Wires (Two)

• SDA (serial data)
• SCL (serial clock)

Multiple masters and multiple slaves. All devices are wired together (that is the SDA and SCL lines for each device are connected). Any device an initiate communication with any other.

Compared to

Serial (RS232)

• Tx (transmit data)
• Rx (receive data)

The Tx wire of one end is wired to the Rx wire of the other end, and vice-versa.

### Note On the Arduino Uno the following pins are used for RS232 serial and USB:

• 0: Rx (incoming data)
• 1: Tx (outgoing data)