RasClock is a highly accurate real-time clock that plugs directly into the Raspberry Pi and includes a battery backup. The module is installed directly into the GPIO header pins with no wiring or soldering. It uses the 3.3V, GND SDA and SCL pins. The module stays within the outline of the Raspberry Pi and sits lower than video output so can be easilly installed within most cases.
Updated V4.2 - The Rasclock now features an 8 Pin Header input, so boards can be stacked on top!
RasClock utilises the highly accurate NXP PCF2127AT chip and features:
Very accurate timekeeping (typically ±3ppm or <2 minutes deviation per year).
Integrated crystal that compensates for temperature and age.
A 36mA 3V battery will keep the time for around two years if the device isn't used and considerably longer if it is.
Fits inside most cases easilly inclusing the ModMyPi Raspberry Pi Case, PiBow's and Multicomp Cases.
Why do I need a Real Time Clock for my Raspberry Pi?
The Raspberry Pi is an ultra-small and ultra-low cost computer. In order to achieve this size and price, several non-essential items usually found on a computer had to be omitted. Laptops and computers keep time when the power is off by using a pre-installed, battery powered 'Real Time Clock' (RTC). However, this Real Time Clock module is not included with the Raspberry Pi. To keep time, the Raspberry Pi updates the date and time automatically over the internet via Ethernet or WiFi.
The Raspberry Pi will simply revert back to the standard date and time settings (usually 30 November 1999) when the network connection is removed. So, for projects which have no internet connection, you may want to add a low cost battery powered RTC to help your Pi keep time!
The RasClock has been specifically designed for use with the Raspberry Pi and, unlike other RTC's available, can plug directly in to the Raspberry Pi's GPIO Ports.
Your info states that the new v4.0 has an 8-pin input so that it can be stacked. How does this work with the 40-pin GPIO.? Ho can I plug the RTC into the Pi and then stack other HATs on top if the RTC doesn't have a full 40-pin female header on the underside and a 40-pin male header on the top side? Cheers.
The 8 pin header simply allows you to use jumper wires to connect another breakoutboard that shares the I2C pins. If you want to stack this board with a HAT then the HAT will need extra long pins so you can place the RTC on top.