Loading... Please wait...

RasClock - Raspberry Pi Real Time Clock Module

  • Image 1
  • Image 2
Current Stock:
Out of stock

Sorry but this item is currently unavailable.

Please check back at a later stage.

Product Description

RasClock v5.0 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.


RasClock uses one of the following chips:


RasClock features:

  • Very accurate timekeeping (typically ±3ppm or <2 minutes deviation per year).
  • Integrated crystal that compensates for temperature and age.
  • The supplied 36mA 3V battery will keep the time for around two years if the device isn't used and considerably longer if it is.
  • Coin Battery Included!
  • 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.

Complete installation and set up instructions can be found at http://afterthoughtsoftware.com/products/rasclock

Additional tutorial can be found at https://www.modmypi.com/blog/installing-the-rasclock-raspberry-pi-real-time-clock

Set up is easy, simply follow the guide Outlined in the ModMyPi Raspberry Pi Tutorial Here!


How to check what version of hardware and software running on your Raspberry Pi:


pi@raspberrypi:/$ sudo bash
pi@raspberrypi:/# cat /proc/cpuinfo
Processor       : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS        : 697.95
Features        : swp half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xb76
CPU revision    : 7

Hardware        : BCM2708
Revision        : 0003
Serial          : 00000000c0ae10d9

root@raspberrypi:/# cat /etc/debian_version

root@raspberrypi:/# uname -or
3.6.11+ GNU/Linux


How to configure RTC module and remove fake-hwclock (when using wheezy 3.6.11):

sudo bash

apt-get remove fake-hwclock
rm /etc/cron.hourly/fake-hwclock
update-rc.d -f fake-hwclock remove
rm /etc/init.d/fake-hwclock


wget http://afterthoughtsoftware.com/files/linux-image-3.6.11-atsw-rtc_1.0_armhf.de
dpkg -i linux-image-3.6.11-atsw-rtc_1.0_armhf.deb
cp /boot/vmlinuz-3.6.11-atsw-rtc+ /boot/kernel.img

echo "i2c-bcm2708" >> /etc/modules
echo "rtc-pcf2127a" >> /etc/modules

Add the following to /etc/rc.local before "exit 0":

# Referring to
# http://www.raspberrypi-spy.co....
# to get the RasPi board version:
REV=$(cat /proc/cpuinfo|grep Revision)
# Extract revision
REV=${REV##*: }
# Make it readable as hex
# Convert hex to dec
if [ $REV -lt 4 ]
  echo pcf2127a 0x51 > /sys/class/i2c-adapter/i2c-0/new_device
  echo setting rtc to i2c-0
  echo pcf2127a 0x51 > /sys/class/i2c-adapter/i2c-1/new_device
  echo setting rtc to i2c-1
( sleep 2; hwclock -s ) &


Then reboot:


Console should show similar to:

[   32.897890] rtc-pcf2127a 0-0051: chip found
[   32.899695] rtc-pcf2127a 0-0051: rtc core: registered rtc-pcf2127a as rtc0
[   32.899757] i2c i2c-0: new_device: Instantiated device pcf2127a at 0x51

Then later nearer the login prompt:

Board revision: X
setting rtc to i2c-X


Log back in and verify date is correct:



Set hardware clock to current system time:

sudo hwclock -w



Verify hardware clock is set correctly:


sudo hwclock -r




Find Similar Products by Category

Write your own product review

Product Reviews

Showing reviews 1-2 of 7 | Next

  1. RasClock works as expected 5 Star Review

    Posted by on 22nd Dec 2016

    I had no issues with the RasClock. It fits in the standard case nicely with plenty of clearance.

    It connects to the GPIO header so you cannot use it with other PI caps.

  2. Plugged it in, set it up, works. 4 Star Review

    Posted by on 26th Oct 2015

    RasClock works as described! I am using it with Falcon Player so the system knows when to fire-off events and, so far in my testing, it works as it should.

    My only gripe is that since the chip/battery are mounted on the bottom, they are sort of clock to the heatsink of one of the rPi chips.

Showing reviews 1-2 of 7 | Next

You Recently Viewed...