ESP32 IoT Clock: Sync Time from the Internet (No RTC)

1#include <ESP8266WiFi.h>
2#include <WiFiClientSecure.h>
3#include <time.h>
4
5const char* ssid = "Dziubym";
6const char* password = "Mikigosia1";
7
8WiFiClientSecure client;
9
10
11unsigned long getUnixTimestamp() {
12  client.setInsecure(); // Skip certificate validation
13  
14  if (client.connect("aisenseapi.com", 443)) {
15    client.println("GET /services/v1/timestamp HTTP/1.1");
16    client.println("Host: aisenseapi.com");
17    client.println("Connection: close");
18    client.println();
19
20    while (client.connected() || client.available()) {
21      String line = client.readStringUntil('\n');
22      if (line.indexOf("timestamp") >= 0) {
23        int start = line.indexOf(":") + 1;
24        int end = line.indexOf("}", start);
25        unsigned long timestamp = line.substring(start, end).toInt();
26        client.stop();
27        return timestamp;
28      }
29    }
30    client.stop();
31  }
32  return 0; // return 0 if failed
33}
34
35
36unsigned long startUnix = 0;      // reference Unix time (Y)
37unsigned long lastSyncMillis = 0; // millis() at last update (U)
38unsigned long currentUnix = 0;
39unsigned long lastDisplayedSecond = 0;
40bool syncedToday = false;  // replaces lastSyncCheck
41struct tm *timeInfo = localtime((time_t*)&startUnix);
42
43void setup() {
44  Serial.begin(9600);
45  delay(2000);
46  Serial.println("Connecting to WiFi...");
47  delay(2000);
48  Serial.println("Connecting to WiFi...");
49  WiFi.begin(ssid, password);
50  while (WiFi.status() != WL_CONNECTED) {
51    delay(500);
52    Serial.print(".");
53  }
54  Serial.println("\nWiFi connected.");
55
56  startUnix = getUnixTimestamp();  // get reference time (Y)
57  lastSyncMillis = millis();       // mark sync moment (U)
58
59  if (startUnix > 0) {
60    Serial.print("Initial Unix time: ");
61    Serial.println(startUnix);
62  } else {
63    Serial.println("Failed to get Unix timestamp.");
64  }
65}
66
67void loop() {
68  
69  unsigned long elapsedSec = (millis() - lastSyncMillis) / 1000;
70  unsigned long currentUnix = startUnix + elapsedSec;
71
72  if (elapsedSec != lastDisplayedSecond) {   // new second tick
73  lastDisplayedSecond = elapsedSec;
74
75    // Convert Unix → human-readable
76    time_t now = currentUnix;
77    tm *timeInfo = localtime(&now); // use gmtime for UTC
78    char buffer[30];
79    strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", timeInfo);
80
81    Serial.print("Time: ");
82    Serial.print(buffer);
83    Serial.print(" syncedToday:");
84    Serial.println(syncedToday);
85   
86  }
87
88  // Sync every day at 1:00 AM
89  //struct tm *t = localtime((time_t*)&currentUnix);
90  if (timeInfo->tm_hour == 18 && timeInfo->tm_min == 25 && !syncedToday) {
91    Serial.println("1:00 AM reached — syncing time from internet...");
92    unsigned long newUnix = getUnixTimestamp();
93    if (newUnix > 0) {
94      startUnix = newUnix;
95      lastSyncMillis = millis();
96      Serial.println("Time updated successfully.");
97      syncedToday = true;
98    } else {
99      Serial.println("Time update failed.");
100    }
101    delay(1000); // avoid multiple triggers within the same second
102  }
103  // Reset the sync flag at 1:01 AM
104  if (timeInfo->tm_hour == 18 && timeInfo->tm_min   == 26) {
105    syncedToday = false;
106  }
107}

1#include <Arduino.h>
2#include <WiFi.h>
3#include <WiFiClientSecure.h>
4#include <U8g2lib.h>
5#include <Wire.h>
6#include <time.h>
7
8// ---- WiFi settings ----
9const char* ssid = "Dziubym";
10const char* password = "Mikigosia1";
11
12// ---- OLED pins ----
13#define SDA_PIN 5
14#define SCL_PIN 6
15U8G2_SSD1306_72X40_ER_F_HW_I2C u8g2(U8G2_R0, /* reset=*/ U8X8_PIN_NONE);
16
17// ---- HTTPS client ----
18WiFiClientSecure client;
19
20// ---- Timekeeping variables ----
21unsigned long startUnix = 0;
22unsigned long lastSyncMillis = 0;
23unsigned long lastDisplayedSecond = 0;
24bool syncedToday = false;  // replaces lastSyncCheck
25struct tm *timeInfo = localtime((time_t*)&startUnix);
26
27// ---- Draw a message on OLED ----
28void drawOLEDMessage(const char* msg) {
29  
30  u8g2.clearBuffer();
31  u8g2.setDrawColor(1);
32  u8g2.setFont(u8g2_font_5x8_tr);
33  u8g2.drawStr(0, 12, msg);
34  u8g2.sendBuffer();
35}
36
37// ---- Get Unix timestamp from API ----
38unsigned long getUnixTimestamp() {
39  drawOLEDMessage("Fetching time..."); // display while fetching
40
41  client.setInsecure(); // skip certificate check
42  if (client.connect("aisenseapi.com", 443)) {
43    client.println("GET /services/v1/timestamp HTTP/1.1");
44    client.println("Host: aisenseapi.com");
45    client.println("Connection: close");
46    client.println();
47
48    while (client.connected() || client.available()) {
49      String line = client.readStringUntil('\n');
50      if (line.indexOf("timestamp") >= 0) {
51        int start = line.indexOf(":") + 1;
52        int end = line.indexOf("}", start);
53        unsigned long timestamp = line.substring(start, end).toInt();
54        client.stop();
55        return timestamp;
56      }
57     }
58    client.stop();
59  }
60  return 0; // failed
61}
62
63// ---- Draw time/date on OLED ----
64void drawTimeDisplay(time_t currentUnix) {
65   tm *timeInfo = localtime(&currentUnix);
66
67  char timeStr[9];  // "HH:MM:SS"
68  snprintf(timeStr, sizeof(timeStr), "%02d:%02d:%02d",
69           timeInfo->tm_hour, timeInfo->tm_min, timeInfo->tm_sec);
70
71  char dateStr[20]; // "Wed Oct15 2025"
72  strftime(dateStr, sizeof(dateStr), "%a %b%d %Y", timeInfo);
73
74  u8g2.clearBuffer();
75  u8g2.setDrawColor(1);
76  u8g2.setFont(u8g2_font_5x8_tr);
77  u8g2.drawStr(0, 8, dateStr);
78
79  u8g2.setDrawColor(1);
80  u8g2.drawBox(0, 16, 72, 24);
81
82  u8g2.setDrawColor(0);
83  u8g2.setFont(u8g2_font_logisoso16_tf);
84  u8g2.drawStr(0, 36, timeStr);
85  u8g2.sendBuffer();
86}
87
88// ---- Setup ----
89void setup() {
90  Wire.begin(SDA_PIN, SCL_PIN);
91  u8g2.begin();
92
93  drawOLEDMessage("Connecting WiFi...");
94  WiFi.begin(ssid, password);
95  while (WiFi.status() != WL_CONNECTED) {
96    delay(300);
97  }
98  drawOLEDMessage("WiFi connected");
99
100  // Initial sync
101  startUnix = getUnixTimestamp();
102  lastSyncMillis = millis();
103
104  if (startUnix > 0) {
105    drawOLEDMessage("Time synced");
106    delay(1000);
107  } else {
108    drawOLEDMessage("Sync failed");
109    delay(1000);
110  }
111}
112
113// ---- Loop ----
114void loop() {
115  unsigned long nowMs = millis();
116  unsigned long elapsedSec = (nowMs - lastSyncMillis) / 1000;
117  unsigned long currentUnix = startUnix + elapsedSec;
118
119 // Get local time struct
120  time_t now = currentUnix;
121  struct tm *timeInfo = localtime(&now);
122
123  // Display update once per second
124  if (elapsedSec != lastDisplayedSecond) {
125    lastDisplayedSecond = elapsedSec;
126    drawTimeDisplay(currentUnix);
127  }
128
129
130  // Sync every day at 1:00 AM
131  //struct tm *t = localtime((time_t*)&currentUnix);
132  if (timeInfo->tm_hour == 6 && timeInfo->tm_min == 18 && !syncedToday) {
133    drawOLEDMessage("Daily sync...");
134    delay(2000);
135    unsigned long newUnix = getUnixTimestamp();
136    if (newUnix > 0) {
137      startUnix = newUnix;
138      lastSyncMillis = millis();
139      drawOLEDMessage("Sync OK");
140      delay(2000);
141    } else {
142      drawOLEDMessage("Sync failed");
143      delay(2000);
144    }
145    syncedToday = true;
146  }
147
148  // Reset the sync flag at 1:01 AM
149  if (timeInfo->tm_hour == 6 && timeInfo->tm_min   == 19) {
150    syncedToday = false;
151  }
152
153  delay(50);
154}

1#include <time.h>
2
3void setup() {
4  Serial.begin(9600);
5  delay(1000);
6  Serial.println("");
7  delay(3000);
8  
9  // Friday, 20 October 2023 16:00:00
10  time_t now = 1697817600;
11  struct tm *timeInfo = gmtime(&now);
12
13  char buffer[30];
14  strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", timeInfo);
15  Serial.println(buffer);  // Output: "2023-10-20 00:00:00"
16  
17  Serial.printf("Hour: %d, Minute: %d, Second: %d\n",
18              timeInfo->tm_hour,
19              timeInfo->tm_min,
20              timeInfo->tm_sec);
21}
22void loop (){}

1#include <ESP8266WiFi.h>
2#include <WiFiClientSecure.h>
3
4const char* ssid = "Dziubym";
5const char* password = "Mikigosia1";
6
7WiFiClientSecure client;
8
9// Function to get Unix timestamp from API
10unsigned long getUnixTimestamp() {
11  client.setInsecure(); // Skip certificate validation
12  
13  if (client.connect("aisenseapi.com", 443)) {
14    client.println("GET /services/v1/timestamp HTTP/1.1");
15    client.println("Host: aisenseapi.com");
16    client.println("Connection: close");
17    client.println();
18
19    while (client.connected() || client.available()) {
20      String line = client.readStringUntil('\n');
21      Serial.println(line);
22      if (line.indexOf("timestamp") >= 0) {
23        int start = line.indexOf(":") + 1;
24        int end = line.indexOf("}", start);
25        unsigned long timestamp = line.substring(start, end).toInt();
26        client.stop();
27        return timestamp;
28      }
29    }
30    client.stop();
31  }
32
33  return 0; // return 0 if failed
34}
35
36void setup() {
37  Serial.begin(9600);
38  WiFi.begin(ssid, password);
39  
40  Serial.print("Connecting to WiFi");
41  while (WiFi.status() != WL_CONNECTED) {
42    delay(500);
43    Serial.print(".");
44  }
45  Serial.println("\nWiFi connected");
46  
47  unsigned long timestamp = getUnixTimestamp();
48    delay(3000);
49    if (timestamp > 0) {
50    Serial.print("Unix time: ");
51    Serial.println(timestamp);
52  } else {
53    Serial.println("Failed to get Unix timestamp.");
54  }
55}
56
57void loop() {
58  // Empty - only run once in setup
59}