Accurate Arduino Clock

Check out the links above for our tutorials and wiring diagrams
These displays use SPI to communicate, 3 or 4 pins are required to
interface (RST is optional)
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!

Written by Limor Fried/Ladyada for Adafruit Industries.
MIT license, all text above must be included in any redistribution
****************************************************/

#include <Adafruit_GFX.h>
#include <Adafruit_HX8340B.h>

// if we're using fast hardware SPI on an '328 or '168 arduino such
// as an Uno, Duemilanove, Diecimila, etc then the MOSI and CLK
// pins are 'fixed' in hardware. If you'rere using 'bitbang' (slower)
// interfacing, you can change any of these pins as deired.
#define TFT_MOSI 11 // SDI
#define TFT_CLK 13 // SCL
#define TFT_CS 10 // CS
#define TFT_RESET 9 // RESET

// Color definitions
#define BLACK 0x0000
#define BLUE 0x001F
#define RED 0xF800
#define GREEN 0x07E0
#define CYAN 0x07FF
#define MAGENTA 0xF81F
#define YELLOW 0xFFE0
#define WHITE 0xFFFF

#include

// Option 1: use any pins but much slower
//Adafruit_HX8340B display(TFT_MOSI, TFT_CLK, TFT_RESET, TFT_CS);

// Option 2: must use the hardware SPI pins
// (for UNO thats sclk = 13 and sid = 11) and pin 10 must be
// an output. This is much faster - also required if you want
// to use the microSD card (see the image drawing example)
Adafruit_HX8340B display(TFT_RESET, TFT_CS);

//display
String appVersion = "Arduino PWM Clock v2";//"Arduino PWM Interrupt Clock"
int clockTextSize = 3;
int cyclesPerSecond = 974;

//pins
int clockInterrupt = 0; //interrupt 0 is pin 2 on UNO
int pwmOut = 6; //pin 6

//timekeeping
int seconds = 0;
int minutes = 0;
int hours = 0;
int masterClock = 0;//number of square waves

void setup(void) {
// clockInterrupt is our interrupt, clockCounter() function is called when invoked on a RISING clock edge
attachInterrupt(clockInterrupt, clockCounter, RISING);

//I always give enough time to restart if its locked
delay(2000);

//start serial communication for debugging
Serial.begin(9600);

analogReference(DEFAULT);//not sure if this is needed

display.begin();//starts the screen

display.fillScreen(BLACK);//wipe screen blank
display.setCursor(5,210);//bottom line of screen
display.print(appVersion);

Serial.print("writing to pin: ");
Serial.println(pwmOut);
analogWrite(pwmOut, 127); // this starts our PWM 'clock' with a 50% duty cycle//digital pin 10 for analogWrite pwm out
}

void loop() {
tftPrintTime();
serialPrintTime();
delay(800);
}

void clockCounter() // called by interrupt 0 (pin 2 on the UNO) receiving a rising clock edge PWM
{
masterClock ++; // with each clock rise add 1 to masterclock count
if(masterClock == cyclesPerSecond) // 974hz on pin 6, may be 490Hz if you use pin 9 or 10
{
seconds ++; // after one cycle add 1 second
masterClock = 0; //reset clock counter

if(seconds==60){
minutes++;
seconds = 0;//reset seconds counter

if(minutes==60){
hours++;
minutes = 0;
}
}
}
return;
}

void tftPrintTime() {
//display.fillScreen(BLACK);
display.fillRect(0, 0 , 170, 45, BLACK);

display.setCursor(0, 5);
display.setTextColor(BLUE);
display.setTextSize(clockTextSize);

if(hours<10){
display.print("0");
}
display.print(hours);
display.print(":");

if(minutes<10){
display.print("0");
}
display.print(minutes);
display.print(":");
if(seconds<10){
display.print("0");
}
display.println(seconds);
}

void serialPrintTime(){
if(hours<10){
Serial.print("0");
}
Serial.print(hours);
Serial.print(":");

if(minutes<10){
Serial.print("0");
}
Serial.print(minutes);
Serial.print(":");
if(seconds<10){
Serial.print("0");
}
Serial.println(seconds);