The CP2120 compact SPI-to-I2C bridge and general purpose port expander device can be easily added to a system to solve interface compatibility problems and add more GPIO when required. The chip includes a 4-wire slave SPI bus, bridge control logic, a bidirectional I2C bus interface and eight general-purpose input/output (I/O) pins. An SPI master communicates with other I2C devices by instructing the CP2120 to send and receive I2C data traffic using the simple command set. The CP2120 can act as a master-transmitter and a master-receiver on the I2C bus. All I2C timing, addressing and arbitration is handled by the CP2120.