I²C and SPI

Nowadays, at the low end of the transmission protocols, I²C (for ‘Inter-Integrated Circuit’, protocol) and SPI (for ‘Serial Peripheral Interface’) are to be found. Both protocols are well-suited for transmissions betwixt unified circuits, for slow transmission with onboard components. At the essence of these two popular protocols two major companies are found – Philips for I²C and Motorola for SPI – and two diverse histories about why, when and how the protocols were generated.
The I²C bus was developed in 1982; its authentic purpose was to supply an effortless way to link a CPU to peripherals chips in a TV set. Peripheral instruments in embedded systems are frequently connected to the microcontroller as memory-mapped I/O mechanisms. One straightforward way to do this is connecting the components to the microcontroller parallel address and data busses. This results in countless wiring on the PCB (printed circuit board) and supplementary ‘glue logic’ to decode the address bus on which all the peripherals are connected. To reserve microcontroller pins, further logic and make the PCBs simpler, in order words, to lower the expenditure.
SPI is a single-master communication protocol. This means that one fundamental device initiates all the communications with the servants.