The RTC Pi is very useful for standalone projects where your Raspberry Pi will not have a network connection and therefore no way to retrieve the current date and time from the internet.
A mounting hole is provided so you can securely bolt the RTC Pi to your Raspberry Pi with our mounting kit (sold separately).
The RTC Pi can also be used on Arduino boards when connected via the I2C bus.
The i2c address for the DS1307 RTC is 0x68. This board is not compatible with the ADC Pi V1 board but is compatible with the Delta Sigma Pi and ADC Pi V2 when alternative i2c addresses are used.
Warning: Do not connect the RTC Pi to your Raspberry Pi when the power is connected without a CR2032 battery installed. This can cause damage to the DS1307 RTC chip.
The RTC Pi uses a CR2032 button battery (battery not included).
Due to shipping restrictions we are no longer allowed to ship the RTC Pi with a battery.
Click to download schematic PDF.
Click image to enlarge
How to set and read the time
The RTC Pi requires a Linux kernel with i2c drivers such as the Occidentalis system image from http://learn.adafruit.com/adafruit-raspberry-pi-educational-linux-distro/overview which has i2c enabled.
To access the RTC Pi from your Raspberry Pi:
Boot the Pi from that image and execute these commands as root / su user:
First you need to register the DS1307 RTC chip with the I2C address of 0x68:
For Revision One boards use:
echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-0/new_device
For Revision Two boards use:
echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device
To set the RTC Pi clock with the current system time:
View the current date and time stored in the RTC Pi:
Set the Linux system time to the value in the RTC Pi:
To set the RTC Pi with a custom time:
hwclock --set --date="2012-12-25 06:00:12" --utc
Battery Notes: We have had reports that some brands of button cells do not make a reliable connection when fully inserted into the battery holder on the version 1 RTC Pi boards. Moving the battery out by 3-5mm solves this problem.
The schematic for the RTC Pi version 1 can be found here.