/*

Simple Deep Sleep with Timer Wake Up

=====================================

ESP32 offers a deep sleep mode for effective power

saving as power is an important factor for IoT

applications. In this mode CPUs, most of the RAM,

and all the digital peripherals which are clocked

from APB_CLK are powered off. The only parts of

the chip which can still be powered on are:

RTC controller, RTC peripherals ,and RTC memories



This code displays the most basic deep sleep with

a timer to wake it up and how to store data in

RTC memory to use it over reboots



This code is under Public Domain License.



Author:

Pranav Cherukupalli <cherukupallip@gmail.com>

*/



#define uS_TO_S_FACTOR 1000000ULL /* Conversion factor for micro seconds to seconds */

#define TIME_TO_SLEEP 5 /* Time ESP32 will go to sleep (in seconds) */



RTC_DATA_ATTR int bootCount = 0;



/*

Method to print the reason by which ESP32

has been awaken from sleep

*/

void print_wakeup_reason(){

esp_sleep_wakeup_cause_t wakeup_reason;



wakeup_reason = esp_sleep_get_wakeup_cause();



switch(wakeup_reason)

{

case ESP_SLEEP_WAKEUP_EXT0 : Serial.println("Wakeup caused by external signal using RTC_IO"); break;

case ESP_SLEEP_WAKEUP_EXT1 : Serial.println("Wakeup caused by external signal using RTC_CNTL"); break;

case ESP_SLEEP_WAKEUP_TIMER : Serial.println("Wakeup caused by timer"); break;

case ESP_SLEEP_WAKEUP_TOUCHPAD : Serial.println("Wakeup caused by touchpad"); break;

case ESP_SLEEP_WAKEUP_ULP : Serial.println("Wakeup caused by ULP program"); break;

default : Serial.printf("Wakeup was not caused by deep sleep: %d\n",wakeup_reason); break;

}

}



void setup(){

Serial.begin(115200);

delay(1000); //Take some time to open up the Serial Monitor



//Increment boot number and print it every reboot

++bootCount;

Serial.println("Boot number: " + String(bootCount));



//Print the wakeup reason for ESP32

print_wakeup_reason();



/*

First we configure the wake up source

We set our ESP32 to wake up every 5 seconds

*/

esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR);

Serial.println("Setup ESP32 to sleep for every " + String(TIME_TO_SLEEP) +

" Seconds");



/*

Next we decide what all peripherals to shut down/keep on

By default, ESP32 will automatically power down the peripherals

not needed by the wakeup source, but if you want to be a poweruser

this is for you. Read in detail at the API docs

http://esp-idf.readthedocs.io/en/latest/api-reference/system/deep_sleep.html

Left the line commented as an example of how to configure peripherals.

The line below turns off all RTC peripherals in deep sleep.

*/

//esp_deep_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_OFF);

//Serial.println("Configured all RTC Peripherals to be powered down in sleep");



/*

Now that we have setup a wake cause and if needed setup the

peripherals state in deep sleep, we can now start going to

deep sleep.

In the case that no wake up sources were provided but deep

sleep was started, it will sleep forever unless hardware

reset occurs.

*/

Serial.println("Going to sleep now");

Serial.flush(); 

esp_deep_sleep_start();

Serial.println("This will never be printed");

}



void loop(){

//This is not going to be called

}