kamshory/rtcraspberrypi3bcentos7

RTC DS 1302 on Raspberry Pi 3 Model B under CentOS 7

Real Time Clock (RTC) is a time-keeping module that keep time running when Pi not connected to power supply and internet. In this section, we will use RTC DS 1302 with lithium battery.

We use Raspberry Pi 3 Model B and CentOS Userland 7 Minimal. We need C compiler to compile the program.

Compiling and Installing

To compile and install RTC DS 1302 module, run commands below.

yum group install -y "Development Tools"

cd /var

mkdir development

cd /var/development

rm -rf rtc-pi.c

curl --location https://github.com/kamshory/RTCRaspberryPi3BCentOS7/blob/master/rtc-pi.c > rtc-pi.c

cd /var/development

cc rtc-pi.c -o rtc-pi 

rm -rf /usr/sbin/rtc-pi

cp rtc-pi /usr/sbin/

echo -e '[Unit]' > /usr/lib/systemd/system/rtc.service

echo -e 'Description=rtc' >> /usr/lib/systemd/system/rtc.service

echo -e '' >> /usr/lib/systemd/system/rtc.service

echo -e '[Service]' >> /usr/lib/systemd/system/rtc.service

echo -e 'ExecStart=/usr/sbin/rtc-pi' >> /usr/lib/systemd/system/rtc.service

echo -e '' >> /usr/lib/systemd/system/rtc.service

echo -e '[Install]' >> /usr/lib/systemd/system/rtc.service

echo -e 'WantedBy=multi-user.target' >> /usr/lib/systemd/system/rtc.service

/usr/sbin/rtc-pi `date +"%Y%m%d%H%M%S"`

systemctl start rtc.service

systemctl enable rtc.service

reboot

rtcraspberrypi3bcentos7's Issues

Unable to set time on DS1302

No matter what i do I'm unable to set date on ds1302. I connected ds1302 and rpi3 like this:
ds1302 rpi3 ()
vcc -----------3.3 (1)
gnd-----------gnd (6)
clk------------GPIO21 (40)
dat-----------GPIO18 (12)
rst------------GPIO17 (11)
When i run sudo ./rtc-pi 20190131092503 i get correct time
Set UNIX timestamp to RTC: 1548923103
But when i read from ds1302 sudo ./rtc-pi
Read UNIX timestamp from RTC: 943916400
I get this date
Tue Nov 30 00:00:10 CET 1999
What am i doing wrong? Thanks.