Update display text only by interrupt or on button press

* Re-calculate displayed time only ater rtcsync or when time adjusted by
  buttons

.gitignore

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

.hgignore

@@ -1,6 +0,0 @@
-^\.vscode
-\.swp$
-\.bak$
-\.old$
-\.orig$
-\.clang-format

.hgtags

@@ -1,3 +0,0 @@
-ee4999ebdd2d1b54512facafdd03c8a530ea4bfa v1.0
-1167bd4b622768ed17e116a4cbac3db90031e6f8 v1.1
-109112211e454e608911949914eaa2722fbfed7d v1.2

simpleclock.ino

@@ -6,65 +6,49 @@
  * 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 listof 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 POSSIBILITYOF SUCH DAMAGE.
- */
-
 /* DS1307 lib by FrankieChu for Seeed RTC module, in my case
  * Grove___RTC_DS1307-1.0.0.zip */
 #include <DS1307.h>
 #include <SevSeg.h>
 
+#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
+#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
+
 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 increnents
+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
-bool btn_pushed = false;          // is button pushed?
-unsigned long currentPushTimer;
+volatile bool btn_pushed = false; // is button pushed?
 unsigned long previousPushTimer = 0;
-uint8_t minutes;
-uint8_t hours;
 
 /* dot blinking stuff */
-unsigned long currentMillis;
-unsigned long previousMillis = 0;
-const long interval = 500;
-bool dot = true;
+volatile bool dot = true;
 
 /* time inaccuracy compensation flag */
-uint8_t compflag = 0;
-const uint8_t timeSkew = 6; // assume that clock runs faster than should
+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
 
 /* ambient light compensation aka night mode */
 const int photoPin = A2;
+volatile bool measureAmbLight = true;
+unsigned int ambLight = 0;
+unsigned long previousLightTimer = 0;
+const long refresh_interval = 40;    // refresh rate 25Hz
+
+/* time vars */
+volatile uint8_t mysecond;
+volatile uint8_t myminute;
+volatile uint8_t myhour;
+
+/* rtc sync flag */
+volatile bool rtcsync = true;
 
 void setup()
 {
@@ -74,19 +58,19 @@ void setup()
 	byte digitPins[] = {9, 10, 11, 12};
 	byte segmentPins[] = {2, 3, 4, 5, 6, 7, 8, 13};
 	bool resistorsOnSegments = true; // 8 resistors, 330 Ohms each
-        /* updateWithDelays defaults to false and it is recommended value,
-	 * but i was unable to make my display to change brightness with
+	/* updateWithDelays defaults to false and it is recommended value,
+	 * but i was unable to make my display to change brightness notably with
 	 * recommended value, so i have to use updateWithDelays=true,
 	 * in this case brightness gets changed.
 	 */
-	bool updateWithDelays = true;   // Default. Recommended
+	bool updateWithDelays = 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);
+	              resistorsOnSegments, updateWithDelays, leadingZeros);
 	Display.setBrightness(100);
 
 	// setup clock
@@ -106,130 +90,202 @@ void setup()
 	pinMode(hrs_btn, INPUT_PULLUP);
 	pinMode(min_btn, INPUT_PULLUP);
 
-	// setup brigtness sensor
+/* 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
+
+/* increase sampling rate of analogRead()
+ * by setting an ADC prescale from 128 to 16, so it takes less time to read
+ * sensor
+ */
+	sbi(ADCSRA, ADPS2);
+	cbi(ADCSRA, ADPS1);
+	cbi(ADCSRA, ADPS0);
+
+	// setup ambient brigtness sensor
 	pinMode(photoPin, INPUT);
+	ambLight = analogRead(photoPin);
+}
+
+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()
 {
-	currentMillis = millis();
-	currentPushTimer = currentMillis;
-	char str[4];
-	float d;
-	unsigned int ambLight = analogRead(photoPin);
+	unsigned long currentMillis = millis();
 
-	clock.getTime();
+/*
+ * 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 (currentPushTimer - previousPushTimer >= initial_delay) {
-			previousPushTimer = currentPushTimer;
+	    ((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)) {
+	    (digitalRead(hrs_btn) != LOW) and (digitalRead(min_btn) != LOW)) {
 		// compensate possible contact bounce with delay
-		if (currentPushTimer - previousPushTimer >= bounce_delay) {
+		if (currentMillis - previousPushTimer >= bounce_delay) {
 			btn_pushed = false;
 		}
 	}
 
 	if (btn_pushed) {
-		if (currentPushTimer - previousPushTimer >= adjust_interval) {
-			previousPushTimer = currentPushTimer;
+		if (currentMillis - previousPushTimer >= adjust_interval) {
+			previousPushTimer = currentMillis;
 
 			if (digitalRead(hrs_btn) == LOW) {
-				hours = clock.hour + 1;
-				(hours > 23) ? hours = 0 : hours;
-				clock.fillByHMS(hours, clock.minute, 0);
+				myhour++;
+				(myhour > 23) ? myhour = 0 : myhour;
+				clock.fillByHMS(myhour, myminute, 0);
 				clock.setTime();
 			}
 
 			if (digitalRead(min_btn) == LOW) {
-				minutes = clock.minute + 1;
-				(minutes > 59) ? minutes = 0 : minutes;
-				clock.fillByHMS(clock.hour, minutes, 0);
+				myminute++;
+				(myminute > 59) ? myminute = 0 : myminute;
+				clock.fillByHMS(myhour, myminute, 0);
 				clock.setTime();
 			}
 		}
+
+		updateTimeStr(myhour, myminute);
 	}
 
-	if (currentMillis - previousMillis >= interval) {
-		previousMillis = currentMillis;
+	if ((currentMillis - previousLightTimer >= refresh_interval) or
+	    (previousLightTimer > currentMillis)) { // millis() reset every ~49 days
+		previousLightTimer = currentMillis;
+		ambLight = analogRead(photoPin);
 
-		if (dot)
-			dot = false;
-		else
-			dot = true;
-	}
-
-	/*
-	 * Let's implement time compenstion for individual rtc module time
-	 * charachteristics. In in my case quartz resonator as inaccurate as
-	 * +/- about 5-8 seconds per 24 hours, maybe its require more EMI
-	 * shielding?
-	 */
-
-	if ((clock.hour == 21) and (clock.minute == 21) and
-            (clock.second == 21) and (compflag == 0)) {
-		clock.fillByHMS(clock.hour, clock.minute, (clock.second - timeSkew));
-		clock.setTime();
-		compflag = 1;
-	}
-
-	if ((clock.hour == 21) and (clock.minute == 21) and
-            (clock.second == 23) and (compflag == 1)) {
-		compflag = 0;
-	}
-
-	// make blinking dot
-	if (clock.hour > 0) {
-		if (dot) {
-			Display.setNumber((clock.hour * 100 + clock.minute), 2);
-		} else {
-			Display.setNumber((clock.hour * 100 + clock.minute));
+/* Ambient light compensation
+ * ambLight can be in range of 0..1023, if it 910+, it has point to use
+ * fullbright.
+ * Use table comparsion (not function of ambLight) because of non-linear
+ * charachteristics of led indicator, that cannot be described via simple
+ * formula.
+ */
+		if (ambLight >= 910) {
+			Display.setBrightness(100);
+		} else if ((ambLight < 900) and (ambLight >= 860)) {
+			Display.setBrightness(75);
+		} else if ((ambLight < 850) and (ambLight >= 810)) { 
+			Display.setBrightness(45);
+		} else if ((ambLight < 800) and (ambLight >= 760)) {
+			Display.setBrightness(25);
+		} else if ((ambLight < 750) and (ambLight >= 710)) {
+			Display.setBrightness(18);
+		} else if ((ambLight < 700) and (ambLight >= 660)) {
+			Display.setBrightness(12);
+		} else if ((ambLight < 650) and (ambLight >= 610)) {
+			Display.setBrightness(10);
+		} else if ((ambLight < 600) and (ambLight >= 560)) {
+			Display.setBrightness(7);
+		} else if ((ambLight < 550) and (ambLight >= 410)) {
+			Display.setBrightness(4);
+		} else if ((ambLight < 400) and (ambLight >= 360)) {
+			Display.setBrightness(0);
+		} else if ((ambLight < 350) and (ambLight >= 310)) {
+			Display.setBrightness(-3);
+		} else if ((ambLight < 300) and (ambLight >= 260)) {
+			Display.setBrightness(-5);
+		} else if ((ambLight < 250) and (ambLight >= 210)) {
+			Display.setBrightness(-7);
+		} else if ((ambLight < 200) and (ambLight >= 160)) {
+			Display.setBrightness(-9);
+		} else if ((ambLight < 150) and (ambLight >= 110)) {
+			Display.setBrightness(-12);
+		} else if (ambLight < 100) {
+			Display.setBrightness(-15);
 		}
-	} else {
-		/* 0 o'clock is an exception, we don't want to see "00.00", we
-		   want see "0.00" or "0 00", so we have to use this "hack" */
-		if (dot) {
-			d = float(clock.minute) / 100;
-			Display.setNumber(d, 2);
-		} else {
-			sprintf(str, "%2d%02d", clock.hour, clock.minute);
-			Display.setChars(str);
-		}
-	}
-
-	/* ambient light compensation
-	 * ambLight can be in range of 0..1023, if it 800, it has point to use fullbright
-	 */
-	if (ambLight >= 940) {
-		Display.setBrightness(100);
-	} else if ((ambLight < 900) and (ambLight >= 840)) {
-		Display.setBrightness(95);
-	} else if ((ambLight < 800) and (ambLight >= 735)) {
-		Display.setBrightness(70);
-	} else if ((ambLight < 700) and (ambLight >= 635)) {
-		Display.setBrightness(25);
-	} else if ((ambLight < 600) and (ambLight >= 530)) {
-		Display.setBrightness(15);
-	} else if ((ambLight < 500) and (ambLight >= 430)) {
-		Display.setBrightness(12);
-	} else if ((ambLight < 400) and (ambLight >= 325)) {
-		Display.setBrightness(10);
-	} else if ((ambLight < 300) and (ambLight >= 220)) {
-		Display.setBrightness(8);
-	} else if ((ambLight < 200) and (ambLight >= 110)) {
-		Display.setBrightness(7);
-	} else if (ambLight < 100) {
-		Display.setBrightness(6);
 	}
 
 	Display.refreshDisplay();
 }
 
+void updateTimeStr(uint8_t h, uint8_t m)
+{
+	char str[4];
+	float d;
+
+	// make blinking dot
+	if (h > 0) {
+		if (dot) {
+			Display.setNumber((h * 100 + m), 2);
+		} else {
+			Display.setNumber((h * 100 + m));
+		}
+	} else {
+		/* 0 o'clock is an exception, we don't want to see "00.00", we
+		   want see "0.00" or "0 00", so we have to use this "hack" */
+		if (dot) {
+			d = float(m) / 100;
+			Display.setNumber(d, 2);
+		} else {
+			sprintf(str, "%2d%02d", h, m);
+			Display.setChars(str);
+		}
+	}
+	
+}
 /* vim: set filetype=cpp: */