Published May 5, 2020 © CC BY-NC-SA

ESP8266 NTP Clock on SSD1306 OLED (Arduino IDE)

A simple web clock utilizing a OLED library called U8x8lib which has a lot of fonts.

BeginnerProtip18,980

ESP8266 NTP Clock on SSD1306 OLED (Arduino IDE)

Things used in this project

Hardware components

Espressif Wemos D1 Mini

ElectroPeak 0.96" OLED 64x128 Display Module

Software apps and online services

Arduino IDE

Story

Note: the code has been (again) updated in Dec 2022 thanks for some nice feedback. Now the code should work for both ESP8266 and ESP32 (although it runs smoother on ESP8266 - WeMos D1, NodeMCU, etc.).

Originally I use WiFiMulti so that users can set multiple APs (hence the clock will work in different places) but it has been proved to be problematic on ESP32.

Another simple project. Since the main font is big enough, you can use it as a real clock on your desk. Set the WiFi AP name, password and timezone offset (hour) before uploading.

The ESP8266 board will update its board time every 15 minutes via the NTP (Network Time Protocol) server and constantly display date and time on a "0.96 SSD1306 OLED display. The libraries I used are NTPClient and u8g2.

u8g2 (U8x8lib) is actually an interesting OLED library, which has a lot of fonts in different sizes. The sizes are a bit confusing though; the smallest size are 8x8 pixels per character, so "1x2" means 8x16 pixels, "3x6" is 24x36 pixels, etc. The x and y parameters of u8x8.drawString method are referring to the characters, hence x is 0-15 and y is 0-7.

u8g2 also works for a lot of different OLEDs and LCDs, including those Chinese-made OLEDs which don't return I2C ACK signals (which may cause other drivers non-working). This is exactly how I found this library - I got one of these from other people a while ago.

Code

ESP8266 NTP Clock

#ifdef ESP8266
#include <ESP8266WiFi.h>
#endif

#ifdef ESP32
#include <WiFi.h>
#endif

#include <NTPClient.h>
#include <WiFiUdp.h>
#include <Wire.h>
#include <U8x8lib.h>

// ========== user settings ==========

const char          *ssid          = "";             // your wifi name
const char          *pw            = "";             // your wifi password
const char          *ntpServer     = "pool.ntp.org"; // change it to local NTP server if needed
const unsigned long updateDelay    = 900;            // NTP update interval (unit: seconds, default: 15 min)
const long          timezoneOffset = 0;              // timezone offset (unit: hours)

#define SCL_PIN SCL  // SCL pin of OLED. Default: D1 (ESP8266) or D22 (ESP32)
#define SDA_PIN SDA  // SDA pin of OLED. Default: D2 (ESP8266) or D21 (ESP32)

// ====================================

const String  weekDays[7] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
unsigned long lastCheckTime = 0;
unsigned int  second_prev = 0;
bool          colon_switch = false;

// NTPClient: https://github.com/arduino-libraries/NTPClient
WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP, ntpServer);

// U8X8 Display constructors: https://github.com/olikraus/u8g2/wiki/u8x8setupcpp
// U8X8 Fonts: https://github.com/olikraus/u8g2/wiki/u8x8reference
U8X8_SSD1306_128X64_NONAME_SW_I2C u8x8(SCL_PIN, SDA_PIN, U8X8_PIN_NONE);

void setup() {

  // serial baud rate: 115200
  Serial.begin(115200);

  // initialize OLED
  u8x8.begin();
  u8x8.setBusClock(400000);
  u8x8.setFont(u8x8_font_7x14B_1x2_f);
  u8x8.drawString(0, 0, "Connecting");
  u8x8.drawString(0, 3, "  to WiFi...");

  // connect to wifi
  Serial.println("Connecting to WiFi...");
  WiFi.disconnect();
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, pw);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(500);
  }
  Serial.println("\nConnected. IP:");
  Serial.println(WiFi.localIP());

  // clear OLED
  u8x8.clear();

  // setup NTPClient
  timeClient.setUpdateInterval(updateDelay * 1000);
  timeClient.setTimeOffset(timezoneOffset * 60 * 60);
  timeClient.begin();
  while (!timeClient.update()) timeClient.forceUpdate();
  lastCheckTime = millis();

}

void loop() {

  // check wifi status and NTP updates
  if (millis() - lastCheckTime >= updateDelay * 1000) {
    // reconnect wifi if needed
    if (WiFi.status() != WL_CONNECTED) WiFi.reconnect();
    // update NTP (and force update if needed)
    if (!timeClient.update()) timeClient.forceUpdate();
    lastCheckTime = millis();
  }

  // extract second from board's internal clock
  unsigned int second = timeClient.getSeconds();

  // when the second number changes, extract the rest of values
  // then re-draw the clock texts
  if (second != second_prev) {

    colon_switch = !colon_switch;

    time_t rawtime = timeClient.getEpochTime();
    struct tm * ti;
    ti = localtime(&rawtime);
    unsigned int year = ti->tm_year + 1900;
    unsigned int month = ti->tm_mon + 1;
    unsigned int day = ti->tm_mday;
    unsigned int hour = timeClient.getHours();
    unsigned int minute = timeClient.getMinutes();

    String fYear = String(year);
    String fDate = (month < 10 ? "0" : "") + String(month) + "/" + (day < 10 ? "0" : "") + String(day);
    String fTime = (hour < 10 ? "0" : "") + String(hour) + (colon_switch ? ":" : " ") + (minute < 10 ? "0" : "") + String(minute);
    String weekDay = weekDays[timeClient.getDay()];

    Serial.println("Board time: " + fYear + "/" + fDate + " (" + weekDay + ") " + timeClient.getFormattedTime());

    u8x8.setFont(u8x8_font_lucasarts_scumm_subtitle_o_2x2_f);
    u8x8.drawString(1, 0, strcpy(new char[fDate.length() + 1], fDate.c_str()));
    u8x8.setFont(u8x8_font_pxplusibmcga_f);
    u8x8.drawString(12, 0, strcpy(new char[fYear.length() + 1], fYear.c_str()));
    u8x8.setFont(u8x8_font_victoriamedium8_r);
    u8x8.drawString(12, 1, strcpy(new char[weekDay.length() + 1], weekDay.c_str()));
    u8x8.setFont(u8x8_font_inb33_3x6_f);
    u8x8.drawString(1, 2, strcpy(new char[fTime.length() + 1], fTime.c_str()));

  }

  second_prev = second;

  delay(200);

}