[[File:Pi4-V3-HAT.png|800px]]
'''Q: How to enable RTC?'''
A: Firstly, insert the C1220 button battery.
run the following command:
rw
sudo nano /boot/config.txt
#Then change the line: '''dtoverlay=i2c-rtc,pcf8563''' to '''dtoverlay=i2c-rtc,ds1307'''
#Test RTC
#Display the current time of the Raspberry Pi
date
#Write the time of Raspberry Pi to DS1307
reboot before next step
sudo hwclock -w
#Read the time of DS1307
sudo hwclock -r
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