Finally, a three some (74HC595)!

As a follow up to the first tests with the 74HC594 and 74HC595 with Arduino I got some more 595 delivered, finally chaining them together. This example uses the 74HC595 chip.

 

Download: fritzing  sketch, fritzing 74HC595 part.

Code:

First, you need to install (extract) the MM74HC595 library I wrote into your "<\libraries>" folder.

/**
 * Board: Pro Mini 5V
 * 
 * Chained 74HC595 8 bit shift register demo. Knight Rider!
 *
 * $Id: test_74HC595.pde 319 2011-10-13 20:48:10Z wunderlins $
 */

// how many shift registers are we using in serie? (must be >=1)
#define NUM_SHIFT_REGISTERS 3

// include library (must be installed unter <sketches>/libraries/MM74HC595/)
// http://spliffy.freeshell.net/hardware/MM74HC595.zip
#include <MM74HC595.h>

/**
 * Arduino pins:
 * 
 * PIN_SER: is the arduino serial pin
 * PIN_SCK: is the arduino pin for the shift register
 * PIN_RCK: is the arduino pin for the output register
 */
int PIN_SER = 8;  // pin 14 on the 75HC595
int PIN_SCK = 9;  // pin 12 on the 75HC595
int PIN_RCK = 10; // pin 11 on the 75HC595

int i = 0;
int direction = 1; // 1 = L2R, -1 R2L

// shift register instance
MM74HC595 registers(PIN_SER, PIN_SCK, PIN_RCK, NUM_SHIFT_REGISTERS);

// module pins already initialzed
void setup() {;}               

void loop(){
 
 // reset all pins (set to LOW)
 registers.reset();
 
 // set pin(s) to high
 registers.set(i, true);
 
 // activate outputs
 registers.update();
 
 // check if we have to change direction
  if (i+1 == NUM_SHIFT_REGISTERS * 8) {
   direction = -1;
  } else if (i == 0) {
   direction = 1;
  }
  i += direction;

  delay(100);
}

Knight Rider with 74HC595 8 bit shift register

Please note, the next article «Finally a threesome» includes an arduino library for the 74HC595 (not for the 74HC594) and probably obsoletes this post.

---

/**
 * Board: Pro Mini 5V
 *
 *  $Id: test_74HC595.pde 293 2011-10-06 17:30:05Z wunderlins $
 */

int SER_Pin = 8;   //pin 15 on the 75HC595
int RCLK_Pin = 9;  //pin 12 on the 75HC595
int SRCLK_Pin = 10; //pin 10 on the 75HC595

//How many of the shift registers - change this
#define number_of_74hc595s 1 

#define numOfRegisterPins number_of_74hc595s * 8
boolean registers[numOfRegisterPins];

void setup(){
  pinMode(SER_Pin, OUTPUT);
  pinMode(RCLK_Pin, OUTPUT);
  pinMode(SRCLK_Pin, OUTPUT);

  //reset all register pins
  clearRegisters();
  writeRegisters();
}               

//set all register pins to LOW
void clearRegisters() {
  for(int i = numOfRegisterPins - 1; i >=  0; i--){
     registers[i] = LOW;
  }
} 

//Set and display registers
//Only call AFTER all values are set how you would like (slow otherwise)
int direction = 1; // 1 = L2R, -1 R2L
void writeRegisters(){

  digitalWrite(RCLK_Pin, LOW);

  for(int i = numOfRegisterPins - 1; i >=  0; i--){
    digitalWrite(SRCLK_Pin, LOW);

    int val = registers[i];

    digitalWrite(SER_Pin, val);
    digitalWrite(SRCLK_Pin, HIGH);

  }
  digitalWrite(RCLK_Pin, HIGH);

}

//set an individual pin HIGH or LOW
void setRegisterPin(int index, int value){
  registers[index] = value;
}

int i = 0;
void loop(){
 
 clearRegisters();
 
  setRegisterPin(i, HIGH);
  
  writeRegisters();  //MUST BE CALLED TO DISPLAY CHANGES
  //Only call once after the values are set how you need.
  
  if (i+1 == numOfRegisterPins) {
   direction = -1;
  } else if (i == 0) {
   direction = 1;
  }
  i += direction;

  delay(100);
} 

Code example is borrowed from here: http://bildr.org/2011/02/74hc595/