I²C
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I²C, alternatively known as I2C or IIC, is a synchronous, multi-controller/multi-target, single-ended, serial communication bus invented in 1982 by Philips Semiconductors. It is widely used for attaching lower-speed peripheral ICs to processors... Wikipedia
Number of devices: 128 devices
Bitrate: 0.1, 0.4, 1.0, 3.4 or 5.0 Mbit/s depending on mode
Data signal: Open-collector or open-drain
Designed: 1982; 42 years ago
Protocol: Serial, half-duplex
Width: 1-bit (SDA) with separate clock (SCL)