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        Pi RTC (DS1307) The Pi RTC is based on the clock chip DS1307, it can provide a real-time clock(RTC) for raspberry pi via the I2C interface. Real-time clock of this module counts seconds,minutes, hours, date of the month,month, day of the week, and year with leap-year compensation valid up to 2100. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. If you want to keep this module timing when the Raspberry Pi is powered off, you need to put a 3-Volt CR1225 lithium cell in the battery-holder. Note The battery is not included. Features        Support Raspberry Pi 2/ 3 B/B+ Zero Suport seconds,minuutes,hours,day of week,month, year Support 24-hour or 12-hour format with AM/PM indicator 56-byte, battery-backed, nonvolatile (NV) RAM for data storage Two-wire serial interface Programmable squarewave output signal Automatic power-fail detect and switch circuitry     Specification Item Value Operating Voltage 5V Interface I2C I2C Address 0x68 Typical applications Any applications need Real Time on Raspberry. Pin Out Note RX/TX is not used in this module, but the 5x2 header takes up the RX/TX pin of the Raspberry Pi, so we bring the RX/TX out and come with a 2pin header.     Schemaitc Bi-directional level shifter circuit This is a typical Bi-directional level shifter circuit to connect two different voltage section of an I2C bus. The I2C bus of Raspberry Pi uses 3.3V, however the chip DS1307 works at 5V, so this circuit will be needed. In the schematic above, Q1 and Q2 are N-Channel MOSFET 2N7002A, which act as a bidirectional switch. In order to better understand this part, you can refer to the AN10441 Platforms Supported Arduino   Raspberry Pi BeagleBone Wio LinkIt ONE   Getting Started Materials required Raspberry Pi Pi RTC(DS1307) Note Please plug the USB cable gently, otherwise you may damage the port. Please use the USB cable with 4 wires inside, the 2 wires cable can't transfer data. If you are not sure about the wire you have, you can click here to buy Install The driver we provide only applied for Raspbian Jessie/Stretch. Tip If you do not know how to use a raspberry pi, please check here before start.  Step 1. Driver Installation Tap the following command in your terminal 1 git clone https://github.com/Seeed-Studio/pi-hats.git   When the download finish, tap the following command in your terminal 1 2 cd pi-hats sudo ./install.sh -u rtc_ds1307    Step 2. Power off Raspberry Pi 1 sudo shutdown -h now        Step 3. Insert the HAT to Raspberry Pi Please make sure plug the pin 1 of this hat into the pin 1 of raspberry GPIO, just like the picture above.  Step 4. Power up Raspberry Pi Usage Now you can use the command to check whether the driver is installed successfully. 1 ./install.sh -l   If you want uninstall the driver you can use the command below: 1 sudo ./install.sh -u   Now let's see what the RTC module can do: Read hardware clock and print result 1 sudo hwclock -r   Set the system time from the hardware clock     1 sudo hwclock -s   Set the hardware clock from the current system time 1 sudo hwclock -w   More usage 1 hwclock --help   Tech Support Please do not hesitate to submit the issue into our forum                                                                        http://wiki.seeedstudio.com/Pi_RTC‐DS1307/ 12‐4‐18