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Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@allObjects
You have the power suply pin and you have the control/signal/data exchange pins. Latter are not a power draw issue as long as you do not add extra load - such as 'low' value resistors from display output pins, for example, MISO, to ground.
@Gordon thus mentioned that the control lines - (output) pins from Espruino to connected to display - should not power the display while power is off. Therfore, when powering up espruino and initializing AND before powering down the display,, these pins have all to be set input float ("input"). Only AFTER display is powered up, pins and communication - SPI - can be initialized and set.
Note that for proper working, signal lines do not need to go up to voltage supplied to display, but (certainly) should not be higher (otherwise they will power the display in one way or the other, or at least, try to...). The signal lines have only to reach a high or low as input specs with given supply voltage are specified, and that's true for both Espruino and display.