Deep Sleep

Browse source code on GitHub

Overview

The deep sleep mode of the ESP32 Series is a power saving mode that causes the CPU, majority of RAM, and digital peripherals that are clocked from APB_CLK to be powered off.

This sample shows how to set a wake up source, trigger deep sleep and then make use of that pre-configured wake up source to bring the system back again.

The following wake up sources are demonstrated in this example:

  1. Timer: An RTC timer that can be programmed to trigger a wake up after a preset time. This example will trigger a wake up every 20 seconds.

  2. EXT1: External wake up 1 is tied to multiple RTC GPIOs. This example uses GPIO2 and GPIO4 to trigger a wake up with any one of the two pins are HIGH.

  3. GPIO: Only supported by some Espressif SoCs, in the case of ESP32-C3 GPIOS0~5 can be used as wake-up sources.

The target SoC will always repeat the following: enable Timer as wake-up source, deep sleep for CONFIG_EXAMPLE_WAKEUP_TIME_SEC seconds, and wake up.

Requirements

This example should be able to run on any commonly available ESP32-DevKitC development board without any extra hardware if only Timer is used as wakeup source.

However, when EXT1 is enabled, GPIO2 and GPIO4 must be configured with a pull-down to avoid floating pins. This is typically done via the device tree (for example, using GPIO_PULL_DOWN). When triggering a wake-up, one or both pins must be driven high. Floating pins may trigger spurious wake-ups.

The GPIO pins and their electrical characteristics used for EXT1 or GPIO wake-up (such as pin number, pull configuration, and active level) are defined in the sample’s device tree overlay and can be modified for testing as needed.

Building, Flashing and Running

west build -b esp32_devkitc/esp32/procpu samples/boards/espressif/deep_sleep
west flash

Sample Output

ESP32 core output

With both wake up sources enabled, the console output will be as below. The reset reason message depends on the wake up source used. The console output sample below is for GPIO2.

*** Booting Zephyr OS build v4.3.0-4908-g23226d1f3a4e ***

Wake up from GPIO 2
Enabling timer wakeup, 5s
Powering off