Deep sleep

Using deep sleep on Inkplate 2 is key to writing a sketch that maximizes battery efficiency. Since the e-Paper display does not require power to retain the displayed image, Inkplate 2 can use little to no current while in deep sleep mode, so a sketch can run for months on battery.

ℹ️

If all peripherals are in sleep mode, deep sleep current will be around 20-30µA

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Simple deep sleep

See how deep sleep works with the example below:

#define uS_TO_S_FACTOR 1000000 // Conversion factor for micro seconds to seconds
#define TIME_TO_SLEEP  20 //How long ESP32 will be in deep sleep (in seconds)
void setup(){
    //your code
    ///...
    esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR); //Activate wake-up timer -- wake up after 20s here
    esp_deep_sleep_start(); //Put ESP32 into deep sleep. Program stops here.
}

esp_sleep_enable_timer_wakeup()

This function enables wakeup by timer.

Returns type: int

Returns value: Returns ESP error code

Function parameters:

Type	Name	Description
uint64_t	time_in_us	Wakeup time in microseconds.

esp_deep_sleep_start()

This function enters deep sleep with the configured wakeup options.

Returns type: None

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Wake on button press

To wake on the button press of the Wake button, use the ESP32 function esp_sleep_enable_ext0_wakeup() before putting it to sleep.

// Go to sleep for TIME_TO_SLEEP seconds
esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR);

// Enable wakeup from deep sleep on gpio 36 (wake button)
esp_sleep_enable_ext0_wakeup(GPIO_NUM_36, LOW);

// Go to sleep
esp_deep_sleep_start();

esp_sleep_enable_ext0_wakeup()

This function uses the external wakeup feature of the RTC_IO peripheral.

Returns type: int

Returns value: Returns ESP error constant

Function parameters:

Type	Name	Description
gpio_num_t	gpio_num	GPIO number used as wakeup source. Only GPIOs that have RTC functionality can be used.
int	level	Input level which will trigger wakeup.

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Full examples

Check out the full examples on this page, along with many more usage options below:

Inkplate2_Simple_Deep_Sleep.ino

This example shows you how to use the low power functionality of the Inkplate board.

Inkplate2_RTC_Alarm_With_Deep_Sleep.ino

This example demonstrates how to use the RTC alarm interrupt with deep sleep.