If you use our stock firmware, you can just install using opkg
opkg update
opkg install kmod-i2c-gpio-custom
opkg install kmod-rtc-ds1307
If you want to compile your own firmware, choose these packages:
Kernel modules ---> I2C support ---> kmod-i2c-gpio-custom
Device Drivers ---> Real Time Clock ---> Dallas/Maxim DS1307/37/38/39/40, ST M41T00, EPSON RX-8025
The module should be very easy to install. You need to mount like in the picture. Most important, you need to solder GND, VCC, SDA and SCL.
The GPIO used for RTC is below:
SDA <--> GPIO1
SCL <--> GPIO17
Now you need in insert kernel modules and connect to the module
insmod /lib/modules/3.18.29/i2c-gpio-custom.ko bus0=0,1,17
echo ds1307 0x68 > /sys/bus/i2c/devices/i2c-0/new_device
To read the time from RTC module
hwclock -r
To sync the RTC module's time to mini router
hwclock -s
To write mini router's time to RTC module
hwclock -w