Raspberry Pi Real Time Clock Module

Instructions for Raspbian 'Wheezy', early versions (not 'Jessie')

Setting up the RTC

If you have a Raspberry Pi 2 or firmware later than 29th Jan 2015, you will need to add the following line to your CONFIG.TXT file:

dtparam=i2c_arm=on

To enable support for the RTC in Raspbian 'Wheezy' (2012-10-28 or later), the following lines need to be added to /etc/rc.local above the exit0 line:

modprobe i2c-bcm2708
echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device
modprobe rtc-ds1307
hwclock -s

Setting up the Temperature Sensor

To enable support for the temperature sensor in Raspian, log in as your usual username and follow the steps below:

1. Enable I2C in modprobe: (not necessary on Raspberry Pi 2 or with firmware later than 29th Jan 2015)
   Edit the file '/etc/modprobe.d/raspi-blacklist.conf' and comment out the two lines:
   blacklist spi-bcm2708
blacklist i2c-bcm2708
2. Load the i2c kernel drivers:
   sudo modprobe i2c-dev
3. Check that the i2c devices have appeared in /dev:
   ls -l /dev/i2c*
   You should see the items '/dev/i2c-0' and/or '/dev/i2c-1' are listed.
4. Install the i2c tool chain: (This may not necessary on Raspberry Pi 2 or with firmware later than 29th Jan 2015)
   (You will need to be connected to the internet for this step)
   sudo apt-get install i2c-tools
5. Add your user to the i2c usergroup:
   This is so you don't need to use sudo to interact with the i2c device.
   sudo usermod -aG i2c yourusername
6. Talking to the I2C device:
   On Mk.1 boards: i2cdetect -y 0
   On Mk 2/B+/Compute Module boards: i2cdetect -y 1
   You should see devices at 0x4F & 0x68 - these are the temperature sensor and RTC chip respectively.
7. Read from the temp sensor:
   On Mk.1 boards: echo $(($(i2cget -y 0 0x4F)))
   On Mk.2/B+/Compute Module boards: echo $(($(i2cget -y 1 0x4F)))
   Which should return an integer, eg. 32 = 32C