LucidTronix 7 Segment LED and 74HC595 shift register Tutorial

// LucidTronix 7 Segment LED and 74HC595 shift register Tutorial

http://www.lucidtronix.com/tutorials/41

//! +---+-------+-------------------------------+
//! |No.|PinName|Pin Description                |
//! |---|-------|-------------------------------|
//! | 1 |   E   |Digital Pin input              |
//! | 2 |   D   |Digital Pin input              |
//! | 3 |  COM  |Commont pin input(VCC or GND)  |
//! | 4 |   C   |Digital Pin input              |
//! | 5 |  DP   |Digital Pin input              |
//! | 6 |   B   |Digital Pin input              |
//! | 7 |   A   |Digital Pin input              |
//! | 8 |  COM  |Commont pin input(VCC or GND)  |
//! | 9 |   F   |Digital Pin input              |
//! |10 |   G   |Digital Pin input              |
//! +---+-------+-------------------------------+

int dataPin = 2;
int latchPin = 3;
int clockPin = 4;

byte dec_digits[] = {0b11000000,0b11111001,0b10100100,0b10110000,
0b10011001,0b10010010,0b10000011,0b11111000,0b10000000,0b10011000 };

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

void loop() 
{
  for (int numberToDisplay = 0; numberToDisplay < 10; 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, MSBFIRST, dec_digits[numberToDisplay]); 

    //take the latch pin high so the LEDs will light up:
    digitalWrite(latchPin, HIGH);

    // pause before next value:
    delay(300);
  }
}

.END



Arduino shiftOut() function

http://arduino.cc/en/Reference/ShiftOut

Description

Shifts out a byte of data one bit at a time. Starts from either the most (i.e. the leftmost) or least (rightmost) significant bit. Each bit is written in turn to a data pin, after which a clock pin is pulsed (taken high, then low) to indicate that the bit is available.

Note: if you're interfacing with a device that's clocked by rising edges, you'll need to make sure that the clock pin is low before the call to shiftOut(), e.g. with a call to digitalWrite(clockPin, LOW).

This is a software implementation; see also the SPI library, which provides a hardware implementation that is faster but works only on specific pins.

Syntax

shiftOut(dataPin, clockPin, bitOrder, value)

Parameters

dataPin: the pin on which to output each bit (int)

clockPin: the pin to toggle once the dataPin has been set to the correct value (int)

bitOrder: which order to shift out the bits; either MSBFIRST or LSBFIRST.
(Most Significant Bit First, or, Least Significant Bit First)

value: the data to shift out. (byte)

Returns

None

Note

The dataPin and clockPin must already be configured as outputs by a call to pinMode().

shiftOut is currently written to output 1 byte (8 bits) so it requires a two step operation to output values larger than 255.

...

Example

For accompanying circuit, see the tutorial on controlling a 74HC595 shift register.

//**************************************************************//
//  Name    : shiftOutCode, Hello World                         //
//  Author  : Carlyn Maw,Tom Igoe                               //
//  Date    : 25 Oct, 2006                                      //
//  Version : 1.0                                               //
//  Notes   : Code for using a 74HC595 Shift Register           //
//          : to count from 0 to 255                            //
//****************************************************************

//Pin connected to ST_CP of 74HC595
int latchPin = 8;
//Pin connected to SH_CP of 74HC595
int clockPin = 12;
////Pin connected to DS of 74HC595
int dataPin = 11;

void setup() {
  //set pins to output because they are addressed in the main loop
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
}

void loop() {
  //count up routine
  for (int j = 0; j < 256; j++) {
    //ground latchPin and hold low for as long as you are transmitting
    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, LSBFIRST, j);   
    //return the latch pin high to signal chip that it 
    //no longer needs to listen for information
    digitalWrite(latchPin, HIGH);
    delay(1000);
  }
} 


.END2