Interfacing with Shift Register 74HC595

Using Arduino Project Guidance
#1

Hi, I know that subject is too noob, but I m actually tryng to interface 3 Shift Register in series.

//Pin connected to ST_CP of 74HC595
int latchPin = 0;
//Pin connected to SH_CP of 74HC595
int clockPin = 1;
////Pin connected to DS of 74HC595
int dataPin = 2;

int column_select[25] = {0,1,2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384,32768,65536,131072,262144,524288,1048576,2097152,4194304,8388608};


void setup() {
  //set pins to output so you can control the shift register
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
}

void loop() {
  // count from 0 to 255 and display the number 
  // on the LEDs
  for (int numberToDisplay = 0; numberToDisplay < 26; numberToDisplay++) {
    // take the latchPin low so 
    // the LEDs don't change while you're sending in bits:
    digitalWrite(latchPin, LOW);
    // shift out the bits:
    ShiftOut(dataPin, clockPin, column_select[numberToDisplay]);  

    //take the latch pin high so the LEDs will light up:
    digitalWrite(latchPin, HIGH);
    // pause before next value:
    delay(1000);
  }
}

void ShiftOut(int myDataPin, int myClockPin, int myDataOut) {
  // This shifts 8 bits out MSB first, 
  //on the rising edge of the clock,
  //clock idles low

  //internal function setup
  int i=0;
  int pinState;
  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, OUTPUT);

  //clear everything out just in case to
  //prepare shift register for bit shifting
  digitalWrite(myDataPin, 0);
  digitalWrite(myClockPin, 0);

  //for each bit in the byte myDataOut?
  //NOTICE THAT WE ARE COUNTING DOWN in our for loop
  //This means that %00000001 or "1" will go through such
  //that it will be pin Q0 that lights. 
  for (i=23; i>=0; i--)  {
    digitalWrite(myClockPin, 0);

    //if the value passed to myDataOut and a bitmask result 
    // true then... so if we are at i=6 and our value is
    // %11010100 it would the code compares it to %01000000 
    // and proceeds to set pinState to 1.
    if ( myDataOut & (1<<i) ) {
      pinState= 1;
    }
    else {	
      pinState= 0;
    }

    //Sets the pin to HIGH or LOW depending on pinState
    digitalWrite(myDataPin, pinState);
    //register shifts bits on upstroke of clock pin  
    digitalWrite(myClockPin, 1);
    //zero the data pin after shift to prevent bleed through
    digitalWrite(myDataPin, 0);
  }

  //stop shifting
  digitalWrite(myClockPin, 0);
}

I have made a slight change in “ShiftOut” function as it need to send 3bytes data altogether and simulated it in Proteus.
This program works fine while sending data in first two Shift registers but I dont know what goes wrong when the data is bigger than two bytes(when it goes in third register). i.e. > 65535

#2

when the data is bigger than two bytes(when it goes in third register). i.e. > 65535

How large do you think an "int" is? That should give you a hint.

Rob

#3

Thanks for the reply
I realized that thing after posting this doubt...
So I replaced int with long... Still getting the same error, :frowning:

#4

So I replaced int with long.

Where?

#5 
//Pin connected to ST_CP of 74HC595
int latchPin = 0;
//Pin connected to SH_CP of 74HC595
int clockPin = 1;
////Pin connected to DS of 74HC595
int dataPin = 2;

[b]unsigned long[/b] column_select[25] = {0,1,2,4,8,16,32,64,128,256,512,1024,2048ul,4096ul,8192ul,16384ul,32768ul,65536ul,131072ul,262144ul,524288ul,1048576ul,2097152ul,4194304ul,8388608ul};


void setup() {
  //set pins to output so you can control the shift register
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
}

void loop() {
  // count from 0 to 255 and display the number 
  // on the LEDs
  for (int numberToDisplay = 0; numberToDisplay < 26; numberToDisplay++) {
    // take the latchPin low so 
    // the LEDs don't change while you're sending in bits:
    digitalWrite(latchPin, LOW);
    // shift out the bits:
    ShiftOut(dataPin, clockPin, column_select[numberToDisplay]);  

    //take the latch pin high so the LEDs will light up:
    digitalWrite(latchPin, HIGH);
    // pause before next value:
    delay(1000);
  }
}

void ShiftOut(int myDataPin, int myClockPin, [b]unsigned long[/b] myDataOut) {
  // This shifts 8 bits out MSB first, 
  //on the rising edge of the clock,
  //clock idles low

  //internal function setup
  int i=0;
  int pinState;
  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, OUTPUT);

  //clear everything out just in case to
  //prepare shift register for bit shifting
  digitalWrite(myDataPin, 0);
  digitalWrite(myClockPin, 0);

  //for each bit in the byte myDataOut?
  //NOTICE THAT WE ARE COUNTING DOWN in our for loop
  //This means that %00000001 or "1" will go through such
  //that it will be pin Q0 that lights. 
  for (i=23; i>=0; i--)  {
    digitalWrite(myClockPin, 0);

    //if the value passed to myDataOut and a bitmask result 
    // true then... so if we are at i=6 and our value is
    // %11010100 it would the code compares it to %01000000 
    // and proceeds to set pinState to 1.
    if ( myDataOut & (1<<i) ) {
      pinState= 1;
    }
    else {	
      pinState= 0;
    }

    //Sets the pin to HIGH or LOW depending on pinState
    digitalWrite(myDataPin, pinState);
    //register shifts bits on upstroke of clock pin  
    digitalWrite(myClockPin, 1);
    //zero the data pin after shift to prevent bleed through
    digitalWrite(myDataPin, 0);
  }

  //stop shifting
  digitalWrite(myClockPin, 0);
}

places I have highlighted in bold

#6

Thanks it looks like you got the right places.
This bit:-

//Pin connected to ST_CP of 74HC595
int latchPin = 0;
//Pin connected to SH_CP of 74HC595
int clockPin = 1;

You should not be using pins 0 and 1 for controlling anything as these are used by the serial port and can interfere with loading and serial communication. I would change those.

#7

Anyway that code is rather messy for what it does, try this, just tided it up and not tested, not the change in pin assignment for the shift registers.

//Pin connected to ST_CP of 74HC595
int latchPin = 3;
//Pin connected to SH_CP of 74HC595
int clockPin = 4;
////Pin connected to DS of 74HC595
int dataPin = 2;

unsigned long column_select[25] = {0,1,2,4,8,16,32,64,128,256,512,1024,2048ul,4096ul,8192ul,16384ul,32768ul,65536ul,131072ul,262144ul,524288ul,1048576ul,2097152ul,4194304ul,8388608ul};


void setup() {
  //set pins to output so you can control the shift register
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  digitalWrite(clockPin, LOW);
  digitalWrite(latchPin, LOW);

}

void loop() {
  // count from 0 to 255 and display the number 
  // on the LEDs
  for (int numberToDisplay = 0; numberToDisplay < 26; numberToDisplay++) {
     ShiftOut(column_select[numberToDisplay]);  
    delay(1000);
  }
}

void ShiftOut(unsigned long myDataOut) {
  int pinState;

   for (int i=23; i>0; i--)  {
     digitalWrite(clockPin, LOW);
     if ( myDataOut & (1<<i) ) {
      pinState= 1;
    }
    else {	
      pinState= 0;
    }

    //Sets the pin to HIGH or LOW depending on pinState
    digitalWrite(dataPin, pinState);
    //register shifts bits on upstroke of clock pin  
    digitalWrite(clockPin, HIGH);
  }
    // latch data
    digitalWrite(latchPin, HIGH);
    digitalWrite(latchPin, LOW);
}
#8