Tutorial.ShftIn13 History

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September 14, 2015, at 02:37 PM by Arturo -
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February 06, 2007, at 11:43 PM by Carlyn Maw -
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byte shiftIn(int myDataPin, int myClockPin) {

  int i;
  int temp = 0;
  int pinState;
  byte myDataIn = 0;

  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, INPUT);
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} @]


} @]

February 06, 2007, at 10:27 PM by Carlyn Maw -
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// Date : 25 Oct, 2006 //


// Date : 25 Jan, 2007 //

February 06, 2007, at 10:24 PM by Carlyn Maw -
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//  Name    : shiftIn Example 1.3                               //
//  Author  : Carlyn Maw                                        //
//  Date    : 25 Oct, 2006                                      //
//  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 shift register.
//starting with a non-zero numbers can help
byte switchVar1 = 72;  //01001000

//define an array that corresponds to values for each 
//of the shift register's pins
char note2sing[] = {
  'C', 'd', 'e', 'f', 'g', 'a', 'b', 'c'}; 

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);

  //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);

  //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 following 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 B00101010:
    Serial.println("D minor");
  case B00010101:
    Serial.println("C major");
  case B01010100:
    Serial.println("E minor");
  case B00101001:
    Serial.println("F major");
  case B01010010:
    Serial.println("G major");
  case B00100101:
    Serial.println("A minor");
  case B01001010:
    Serial.println("B diminished");
    // if nothing else matches, do the default
    Serial.println("Play It, Joe"); 

//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
//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;