ESP32 with DS1307 RTC Module

15-07-2025

⏰ What is DS1307 RTC?

The DS1307 is a real-time clock IC by Maxim Integrated that keeps track of:

Seconds
Minutes
Hours (12 or 24-hour mode)
Day, Date, Month, Year
Automatically adjusts for leap years

✅ It communicates with microcontrollers using SPI (Serial Peripheral Interface) — unlike the more common DS1307, which uses I2C.

🔍 Key Features

Feature	Details
Interface	SPI
Voltage	2.0V – 5.5V
Timekeeping	Seconds, Minutes, Hours, Day, Date
Battery backup	Yes (CR1220 or CR2032 coin cell)
Oscillator	Requires external 32.768 kHz crystal
Alarm + Square Wave	Built-in (configurable)

🧰 Components Required

Component	Description
ESP32 board	Microcontroller
DS1306 RTC module	With CR2032 battery and SPI pins
Jumper wires	Male-to-female preferred
Breadboard	For clean prototyping
Arduino IDE	To program ESP32

🔌 DS1307 to ESP32 Wiring (SPI)

DS1306 Pin	ESP32 Pin	Description
VCC	3.3V or 5V	Power supply
GND	GND	Ground
SCLK	GPIO 18	SPI Clock
MISO	GPIO 19	SPI MISO (Data In)
MOSI	GPIO 23	SPI MOSI (Data Out)
CS	GPIO 5	SPI Chip Select

Make sure you connect the battery for backup timekeeping.

📚 Step-by-Step in Arduino IDE

✅ Step 1: Install Required Library

Since DS1306 uses SPI, and isn’t as widely supported as DS3231 or DS1307, we’ll use the DS1306 library (by Paul Stoffregen or compatible fork).

Go to Sketch > Include Library > Manage Libraries
Search for and install:
- DS1306RTC (if not found, you may need to manually add)

You may also use RTClib but it doesn’t directly support DS1306.

⏱️ What’s a Better Option?

If you're using this RTC for standard timekeeping, you might find DS1307 or DS3231 (I2C-based) much easier and better supported in Arduino.

If you're bound to DS1306, I can help you:

Add a working library
Write custom SPI functions to read/set time
Convert to RTClib-compatible class

🧠 Applications of RTC Modules (like DS1307)

Application	Description
⏰ Digital Clock	Show real-world time & date
📝 Data Logging	Timestamp for sensor readings
🔋 Power Saving	Wake up ESP32 at a set time
📦 IoT Projects	Sync events to time-based triggers
📷 Camera Trap	Time-stamp wildlife photos/videos