Wake ESP8266 by input signals during Deep Sleep the same way as Pin Change Interrupts

ESP8266 is very popular among IOT enthusiasts due to it’s builtin WiFi capabilities which keep our Fun Gadgets connected together. Normally it draws 215 mA current during data transmission and 0.9 mA are consumed during idle conditions when ESP8266 is not doing anything for us except keeping itself connected to our WiFi network. It’s Deep Sleep function is superb with 60 µA current consumption which is suitable in our Battery Powered Projects such as Weather Station, where it is required to take few readings during day or night and send them to the server and rest of time, ESP8266 keep itself under deep sleeps.

Sometimes, We require publishing some sort of output to our server and battery is only option to power our project. As ESP8266 does not support interrupts during deep sleep, how can We accomplish this task under this particular scenario?

Here, is a workaround, using couple of simple electronic components along with CH_PD, our ESP8266 will respond back to us even during deep sleep. Normally Reset, CH_PD, GPIO-0 and GPIO-2 are pulled up using 10 K resistors and GPIO-15 is pulled down the same way. But here we’ll pull CH_PD pin down using 10 K resistor.

Let’s suppose we have a Push Button attached to our Battery Powered ESP8266 and we want to publish it’s state to our server which is then proceeded to switch a relay connected to some other ESP8266.

NOTE: THIS METHOD WILL ONLY WORK WITH BARE ESP8266 MODEULE. IT WILL NOT WORK WITH ANY OF DEVELOPMENT BOARDS SUCH AS NODEMCU ETC.

Circuit Diagram:

Hardware Setup:

• Connect one side of Push Button to VCC and other side to a GPIO let’s suppose GPIO-4
• GPIO side of Push Button is pulled down using 10 K resistor
• Using a diode, GPIO is connected to CH_PD pin of ESP8266
• An other GPIO such as GPIO-12 is also connected to CH_PD using a diode in the same way.

When Push Button is pressed, It pulls CH_PD to HIGH which switches ESP8266 ON. In the mean time, other GPIO (GPIO-12, as supposed earlier) connected to CH_PD is defined as OUTPUT and switched to HIGH as early as possible in setup() function. ESP8266 boots up, waits for connection to server, publish the output and check for Push Button to be released. As soon as Button is released and information is published to server already, ESP8266 switches GPIO (GPIO-12, as supposed earlier) from HIGH to LOW and ESP8266 switches to OFF.

There are two Push Buttons attached to ESP8266 (at GPIO-5 and GPIO-4) in schematics shown above. ESP8266 responds to both of buttons in same manner identifies them individually. Here is an example sketch which uses ESPMetRED Library for communicating ESP8266 to Node-Red.

Example Sketch:

#include <ESPMetRED.h>

const char* MQTT_PUBLISH_TOPIC = "ESPBATTBUTTON/OUT";
const char* MQTT_SUBSCRIBE_TOPIC = "ESPBATTBUTTON/IN";
const char* CLIENT_ID = "ESPBATTBUTTON";
const char* WIFI_SSID = "Ahmed";
const char* WIFI_PASSWORD = "WiFI Password";
const char* MQTT_SERVER = "192.168.50.30";
const char* MQTT_USER = "pi";
const char* MQTT_PASSWORD = "MQTT Password"; 

IPAddress ip(192, 168, 50, 40);
IPAddress gateway(192, 168, 50, 1);
IPAddress subnet(255, 255, 255, 0);
IPAddress dns(192, 168, 50, 1);

ESPMetRED client(ip, gateway, subnet, dns); //starting library with fixed IP

int buttons[2] = {4, 5}; // Pins on which buttons are attached
int button;              // Variable to store the button which triggered the bootup
int wake = 12;           // Pin which is used to Keep ESP awake until job is finished

boolean published = false;
boolean notified = false;

void setup() {

// ESP Awake Pin, the pin which keeps CH_PD HIGH, a requirement for normal functioning of ESP8266
  pinMode(wake, OUTPUT);
  digitalWrite(wake, HIGH);


//Check which button was pressed

  for(int i=0; i<2; i++)
  {
    pinMode(buttons[i], INPUT);
    if(digitalRead(buttons[i]) == HIGH)
    {
      button = buttons[i];
      return; //Push Button identified, Leave the loop
    }
  }
}

void loop() {
  client.keepalive(); // Necessary for successful connection between server and client
  
  if((client.stMqTT()) && (!published)) // stMqTT() function returns the MQTT connection state
  {
    published = true;
    client.Publish("debug", client.JsonString(String(CLIENT_ID), String(button))); //Publish the data about Pushed Button
  }

  if((published) && (digitalRead(button) == HIGH)) // Check if button is released, a debounce step
  {
    if(!notified) // Notify the server that Button is not yet released
    {
      notified = true;
      client.Publish("debug", String(CLIENT_ID) + " [ESP Waiting Release of Button]");
    }
  }
  else if((published) && (digitalRead(button) == LOW)) //Push Button has released, Let's get switched OFF
  {
    client.Publish("debug", String(CLIENT_ID) + " [ESP's Going DOWN]");
    digitalWrite(wake, LOW); //Turns the ESP OFF
  }
}

Example Sketch Lite-I:

/*
	*	Two Push buttons are attached to GPIO 4 & 5
	*	GPIO 12 keeps the CH_PD HIGH
	*	ESP8266 goes to Sleep by switching GPIO 12 to LOW
*/

int buttons[2] = {4, 5}; // Pins on which buttons are attached
int button;              // Variable to store the button which triggered the bootup
int wake = 12;           // Pin which is used to Keep ESP awake until job is finished

void setup() {

// ESP Awake Pin, the pin which keeps CH_PD HIGH, a requirement for normal functioning of ESP8266
  pinMode(wake, OUTPUT);
  digitalWrite(wake, HIGH);


//Check which button was pressed

  for(int i=0; i<2; i++)
  {
    pinMode(buttons[i], INPUT);
    if(digitalRead(buttons[i]) == HIGH)
    {
      button = buttons[i];
      return; //Push Button identified, Leave the loop
    }
  }
  
  // do whatever you want before returning ESP8266 back to sleep
  
  digitalWrite(wake, LOW); //Turns the ESP OFF
}

void loop() {
  
}

Example Sketch Lite-II:

/*
	*	Push buttons is attached to GPIO 4
	*	GPIO 12 keeps the CH_PD HIGH
	*	ESP8266 goes to Sleep by switching GPIO 12 to LOW
*/

int button = 4; // Pin on which button is attached
int wake = 12;           // Pin which is used to Keep ESP awake until job is finished

void setup() {

// ESP Awake Pin, the pin which keeps CH_PD HIGH, a requirement for normal functioning of ESP8266
  pinMode(wake, OUTPUT);
  digitalWrite(wake, HIGH);

// do whatever you want before returning ESP8266 back to sleep
  
  digitalWrite(wake, LOW); //Turns the ESP OFF
}

void loop() {
  
}