An Arduino Uno drives a 16×2 I²C LCD and keeps accurate time without an RTC by requesting NTP data over Wi‑Fi. Connectivity is provided by an ESP‑01 (ESP8266) running AT firmware and controlled through the WiFiEsp library.
- No dedicated RTC—time is fetched from pool.ntp.org every hour via NTP.
- 16×2 I²C LCD displays current time/date with a configurable UTC offset.
- WiFiEsp + SoftwareSerial allows the Uno to use an ESP‑01 while keeping hardware serial free for logging.
wifi_credentials.hisolates SSID/password for easy updates.
| Component | Notes |
|---|---|
| Arduino Uno (5 V board) | Drives LCD + SoftwareSerial |
| ESP‑01 (ESP8266) with AT firmware | Use stable AT firmware (e.g., v1.5.x) at 9600 baud |
| 16×2 LCD with PCF8574 I²C backpack | Default address 0x27 (run I²C scanner to confirm) |
| Stable 3.3 V regulator (≥300 mA) | Powers the ESP‑01; don’t use the Uno’s 3.3 V pin |
| Level shifter / resistor divider | Drops Arduino TX (5 V) down to ESP RX (3.3 V) |
| Dupont wires + 10 kΩ pull-ups | Pull CH_PD, GPIO0, GPIO2 high |
ESP‑01 ↔ Uno
| ESP Pin | Uno / Notes |
|---|---|
| VCC, EN/CH_PD | Regulated 3.3 V (tie EN high via 10 kΩ) |
| GND | Common ground |
| TX | D2 (ESP_RX_PIN) |
| RX | D3 (ESP_TX_PIN) through divider (e.g., 1 kΩ/2 kΩ) |
| GPIO0, GPIO2 | 3.3 V via 10 kΩ pull-ups (GPIO0 low only when flashing firmware) |
| RST | 3.3 V via 10 kΩ (optional button to GND) |
LCD (I²C)
- VCC → 5 V
- GND → GND
- SDA → A4
- SCL → A5
- Install libraries (Sketch → Include Library → Manage Libraries…)
- WiFiEsp, NTPClient, Time (TimeLib), LiquidCrystal_I2C (NewLiquidCrystal).
- Prep the ESP‑01
- Connect via USB‑serial adapter, ensure AT firmware responds.
- Lock baud to 9600:
AT+UART_DEF=9600,8,1,0,0. - Verify it can join your AP with
AT+CWJAP="SSID","PASSWORD".
- Configure Wi‑Fi credentials
- Edit
1_internet_time_clock/wifi_credentials.h.
- Edit
- Upload
- Disconnect ESP‑01 from pins 0/1 while flashing.
- Select Board → Arduino Uno and the correct COM port, then upload.
- Reconnect ESP‑01 to D2/D3 afterwards.
- Monitor
- Open Serial Monitor at 9600 baud to view WiFiEsp logs (
Connecting to ...,Connected to WiFi). - LCD shows
TIME/DATEonce NTP data is received. AdjustUTC_OFFSET_SECONDSto match your timezone.
- Open Serial Monitor at 9600 baud to view WiFiEsp logs (
- LCD only shows a blinking block: run the I²C scanner to confirm the address, check SDA/SCL wiring, and adjust contrast.
WiFiEsp >>> TIMEOUTor “ESP-01 not responding”: ensure a solid 3.3 V supply, correct TX/RX wiring, proper pull-ups, and that AT firmware responds at 9600 baud.- Fails to connect to Wi‑Fi: double-check SSID/password, keep ESP close to the router, ensure STA mode (
AT+CWMODE=1), and consider channel changes if your router uses channels 12/13. - Time offset incorrect: update
UTC_OFFSET_SECONDSin the sketch (seconds relative to UTC). Add or remove 3600 seconds when daylight saving changes.
