|1||VBat||Focusing motor power|
|2||A_GND||Motor Ground (this contact pad is bigger then others)|
|3||VDD||Lens Difital power|
|4||Dout||SPI camera digital output|
|5||Din||SPI camera digital input|
|7||D_GND||Lens digital ground|
Connector view from camera side (face). Pads are counted from left to right, the bigger is second.
Three pins of Canon camera lens interface connector are for the power supply and four for a standard SPI serial interface (including digital ground). The communication is always initiated by the camera. The lens can send a busy state by pulling the Dclk pin down . The clock frequency is approx. 80kHz. One byte length, including the busy state from the lens, is 113us.
The camera reads the Din line state on rising edges of the Dclk line it generates. If there’s no ack from the lens, the camera will display an error after two or three tries.
The Dout line is held down when the camera generates the Dclk to read a byte from the lens on the Din line.