simpleclock/simpleclock.ino

/*
 * 7 Segment 4 Digits clock with digit point separator
 *
 * It uses display module with common anode and DS1307 RTC module to enhance
 * time keeping ability of Atmega 328p based Arduino Nano microcontroller and
 * 2 buttons for adjusting time.
 */

/* DS1307 lib by FrankieChu for Seeed RTC module, in my case
 * Grove___RTC_DS1307-1.0.0.zip */
#include <DS1307.h>
#include <SevSeg.h>

DS1307 clock;
SevSeg Display;

/* push button stuff */
const long initial_delay = 600;   // wait a bit before spin numbers
const long adjust_interval = 200; // delay between consecutive number increments
const long bounce_delay = 20;     // contact bounce compensation
const int hrs_btn = A0;           // put hour adjusting button on A0 lane
const int min_btn = A1;           // put minute adjusting button on A1 lane
volatile bool btn_pushed = false; // is button pushed?
unsigned long previousPushTimer = 0;

/* dot blinking stuff */
volatile bool dot = true;

/* time inaccuracy compensation flag */
volatile bool compflag1 = true;
volatile bool compflag2 = false;
const uint8_t timeSkew = 8;          // assume that clock runs faster than should
volatile bool timeSkewEven = false;  // comp. 1 additional second per 2 days

/* time vars */
volatile uint8_t mysecond;
volatile uint8_t myminute;
volatile uint8_t myhour;

/* rtc sync flag */
volatile bool rtcsync = true;

void setup()
{
	// setup display
	byte hardwareConfig = COMMON_ANODE;
	byte numDigits = 4;
	byte digitPins[] = {9, 10, 11, 12};
	byte segmentPins[] = {2, 3, 4, 5, 6, 7, 8, 13};
	bool resistorsOnSegments = true; // 8 resistors, 330 Ohms each
	bool updateWithDelays = false;   // Default. Recommended

	/* without it there is visual bug at 0 o'clock, and in current version
	 * of SevSeg' setChars() does not dots at all */
	bool leadingZeros = false;

	Display.begin(hardwareConfig, numDigits, digitPins, segmentPins,
	              resistorsOnSegments, updateWithDelays, leadingZeros);
	Display.setBrightness(100);

	// setup clock
	clock.begin();

	// if rtc returns incorrect time, reset it to some default value
	clock.getTime();

	if ((clock.hour > 23) || (clock.minute > 59)) {
		clock.fillByYMD(2019, 2, 23); // 23 Feb 2019
		clock.fillByHMS(15, 52, 30);  // 15:52:30"
		clock.fillDayOfWeek(SAT);     // Saturday
		clock.setTime();              // put date to rtc
	}

	// setup control buttons
	pinMode(hrs_btn, INPUT_PULLUP);
	pinMode(min_btn, INPUT_PULLUP);
	
/* Timer stuff
 * timer0 being used in millis() micros() delay() etc, it has 8 bit resolution
 * timer2 being used in analogWrite() tone() notone(), it has 8 bit resolution
 * timer1 being used in servo lib has 16 bit resolution
 * We'll use timer1, since we have no mechanical parts and don't need servo lib
 */
	// initialize timer1
	noInterrupts();           // disable all interrupts
	TCCR1A = 0;
	TCCR1B = 0;

	TCNT1 = 34286;            // preload timer 65536-16MHz/256/2Hz
	TCCR1B |= (1 << CS12);    // 256 prescaler 
	TIMSK1 |= (1 << TOIE1);   // enable timer overflow interrupt
	interrupts();             // enable all interrupts
}

ISR(TIMER1_OVF_vect)
{
/* Feed clock twice per second */
	TCNT1 = 34286;            // preload timer
	// do not read rtc if time beng adjusted by buttons
	(btn_pushed) ? rtcsync : rtcsync = true;

/* Also switch dot */
	if (dot)
		dot = false;
	else
		dot = true;

/* time compensation magic */
	if ((myhour == 21) and (myminute == 21) and (mysecond == 21)
	    and (compflag2)) {
		compflag1 = true;
		(timeSkewEven) ? timeSkewEven = false : timeSkewEven;
	}

	if ((myhour == 21) and (myminute == 21) and (mysecond == 23)) {
		compflag1 = false;
		compflag2 = true;
	}
}

void loop()
{
	unsigned long currentMillis = millis();

/*
 * Let's implement time compenstion for individual rtc module time
 * charachteristics. In in my case quartz resonator as inaccurate as
 * about +8.5 seconds per 24 hours
 */
	if (compflag1 && compflag2) {
		if (timeSkewEven) {
			clock.fillByHMS(myhour, myminute, (mysecond - timeSkew - 1));
		} else {
			clock.fillByHMS(myhour, myminute, (mysecond - timeSkew));
		}

		clock.setTime();
		compflag2 = false;
	}

	if (rtcsync) {
		clock.getTime();
		mysecond = clock.second;
		myminute = clock.minute;
		myhour = clock.hour;
		updateTimeStr(myhour, myminute);
		rtcsync = false;
	}

	// push button magic
	if ((!btn_pushed) and
	    ((digitalRead(hrs_btn) == LOW) or (digitalRead(min_btn) == LOW))) {
		if (currentMillis - previousPushTimer >= initial_delay) {
			previousPushTimer = currentMillis;
			btn_pushed = true;
		}
	}

	if (btn_pushed and
	    (digitalRead(hrs_btn) != LOW) and (digitalRead(min_btn) != LOW)) {
		// compensate possible contact bounce with delay
		if (currentMillis - previousPushTimer >= bounce_delay) {
			btn_pushed = false;
		}
	}

	if (btn_pushed) {
		if (currentMillis - previousPushTimer >= adjust_interval) {
			previousPushTimer = currentMillis;

			if (digitalRead(hrs_btn) == LOW) {
				myhour++;
				(myhour > 23) ? myhour = 0 : myhour;
				clock.fillByHMS(myhour, myminute, 0);
				clock.setTime();
			}

			if (digitalRead(min_btn) == LOW) {
				myminute++;
				(myminute > 59) ? myminute = 0 : myminute;
				clock.fillByHMS(myhour, myminute, 0);
				clock.setTime();
			}
		}

		updateTimeStr(myhour, myminute);
	}

	Display.refreshDisplay();
}

void updateTimeStr(uint8_t h, uint8_t m)
{
	if (dot) {
		char str[5];
		sprintf(str, "%2d.%02d", h, m);
		Display.setChars(str);
	} else {
		char str[4];
		sprintf(str, "%2d%02d", h, m);
		Display.setChars(str);
	}
}

/* vim: set filetype=cpp: */