from now broken freehabr website translated from russian: Preamble Somehow, my colleagues and I needed to control the Canon EF 200 lens without a camera (and then the Canon EF 85 also appeared). The task at first glance is simple, but in reality everything turned out to be not so simple. After a long search on the Internet, only a control ring offered for 1 thousand “green” was found, connected to a computer via RS-232 (naturally, this was immediately rejected); pinout of the connector with which the lens is connected to the camera; as well as small hints that the SPI interface is used to control the lens. SPI is so SPI. Of the available ones, a microcontroller with an “on-board” SPI (PIC16F873a) was chosen, and on its basis, control electronics were assembled on the breadboard knee (an RS-232 level converter, the microcontroller itself and a 4 MHz quartz resonator - there was no other at hand). Other colleagues begged for a digital oscilloscope with the ability to record measure...