This is the third in our series about using shift-out and unused analog lines to drive SPI displays. The primary reason to use this method is to save power in data logging applications that need to run for years at a time. When you drive the pin-power line down the screen is completely disabled and draws no current.

https://thecavepearlproject.org/2018/10/17/tutorial-adding-a-ssd1306-oled-screen-to-your-arduino-logger/