Deep sleep

The deep_sleep component powers the device down between runs. On ESP32, ESP8266 and BK72xx, a wake from deep sleep restarts the firmware from the beginning, so setup() runs again just as it does after a power cycle, a reset or an OTA update.

Some components can do less work on a wake. For example, a chip next to the microcontroller may keep its own state while the microcontroller sleeps, and that state can only change with new firmware, so there is nothing to check again. Such a component can ask whether this boot is a wake from deep sleep:

#ifdef USE_DEEP_SLEEP
#include "esphome/components/deep_sleep/deep_sleep_component.h"
#endif

void MyComponent::setup() {
#ifdef USE_DEEP_SLEEP
  if (deep_sleep::woke_from_deep_sleep()) {
    this->resume_();
    return;
  }
#endif
  this->full_init_();
}

Without deep_sleep in the configuration the device never wakes from deep sleep, so the code outside the #ifdef treats every boot as a normal boot. Do not add deep_sleep to DEPENDENCIES or AUTO_LOAD only to use this check.

deep_sleep::get_wakeup_cause() returns the reason as a WakeupCause value: WAKEUP_CAUSE_TIMER, WAKEUP_CAUSE_GPIO, WAKEUP_CAUSE_TOUCH, WAKEUP_CAUSE_UNKNOWN, or WAKEUP_CAUSE_NONE for a boot that was not a wake. woke_from_deep_sleep() is the same as get_wakeup_cause() != WAKEUP_CAUSE_NONE. Both are available whenever deep_sleep is configured, with or without an on_wake automation.

On nRF52 (Zephyr), a wake from System OFF is not yet told apart from a reset, so both report a normal boot. Code that uses them must still work correctly when a wake is reported as a normal boot.