SPI is bidirectional as is I2C. They both get used for similar applications, though SPI more often for anything needing a modicum of performance. Microwire or 1

SPI is bidirectional as is I2C. They both get used for similar applications, though SPI more often for anything needing a modicum of performance. Microwire or 1-wire should also be brought into the discussion to make it more complete.