Independent of this development in computer science, the progress in microelectronics brought forward many different integrated controllers, and new interfaces were needed to interconnect the integrated circuits in an efficient and cheap way.
Consequently, electrical engineers—without the knowledge of the ISO/OSI model or similar architectures—defined simple buses such as the I2C. Being interfaces rather than full-fledged
bus systems, they have very simple protocols, but they were (and still are) widely used in electronic systems.