* Connect the '''SDA''' pin to the I2C data SDA pin on your Arduino. On an UNO & '328 based Arduino, this is also known as '''A4''', on a Mega it is also known as digital 20 and on a Leonardo/Micro, digital 2 | * Connect the '''SDA''' pin to the I2C data SDA pin on your Arduino. On an UNO & '328 based Arduino, this is also known as '''A4''', on a Mega it is also known as digital 20 and on a Leonardo/Micro, digital 2 |