added internet time which is shown in the main first screen

include/internet_time.h

@@ -0,0 +1,36 @@
+#ifndef INTERNET_TIME_H
+#define INTERNET_TIME_H
+
+#include <Arduino.h>
+
+struct InternetTimeInfo
+{
+  bool valid;
+  uint16_t year;
+  uint8_t month;
+  uint8_t day;
+  uint8_t hour;
+  uint8_t minute;
+};
+
+class InternetTime
+{
+public:
+  InternetTime();
+  void update(unsigned long now, bool wifiConnected);
+  InternetTimeInfo info() const;
+  bool consumeDirty();
+
+private:
+  void fetch(unsigned long now);
+  void updateCurrentTime(unsigned long now);
+  InternetTimeInfo infoFromEpoch(unsigned long epoch) const;
+
+  unsigned long lastEpoch_;
+  unsigned long lastSyncMillis_;
+  unsigned long nextAttempt_;
+  InternetTimeInfo current_;
+  bool dirty_;
+};
+
+#endif

include/screens.h

@@ -4,9 +4,11 @@
 #include <U8g2lib.h>
 
 #include "am2302_sensor.h"
+#include "internet_time.h"
 #include "wifi_connection.h"
 
-void drawScreen1(U8G2 &u8g2);
+void setInternetTimeInfo(InternetTimeInfo timeInfo);
+void drawTimeScreen(U8G2 &u8g2);
 void drawHelloWorldScreen(U8G2 &u8g2);
 void drawInternetConnectionScreen(U8G2 &u8g2, WifiConnectionInfo wifiInfo);
 void setEnvironmentReading(Am2302Reading reading);

include/wifi_credentials.example.h

@@ -4,4 +4,7 @@
 const char WIFI_SSID[] = "your-wifi-name";
 const char WIFI_PASSWORD[] = "your-wifi-password";
 
+// Offset from UTC in seconds. Examples: Finland winter 7200, Finland summer 10800.
+#define TIME_UTC_OFFSET_SECONDS 0
+
 #endif

src/internet_time.cpp

@@ -0,0 +1,142 @@
+#include "internet_time.h"
+
+#include <WiFi101.h>
+
+#include "wifi_credentials.h"
+
+#ifndef TIME_UTC_OFFSET_SECONDS
+#define TIME_UTC_OFFSET_SECONDS 0
+#endif
+
+namespace
+{
+const unsigned long retryInterval = 15000;
+const unsigned long refreshInterval = 3600000;
+const unsigned long secondsPerDay = 86400;
+
+bool isLeapYear(uint16_t year)
+{
+  return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
+}
+
+uint8_t daysInMonth(uint16_t year, uint8_t month)
+{
+  const uint8_t days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+  if (month == 2 && isLeapYear(year)) {
+    return 29;
+  }
+  return days[month - 1];
+}
+
+unsigned long applyTimeOffset(unsigned long epoch)
+{
+  if (TIME_UTC_OFFSET_SECONDS >= 0) {
+    return epoch + TIME_UTC_OFFSET_SECONDS;
+  }
+
+  const unsigned long offset = static_cast<unsigned long>(-TIME_UTC_OFFSET_SECONDS);
+  return epoch > offset ? epoch - offset : 0;
+}
+}
+
+InternetTime::InternetTime()
+    : lastEpoch_(0),
+      lastSyncMillis_(0),
+      nextAttempt_(0),
+      current_({false, 0, 0, 0, 0, 0}),
+      dirty_(true) {}
+
+void InternetTime::update(unsigned long now, bool wifiConnected)
+{
+  if (current_.valid) {
+    updateCurrentTime(now);
+  }
+
+  if (!wifiConnected) {
+    return;
+  }
+
+  if (now >= nextAttempt_) {
+    fetch(now);
+  }
+}
+
+InternetTimeInfo InternetTime::info() const
+{
+  return current_;
+}
+
+bool InternetTime::consumeDirty()
+{
+  const bool d = dirty_;
+  dirty_ = false;
+  return d;
+}
+
+void InternetTime::fetch(unsigned long now)
+{
+  const unsigned long epoch = WiFi.getTime();
+  nextAttempt_ = now + retryInterval;
+
+  if (epoch == 0) {
+    return;
+  }
+
+  lastEpoch_ = epoch;
+  lastSyncMillis_ = now;
+  nextAttempt_ = now + refreshInterval;
+  updateCurrentTime(now);
+}
+
+void InternetTime::updateCurrentTime(unsigned long now)
+{
+  const unsigned long elapsedSeconds = (now - lastSyncMillis_) / 1000;
+  const InternetTimeInfo updated = infoFromEpoch(lastEpoch_ + elapsedSeconds);
+
+  if (!current_.valid ||
+      current_.year != updated.year ||
+      current_.month != updated.month ||
+      current_.day != updated.day ||
+      current_.hour != updated.hour ||
+      current_.minute != updated.minute) {
+    current_ = updated;
+    dirty_ = true;
+  }
+}
+
+InternetTimeInfo InternetTime::infoFromEpoch(unsigned long epoch) const
+{
+  unsigned long adjustedEpoch = applyTimeOffset(epoch);
+  unsigned long days = adjustedEpoch / secondsPerDay;
+  unsigned long secondsToday = adjustedEpoch % secondsPerDay;
+
+  uint16_t year = 1970;
+  while (true) {
+    const uint16_t yearDays = isLeapYear(year) ? 366 : 365;
+    if (days < yearDays) {
+      break;
+    }
+    days -= yearDays;
+    year++;
+  }
+
+  uint8_t month = 1;
+  while (true) {
+    const uint8_t monthDays = daysInMonth(year, month);
+    if (days < monthDays) {
+      break;
+    }
+    days -= monthDays;
+    month++;
+  }
+
+  InternetTimeInfo info = {
+    true,
+    year,
+    month,
+    static_cast<uint8_t>(days + 1),
+    static_cast<uint8_t>(secondsToday / 3600),
+    static_cast<uint8_t>((secondsToday % 3600) / 60)
+  };
+  return info;
+}

src/main.cpp

@@ -4,6 +4,7 @@
 
 #include "am2302_sensor.h"
 #include "carousel.h"
+#include "internet_time.h"
 #include "menu.h"
 #include "screens.h"
 #include "wifi_connection.h"
@@ -16,6 +17,7 @@ uint8_t buttonNext = A4;
 uint8_t buttonSelect = A5;
 Am2302Sensor am2302(A3);
 WifiConnection wifiConnection;
+InternetTime internetTime;
 
 enum class AppMode
 {
@@ -26,7 +28,7 @@ enum class AppMode
 };
 
 Screen screens[] = {
-  { drawScreen1 },
+  { drawTimeScreen },
   { drawEnvironmentScreen },
   { drawWeatherIconScreen }
 };
@@ -142,6 +144,14 @@ void drawActiveView()
 void loop(){
   const unsigned long now = millis();
   wifiConnection.update(now);
+  internetTime.update(now, wifiConnection.info().connected);
+
+  if (internetTime.consumeDirty()) {
+    setInternetTimeInfo(internetTime.info());
+    if (appMode == AppMode::Carousel) {
+      carousel.requestRedraw();
+    }
+  }
 
   if (appMode == AppMode::Carousel) {
     carousel.update(now);

src/screens.cpp

@@ -3,6 +3,15 @@
 namespace
 {
 Am2302Reading environmentReading = {0.0F, 0.0F, false};
+InternetTimeInfo internetTimeInfo = {false, 0, 0, 0, 0, 0};
+
+void printTwoDigits(U8G2 &u8g2, uint8_t value)
+{
+  if (value < 10) {
+    u8g2.print("0");
+  }
+  u8g2.print(value);
+}
 
 void drawSun(U8G2 &u8g2, uint8_t x, uint8_t y)
 {
@@ -27,10 +36,33 @@ void drawCloud(U8G2 &u8g2, uint8_t x, uint8_t y)
 }
 }
 
-void drawScreen1(U8G2 &u8g2)
+void setInternetTimeInfo(InternetTimeInfo timeInfo)
 {
-  u8g2.setFont(u8g2_font_ncenB14_tr);
-  u8g2.drawStr(0, 20, "Screen 1");
+  internetTimeInfo = timeInfo;
+}
+
+void drawTimeScreen(U8G2 &u8g2)
+{
+  if (!internetTimeInfo.valid) {
+    u8g2.setFont(u8g2_font_6x12_tr);
+    u8g2.drawStr(0, 24, "Time has not");
+    u8g2.drawStr(0, 40, "been updated");
+    return;
+  }
+
+  u8g2.setFont(u8g2_font_6x12_tr);
+  u8g2.setCursor(0, 14);
+  printTwoDigits(u8g2, internetTimeInfo.day);
+  u8g2.print(".");
+  printTwoDigits(u8g2, internetTimeInfo.month);
+  u8g2.print(".");
+  u8g2.print(internetTimeInfo.year);
+
+  u8g2.setFont(u8g2_font_ncenB24_tr);
+  u8g2.setCursor(0, 54);
+  printTwoDigits(u8g2, internetTimeInfo.hour);
+  u8g2.print(":");
+  printTwoDigits(u8g2, internetTimeInfo.minute);
 }
 
 void drawHelloWorldScreen(U8G2 &u8g2)