I2C
A synchronous two-wire serial bus that connects a controller with addressed peripheral devices using shared clock and data lines.
Embedded-System Context
I2C shares clock and data lines among addressed devices. Pull-up resistance, bus capacitance, clock stretching, rise time, and arbitration affect both electrical and protocol behavior, and long wiring or heavy capacitance can lower the usable bus speed substantially.
Interface Boundary
I2C and SPI make different pin-count, topology, duplex, and throughput trade-offs. Neither is simply a universally faster or slower substitute for the other.