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RTC for Raspberry Pi

Introduction

  This is RTC (real time clock) for Raspberry Pi, we know that almost all the RTC should be work on 5 volts, and Raspberry Pi’s GPIO serve for 3.3 volts, this RTC module is designed for Raspberry Pi, plug it to GPIO, can output 3.3V and 5V. Tip: if powered by GPIO, then do not power it with serial port, someone may make this mistake. There’s a TX (transmit) and a RX (receive), so, it’s convenient to connect to other device with serial port. RTC module can calculate time within ±2ppm, it shows date in this formation: week day month hour, minute, second, time zone year. When there’s a leap year, or days has changed in some month, it can adjust by itself. Chip DS1307 is build- in, DS1307 is a low power with highly accuracy real time clock. RTC module contains input port of battery, therefore, it still keeps accuracy of calculating time, when battery supply the power, static current is lower than 500nA.

 

Features

Chip: DS1307

Battery is CR1220

Could be controlled by shell script

Suit for GPIO of raspberry Pi

Could output square wave by program

RTC module can monitor the state of VCC, when detect power’s trouble, serve for reset output, and switch to backup power automatically.

 

Technical Datas

Interface:

Raspberry pi B 2*13 port

GPIO of Raspberry Pi 3

Space between interface: 2.54mm

 

Parameter

Operate voltage: 5V

Accuracy: ±2 ppm in 0 to +40℃

Valuable till 2100, leap year will get right compensation till 2100

Two calendar alarm clocks  

Operate temperatures: -10 to +85

 

Package

8 pins 64 mil so package

 

Application

Intelligent home

Remote message deal system

 

Usage

1.How to install it and how to get the right time?

1.install or renew i2c manage tool:

sudo apt-get install i2c-tools

2.Load i2c device

sudo modprobe i2c-dev

3.Scan i2c device

sudo i2cdetect -y -a 1

There’s a number 68 at the row of 60 and the column of 8

If it shows ”_” , the RTC module haven’t been detected or it is broken.

“_” means there’s no returned signal, UU means there’s returned signal but the corresponding address of device is occupied, the others returned value means the device has been detect and haven’t been occupied.

 

Trans to root identity

sudo su -

load i2c device

sudo modprobe i2c-dev

Indicate which driver should be used on device:

echo "ds1307 0x68"> /sys/class/i2c-adapter/i2c-1/new_device

Exit root

exit

See the time:

sudo hwclock -r            get date from RTC module

set system date as RTC module’s time

sudo hwcock -w           

however, the time may differ in several hours, it depends on your timezone.

Now, we get the real time on your location:

 

Open setting page

sudo raspi-config

 

Choose “Localisation Options”

Choose “Change Timezone”

Then choose the continent, country and city.

Here’s the date:

 

2.How to get the time whenever you open the Raspberry Pi?

Load in root

sudo su

Load setting page:

sudo raspi-config

choose “Interfacing Options”

Choose “I2C”

Select “yes”

 

sudo nano /etc/rc.local

Find the boot of it

Insert some code between “fi” and “exit 0”, press enter after “fi” then inset the following code:

echo "ds1307 0x68" > /sys/class/i2c-adapter/i2c-1/new_device

hwclock -s

tip: these codes are at the root situation

then Ctrl+O  to save

Ctrl+X  to exist

sudo reboot           reboot the system

 

start Raspberry Pi

input:

date

 

Detect the device:

I2cdetect -y -a 1

You’ll find this:

It used to be 68, and now, it shows UU, this means the device is detected and it’s working.

 


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