Update README.md

* Poll RTC by trigger, set via ISR
* Change blink state by trigger, set via ISR
* Set time compensation trigger in ISR
* Refresh clock by timer
* Re-calculate displayed time only ater rtcsync or when time adjusted by buttons
* Simplify draw algo

.gitignore

@@ -0,0 +1,6 @@
+.vscode/*
+*.swp
+*.bak
+*.old
+*.orig
+*.clang-format

README.md

@@ -4,13 +4,32 @@
 
 ### Component base is very simple:
 
-* Arduino NANO v3 chinese replica
-* 7 segment 4 digit LED indicator with common anode, FYQ-5641BG-21
+* Arduino NANO v3 chinese replica (on Atmega-168 chip)
+* 7 segment 4 digit LED indicator with common anode, FYQ-5641BD-21 (red LEDs)
 * 8 resistors that limiting current on LED segments, 330 Ohms, 0.25 watts
-* RTC Module GEEGROW with DS1307 chip
+* RTC Module GEEGROW with DS1307 chip (very basic, only RTC chip, quartz resonator, button battery, no additional memory chip)
 * 5x7 cm single side prototyping board
 * usb phone charger as power supply
 * 2 push buttons
 * 1 on/off switch
 * Gainta G521G enclosure (92x66.5x28мм)
 * 5m power cord
+
+### Optionally you may need:
+
+* Capasitor with well capacity if your charger has small capasitor on output
+* Fuse, to protect your device
+* DC/DC transformer if you have power supply that gives more than 5 volts or less than 4.5 volts (this will give additional surge protection if your power supply dies, this can happen after 3-5 years of uninterrupted work)
+
+### Additional Notes:
+
+My RTC module is not very accurate due to bad quartz chrystal calibration, looks like it is not exactly 32768 Hz and clock runs faster than it should be, giving about 5-8 seconds runaway per day. So i have to implement time correction in software (temperature changes during day/month/year is not very big - about 10 degrees Celsius, so we can use software compensation without thermal compensation).
+
+This project split into 2 branches:
+
+* **default** that contains generic clock without any additional elements
+* **photoresistor** that contains additional hardware - photocell bridge - and software algorithm that compensates ambient light sensed by photocell basing on LED display charachteristics.
+
+### Stable tags for branches:
+v1.6 - default
+v1.7 - photoresistor

simpleclock.ino

@@ -1,53 +1,44 @@
 /*
  * 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
+ * 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.
  */
 
-/* This software distributed under BSD 2 Clause License
-
-Copyright (c) Sergei Fedosoff, All rights reserved.
-
-Redistribution and use in source and binary forms, with or without modification,
-are permitted provided that the following conditions are met:
-
-Redistributions of source code must retain the above copyright notice, this list
-of conditions and the following disclaimer. Redistributions in binary form must
-reproduce the above copyright notice, this list of conditions and the following
-disclaimer in the documentation and/or other materials provided with the
-distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
-CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
-PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
-CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
-OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
-SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
-INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
-CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
-IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
-OF SUCH DAMAGE.
-*/
-
-#include <SevSeg.h>
-#include <Wire.h>
-#include <TimeLib.h>
-// DS1307 lib by FrankieChu for Seeed RTC module
+/* 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;
 
-unsigned long currentMillis;
-unsigned long previousMillis = 0;
-const long interval = 500;
-const int hrs_btn = A0;
-const int min_btn = A1;
-bool dot = true;
-uint8_t minutes;
-uint8_t hours;
+/* 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()
 {
@@ -58,13 +49,14 @@ void setup()
 	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 = true;          
+
+	/* 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(90);
+	Display.setBrightness(100);
 
 	// setup clock
 	clock.begin();
@@ -72,10 +64,9 @@ void setup()
 	// 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 2013
-		clock.fillByHMS(15,52,30);   // 15:52 30"
+	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
 	}
@@ -83,55 +74,132 @@ void setup()
 	// 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();
 
-	if (currentMillis - previousMillis >= interval)
-	{
-		previousMillis = currentMillis;
-
-		if (dot == false)
-		{
-			dot = true;
-
-			if (digitalRead(hrs_btn) == LOW)
-			{
-				clock.getTime();
-				hours = clock.hour + 1;
-				(hours > 23)? hours = 0: hours;
-				clock.fillByHMS(hours, clock.minute, 0);
-				clock.setTime();
-			}
-
-			if (digitalRead(min_btn) == LOW)
-			{
-				clock.getTime();
-				minutes = clock.minute + 1;
-				(minutes > 59)? minutes = 0: minutes;
-				clock.fillByHMS(clock.hour, minutes, 0);
-				clock.setTime();
-			}
-		}
-		else
-		{
-			dot = false;
-		}
-	}
-
-	clock.getTime();
-
-	// make blinking dot
-	if (dot == true) {
-		Display.setNumber((clock.hour * 100 + clock.minute), 2);
+/*
+ * 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 {
-		Display.setNumber((clock.hour * 100 + clock.minute));
+			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: */