Enabling The I2C PortThe I2C port needs to be enabled in Rasbian before it can be used. See here.Checking For Connected DevicesAt the command prompt type one of these depending on whether you are using the I2C0 or I2C1 port:sudo i2cdetect -y 0//orsudo i2cdetect -y 1The 7 bit I2C address of all found devices will be shown (ignoring the R/W bit, so I2C address 0000 0110 is displayed as hex 03).

Source: Using the I2C Interface – Raspberry Pi Projects