Lesson 33 RTC DS1302

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Introduction

DS1302 is a trickle charging clock chip, launched by DALLAS in America. With a built-in real-time clock/calendar and a 31-byte static RAM, it can communicate with MCU through simple serial interfaces. The real-time clock/calendar circuit provides information about second, minute, hour, day, week, month, and year. DS1302 can automatically adjust the number of days per month and days in leap year. You can determine to use a 24-hour or 12-hour system by AM/PM selection.

Required Components

 1 * Raspberry Pi

– 1 * Breadboard

– 1 * DS1302 RTC module

– 1 * 5-Pin anti-reverse cable

Experimental Principle

Interfacing the DS1302 with a microprocessor is simplified by using synchronous serial communication. Only three wires are required to communicate with the clock/RAM: RST, serial data (SDA) and serial clock (SCL). SDA can be transferred to and from the clock/RAM one byte at a time or in a burst of up to 31 bytes.

After the time of the DS1302 is set manually, the MCU starts to read the accurate time and date returned by DS1302.

The schematic diagram of the module is as shown below:

Experimental Procedures

Step 1: Build the circuit. 

Raspberry PiGPIO Extension BoardRTC DS1302 Module
GPIO4GPIO23SCL
GPIO5GPIO24I/O or SDA
GPIO6GPIO25RST
3.3V3V3VCC
GNDGNDGND

For C Users:

Step 2: Change directory. 

    cd /home/pi/SunFounder_SensorKit_for_RPi2/C/33_ds1302/

Step 3: Compile:

    gcc rtc_ds1302.c -lwiringPi -lwiringPiDev

Step 4: Set up time by:

    sudo ./a.out -sdsc

Set year, month, date as YYYYMMDD

Set hour, minute, second as HHMMSS(24-hour clock)

Set weekday (0 as Sunday)

Step 5: Run:

    sudo ./a.out 

For Python Users:

Step 2: Change directory. 

    cd /home/pi/SunFounder_SensorKit_for_RPi2/Python/

Step 3: Run.

    sudo python3 33_ds1302.py

Now you can see the time on the screen.