The SPI (Serial Peripheral Interface) protocol, or rather the SPI interface, was originally devised by Motorola (now Freescale) to support their microprocessors and microcontrollers. Unlike the I2C standard designed by Philips, the SPI interface has never been standardized; nevertheless, it has become a de-facto standard. National Semiconductor has developed a variant of the SPI under the name Microwire bus. The lack of official rules has led to the addition of many features and options that must be appropriately selected and set in order to allow proper communication between the various inte ...