EpdDeepSleep()

Syntax

EpdDeepSleep()

Overview

Places the driver IC and the EPD module into Deep Sleep mode.

Unlike a TFT display, an EPD panel needs no power at all to hold its current image — once pigment has settled into position, it stays there indefinitely with zero refresh current, which is the whole basis of e-paper's characteristic low power draw.
Deep Sleep exploits this directly: it powers down the driver IC's internal analog circuitry (charge pumps, VCOM generation, and similar) almost entirely, since none of it is needed to keep the already-displayed image visible — only to change it.
This makes Deep Sleep the correct state for a device that's finished updating the display and doesn't need to touch it again for a while, giving the lowest possible power draw between updates.

Note: To exit Deep Sleep, the driver IC needs a hardware reset. EpdSetUp() performs this by toggling the RESET pin, so calling it should bring the driver IC back out of Deep Sleep. In practice, this doesn't always work as expected — on some ICs, only a full power-off/power-on cycle reliably recovers the display, not a RESET-pin toggle alone. For more information read the EPD Displays topic.

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