LED_binary_clock.c

// 2009 Kenneth Finnegan
// kennethfinnegan.blogspot.com
// http://kennethfinnegan.blogspot.com/2010/01/arduino-binary-clock.html

#include <Wire.h>

#define DS1307 B1101000
#define LEDDATA  7
#define LEDCLOCK  8
#define LEDLATCH  9
#define LEDAMPM  13
#define MINUTEBUTTON 2
#define HOURBUTTON  3

byte second=0, minute=0, hour=0;

void updatedisplay();
void updatetime();
byte DECTOBCD(byte val);
byte BCDTODEC(byte val);

void setup() {
  Wire.begin();
  pinMode(LEDDATA, OUTPUT);
  pinMode(LEDCLOCK, OUTPUT);
  pinMode(LEDLATCH, OUTPUT);
  pinMode(LEDAMPM, OUTPUT);
  digitalWrite(LEDLATCH, HIGH);
  
  pinMode(MINUTEBUTTON, INPUT);
  pinMode(HOURBUTTON, INPUT);
  digitalWrite(MINUTEBUTTON, HIGH); // activate pullup R
  digitalWrite(HOURBUTTON, HIGH); // activate pullup R
}

void loop() {
  updatedisplay();
  if (digitalRead(MINUTEBUTTON) == LOW) {
    minute = (minute+1) % 60;
    // Set seconds to zero so that the clock stop
    // flag gets upset on the DS1307. It's also nice
    // to have the seconds zero out to get the time
    // setting exact.
    second = 0;
    updatetime();
    updatedisplay();
    delay(300);
  }
  if (digitalRead(HOURBUTTON) == LOW) {
    hour = (hour + 1) % 24;
    updatetime();
    updatedisplay();
    delay(300);
  }
}

void updatedisplay() {

  Wire.beginTransmission(DS1307);
  Wire.send(0x00);
  Wire.endTransmission();
  Wire.requestFrom(DS1307, 3);
  second = BCDTODEC(Wire.receive() & 0x7f);
  minute = BCDTODEC(Wire.receive());
  hour   = BCDTODEC(Wire.receive() & 0x3f);
  
  byte temphour = hour % 12;
  if (temphour == 0) {
    // Not zero, not one, but 12. What the F, world?
    temphour = 12;
  }
  
  int leds = second + (minute<<6) + (temphour<<12);
  digitalWrite(LEDLATCH, LOW); // lock display before updating
  // Arduino gives us a nice shiftOut function for shift registers
  shiftOut(LEDDATA, LEDCLOCK, MSBFIRST, highByte(leds));
  shiftOut(LEDDATA, LEDCLOCK, MSBFIRST, lowByte(leds));
  digitalWrite(LEDLATCH, HIGH);
  digitalWrite(LEDAMPM, hour/12);
}

void updatetime() {
  // Send the time back to the DS1307 when the user
  // presses a button to advance the hours or minutes
  Wire.beginTransmission(DS1307);
  Wire.send(0x00);
  Wire.send(DECTOBCD(second));
  Wire.send(DECTOBCD(minute));
  Wire.send(DECTOBCD(hour));
  Wire.endTransmission();
}

byte DECTOBCD(byte val) {
  return ((val/10)<<4) + (val%10);
}
byte BCDTODEC(byte val) {
  return (val>>4) * 10 + (val & 0xf);
}