] = 1;


      else {

        settingVal[v] = 0;




  //if the switch is low

  else {

    //and if it was high the very last time it came through

    //this if statement (indicated by the settingSwitch variable still

    //set to "1")

    if (settingSwitch) {

      //turn off the settingSwitch variable


      //Print out the current settings


      for (int s=0; s<=6; s++)


      //Print out the setting names

      //this is being done as a case statement because

      //there weren't built in string arrays yet

      //in Arduino as of Feb. 2007

        switch (s) {

        case 0:



        case 1:

          Serial.print("Octave Shift");


        case 2:



        case 3:



        case 4:



        case 5:



        case 6:




          // if nothing else matches, do the default

          Serial.println("Not Defined");


        //Print Status

        if (settingVal[s]) {

          Serial.print(" On");


        else {

          Serial.print(" Off") ;


         //white space





//white space
//delay so all these print satements can keep up.


//------------------------------------------------end main loop

////// ----------------------------------------shiftIn function
///// just needs the location of the data pin and the clock pin
///// it returns a byte with each bit in the byte corresponding
///// to a pin on the shift register. leftBit 7 = Pin 7 / Bit 0= Pin 0
byte shiftIn(int myDataPin, int myClockPin) {

  int i;

  int temp = 0;

  int pinState;

  byte myDataIn = 0;

  pinMode(myClockPin, OUTPUT);

  pinMode(myDataPin, INPUT);
//we will be holding the clock pin high 8 times (0,..,7) at the
//end of each time through the for loop

//at the begining of each loop when we set the clock low, it will
//be doing the necessary low to high drop to cause the shift
//register's DataPin to change state based on the value
//of the next bit in its serial information flow.
//The register transmits the information about the pins from pin 7 to pin 0
//so that is why our function counts down

  for (i=7; i>=0; i--)


    digitalWrite(myClockPin, 0);


    temp = digitalRead(myDataPin);

    if (temp) {

      pinState = 1;

      //set the bit to 0 no matter what

      myDataIn = myDataIn | (1 << i);


    else {

      //turn it off -- only necessary for debuging

     //print statement since myDataIn starts as 0

      pinState = 0;


    //Debuging print statements


    //Serial.print("     ");

    //Serial.println (dataIn, BIN);

    digitalWrite(myClockPin, 1);


  //debuging print statements whitespace


  //Serial.println(myDataIn, BIN);

  return myDataIn;