The I2C interface is very simple method of connecting multiple ICs together. Connect all of the SDA pins together and do the same from the SCL pins. Then add a pull-up resistor to the SDA line and the SCL line. If these resistors are missing, no communication will be possible.
The bus works by having one master and one or more slave devices. In theory upto 127 devices can be connected onto a single bus, each device must have a unique address. The address of each device is normally set by pulling one or more pins high or low. To understand this you will have to check with the device datasheets.
For the purpose of these pages, I have assembled a prototype board. The schematic diagram for this board is shown below.
