Intel Edison C++ 74HC595 Shift Register Example Code

/*     ---------------------------------------------------------

*     |  Intel Edison C++ Example Code                         |

*     |  CIRC-05 .: 8 More LEDs :. (74HC595 Shift Register)    |

*     ---------------------------------------------------------

*

* We have already controlled 8 LEDs however this does it in a slightly

* different manner. Rather than using 8 pins we will use just three

* and an additional chip.

*

*/

#include <stdio.h>

#include <signal.h>

#include <unistd.h>

#include <mraa/gpio.h>

//Pin Definitions

//The 74HC595 uses a serial communication

//link which has three pins

#define DIR_CLOCK 4

#define DIR_EN        7

#define DIR_SER   8

#define DIR_LATCH 12

#define LOW  0

#define HIGH 1

#define MSBFIRST 1

#define LSBFIRST 0

using namespace std;

sig_atomic_t volatile isrunning = 1;

void sig_handler(int signum);

void shiftOut(mraa_gpio_context dataPin, mraa_gpio_context clockPin, uint8_t bitOrder, uint8_t val);

//Used for single LED manipulation

int ledState = 0;

const int ON = HIGH;

const int OFF = LOW;

int main()

{

       signal(SIGINT, &sig_handler);

       mraa_init();

       mraa_gpio_context data_pin;

       mraa_gpio_context clock_pin;

       mraa_gpio_context latch_pin;

       mraa_gpio_context enable_pin;

       data_pin = mraa_gpio_init(DIR_SER);

       clock_pin= mraa_gpio_init(DIR_CLOCK);

       latch_pin= mraa_gpio_init(DIR_LATCH);

       enable_pin = mraa_gpio_init(DIR_EN);

       mraa_gpio_dir(data_pin,  MRAA_GPIO_OUT);

       mraa_gpio_dir(clock_pin, MRAA_GPIO_OUT);

       mraa_gpio_dir(latch_pin, MRAA_GPIO_OUT);

       mraa_gpio_dir(enable_pin, MRAA_GPIO_OUT);

       while (isrunning)

       {

             int delayTime = 100000; //the number of microseconds to delay between LED updates

             for (int i = 0; i < 256; i++)

             {

                    mraa_gpio_write(latch_pin, LOW);     //Pulls the chips latch low  

                    shiftOut(data_pin, clock_pin, MSBFIRST, i); //Shifts out the 8 bits to the shift register

                    mraa_gpio_write(latch_pin, HIGH); //Pulls the latch high displaying the data

                    usleep(delayTime);

                    printf("%d\n",i);

             }

       }

       return MRAA_SUCCESS;

}

void sig_handler(int signum)

{     

       if (signum == SIGINT) isrunning = 0;

}

void shiftOut(mraa_gpio_context dataPin,mraa_gpio_context clockPin, uint8_t bitOrder,uint8_tval)

{

       uint8_t i;

       for (i = 0; i < 8; i++) {

             if (bitOrder == LSBFIRST)

                    mraa_gpio_write(dataPin, !!(val & (1 << i)));

             else

                    mraa_gpio_write(dataPin, !!(val & (1 << (7 - i))));

             mraa_gpio_write(clockPin, HIGH);

             mraa_gpio_write(clockPin, LOW);

       }

}