Count Down Clock

Just a simple Arduino project for the last day of the year: a Count Down Clock showing the time left until New Year.

Time is derived from a DS1307 RTC module and displayed on a 8×32 LED Matrix Module. At 23:00 hours, the initial HH:MM format will switch to MM:SS.

/*  When started on 31 December, shows the time left until New Year on an 8x32 LED matrix. Uses a DS1307 or DS3231 RTC module)
    Matrix:
      pin 12 is connected to the Din 
      pin 11 is connected to the CLK 
      pin 10 is connected to CS
    RTC Module:
      SDA to A4
      SCL to A5
    VCC of both modules to 5 volt
*/
#include "LedControl.h"
#include <Wire.h>
const int DS1307 = 0x68; // Address of DS1307 see data sheets

static int nMods = 4;
LedControl lc=LedControl(12,11,10,nMods);

int j, k, m;
int c[4];

// (moduleindex,kolomindex} van rechterkolom voor de vier cijferposities
int rpos[4][2] = {
                          {0,1},  // Hh
                          {1,3},  // hH
                          {2,1},  // Mm
                          {3,3}   // mM
                        };

// elk cijfer (1-ste index) beschreven van links naar rechts (5 kolommen)
static int digits[10][5] = {
                              { 0x7c, 0xa2, 0x92, 0x8a, 0x7c},  // 0
                              { 0x00, 0x84, 0xfe, 0x80, 0x00},  // 1
                              { 0xc4, 0xa2, 0x92, 0x92, 0x8c},  // 2
                              { 0x44, 0x82, 0x92, 0x92, 0x6c},  // 3
                              { 0x30, 0x28, 0x24, 0xfe, 0x20},  // 4
                              { 0x4e, 0x8a, 0x8a, 0x8a, 0x72},  // 5
                              { 0x78, 0x94, 0x92, 0x92, 0x60},  // 6
                              { 0x02, 0xe2, 0x12, 0x0a, 0x06},  // 7
                              { 0x6c, 0x92, 0x92, 0x92, 0x6c},  // 8
                              { 0x0c, 0x92, 0x92, 0x52, 0x3c}   // 9
                           };
                        
 // Initializes all values: 
 byte second = 0;
 byte minute = 0;
 byte hour = 0;
 byte second2 = 0;
 byte minute2 = 0;
 byte hour2 = 0;
 byte weekday = 0;
 byte monthday = 0;
 byte month = 0;
 byte year = 0;

 void setup() {
   Wire.begin();
   delay(2000); // This delay allows the MCU to read the current date and time.
   for (j=0;j<nMods;j++) {
        lc.shutdown(j,false);
        lc.setIntensity(j,1);
        lc.clearDisplay(j);
   }
 }

  void loop() {
  readTime();

  if (hour==0 && minute==0 && second==0) { // Flashing New Year in endless loop
    int y[4];
    y[0] = 2;
    y[1] = 0;
    y[3] = year%10;
    y[2] = (year-y[3])/10;
    while(1) {  
      for(m=0;m<4;m++) {
        k=0;
        for (j=m+4;j>=m;j--) {
          lc.setColumn(m,j,digits[y[m]][k]);
          k++;
        }
      }
      delay(500);
      for (j=0;j<4;j++) {
        lc.clearDisplay(j);
      }
      delay(500);
    }
 
  }

  // Not there yet: calculate the hours, minutes and seconds until midnight
/* 
Just for the challenge, I decided not to use any 'if...then' loops for this.
I figured out how it can be done with using abs(), max() and min() instead.
*/ 
  second2=(60-second)%60;
  minute2=(60-minute-abs(min(0,-second))/max(abs(-second),1))%60;
  hour2=(24-hour-abs(min(0,-minute-abs(min(0,-second))/max(abs(-second),1)))/max(abs(-minute-abs(min(0,-second))/max(abs(-second),1)),1))%24;

  // display mode selection (there are only 4 digits)
  if (hour != 23) {             // Display HH:MM
      c[1] = hour2%10;
      c[0]= (hour2-c[1])/10;
      c[3] = minute2%10;
      c[2] =(minute2-c[3])/10;
  } else {                      // Display MM:SS
      c[1] = minute2%10;
      c[0]= (minute2-c[1])/10;
      c[3] = second2%10;
      c[2] =(second2-c[3])/10;
  }

      for (int p=3;p>=0;p--) {
        m = rpos[p][0]; //moduleindex rechterkolom van het cijfer op positie p (zero offset)
        k = rpos[p][1]; //kolomindex rechterkolom van het cijfer op positie p (zero offset)
        for (j=4;j>=0;j--) {
          lc.setColumn(m,k,digits[c[p]][j]);
          k++;
          if (k>7) {
            k=0;
            m--;
          }
        }
      }

      // scheidingsteken
      lc.setColumn(1,0,0x44);
  
  delay(20);
 }
 
 byte decToBcd(byte val) {
   return ((val/10*16) + (val%10));
 }
 byte bcdToDec(byte val) {
   return ((val/16*10) + (val%16));
 }

  void readTime() {
   Wire.beginTransmission(DS1307);
   Wire.write(byte(0));
   Wire.endTransmission();
   Wire.requestFrom(DS1307, 7);
   second = bcdToDec(Wire.read());
   minute = bcdToDec(Wire.read());
   hour = bcdToDec(Wire.read());
   weekday = bcdToDec(Wire.read());
   monthday = bcdToDec(Wire.read());
   month = bcdToDec(Wire.read());
   year = bcdToDec(Wire.read());
 }

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/* When started on 31 December, shows the time left until New Year on an 8x32 LED matrix. Uses a DS1307 or DS3231 RTC module)

Matrix:

pin 12 is connected to the Din

pin 11 is connected to the CLK

pin 10 is connected to CS

RTC Module:

SDA to A4

SCL to A5

VCC of both modules to 5 volt

#include "LedControl.h"

#include <Wire.h>

const int DS1307 = 0x68; // Address of DS1307 see data sheets

static int nMods = 4;

LedControl lc=LedControl(12,11,10,nMods);

int j, k, m;

int c[4];

// (moduleindex,kolomindex} van rechterkolom voor de vier cijferposities

int rpos[4][2] = {

{0,1}, // Hh

{1,3}, // hH

{2,1}, // Mm

{3,3} // mM

};

// elk cijfer (1-ste index) beschreven van links naar rechts (5 kolommen)

static int digits[10][5] = {

{ 0x7c, 0xa2, 0x92, 0x8a, 0x7c}, // 0

{ 0x00, 0x84, 0xfe, 0x80, 0x00}, // 1

{ 0xc4, 0xa2, 0x92, 0x92, 0x8c}, // 2

{ 0x44, 0x82, 0x92, 0x92, 0x6c}, // 3

{ 0x30, 0x28, 0x24, 0xfe, 0x20}, // 4

{ 0x4e, 0x8a, 0x8a, 0x8a, 0x72}, // 5

{ 0x78, 0x94, 0x92, 0x92, 0x60}, // 6

{ 0x02, 0xe2, 0x12, 0x0a, 0x06}, // 7

{ 0x6c, 0x92, 0x92, 0x92, 0x6c}, // 8

{ 0x0c, 0x92, 0x92, 0x52, 0x3c} // 9

};

// Initializes all values:

byte second = 0;

byte minute = 0;

byte hour = 0;

byte second2 = 0;

byte minute2 = 0;

byte hour2 = 0;

byte weekday = 0;

byte monthday = 0;

byte month = 0;

byte year = 0;

void setup() {

Wire.begin();

delay(2000); // This delay allows the MCU to read the current date and time.

for (j=0;j<nMods;j++) {

lc.shutdown(j,false);

lc.setIntensity(j,1);

lc.clearDisplay(j);

}

void loop() {

readTime();

if (hour==0 && minute==0 && second==0) { // Flashing New Year in endless loop

int y[4];

y[0] = 2;

y[1] = 0;

y[3] = year%10;

y[2] = (year-y[3])/10;

while(1) {

for(m=0;m<4;m++) {

k=0;

for (j=m+4;j>=m;j--) {

lc.setColumn(m,j,digits[y[m]][k]);

k++;

}

delay(500);

for (j=0;j<4;j++) {

lc.clearDisplay(j);

}

delay(500);

}

// Not there yet: calculate the hours, minutes and seconds until midnight

Just for the challenge, I decided not to use any 'if...then' loops for this.

I figured out how it can be done with using abs(), max() and min() instead.

second2=(60-second)%60;

minute2=(60-minute-abs(min(0,-second))/max(abs(-second),1))%60;

hour2=(24-hour-abs(min(0,-minute-abs(min(0,-second))/max(abs(-second),1)))/max(abs(-minute-abs(min(0,-second))/max(abs(-second),1)),1))%24;

// display mode selection (there are only 4 digits)

if (hour != 23) { // Display HH:MM

c[1] = hour2%10;

c[0]= (hour2-c[1])/10;

c[3] = minute2%10;

c[2] =(minute2-c[3])/10;

} else { // Display MM:SS

c[1] = minute2%10;

c[0]= (minute2-c[1])/10;

c[3] = second2%10;

c[2] =(second2-c[3])/10;

}

for (int p=3;p>=0;p--) {

m = rpos[p][0]; //moduleindex rechterkolom van het cijfer op positie p (zero offset)

k = rpos[p][1]; //kolomindex rechterkolom van het cijfer op positie p (zero offset)

for (j=4;j>=0;j--) {

lc.setColumn(m,k,digits[c[p]][j]);

k++;

if (k>7) {

k=0;

m--;

}

// scheidingsteken

lc.setColumn(1,0,0x44);

delay(20);

}

byte decToBcd(byte val) {

return ((val/10*16) + (val%10));

}

byte bcdToDec(byte val) {

return ((val/16*10) + (val%16));

}

void readTime() {

Wire.beginTransmission(DS1307);

Wire.write(byte(0));

Wire.endTransmission();

Wire.requestFrom(DS1307, 7);

second = bcdToDec(Wire.read());

minute = bcdToDec(Wire.read());

hour = bcdToDec(Wire.read());

weekday = bcdToDec(Wire.read());

monthday = bcdToDec(Wire.read());

month = bcdToDec(Wire.read());

year = bcdToDec(Wire.read());

}