ESP32 Deep Sleep : Push Button Message to IBM Watson IoT

We already demonstrated how to send message to IBM Watson IoT platform using ESP32 Arduino with just a button press. We have several non-IoT guides on pushbutton with Arduino including simple basic Arduino Blink LED With Pushbutton. Learning various logics with pushbutton will hugely help the beginners as pushbutton from the binary way of thought is a basic sensor to convey 0 or 1. Working with the sensors factually need minor modification from pushbutton projects. Those who are unused with IBM Watson IoT can read our getting started guide. Watson IoT is free tier is enough for this kind of projects. You will need to disable TLS/SSL security from IBM Watson IoT dashboard. Snippets for IBM Watson IoT is easy to convert to generic MQTT IoT projects. Many of the software parts IBM uses is Open Source.

It is better to go through our ESP32 Deep Sleep Guide and test the basic examples. To repeat the same basic theory: power saving is an important factor for the IoT applications and by saving power we can make one IoT project running with two AA batteries over a year. Deep Sleep turns off CPUs and most of the RAM and peripherals which are clocked from `APB_CLK`. The RTC controller, RTC peripherals and RTC memories are parts of the chip which can keep powered on. So, we must remember that both Wi-Fi and Bluetooth are powered off. However, the chip will store Wi-Fi and Bluetooth connection data in the RTC memory (`RTC_DATA_ATTR` attribute). If we want to store it into the RTC memory then we will define a global variable like `RTC_DATA_ATTR intboot count = 0;`.

This time, our code is an example of initiating Deep Sleep and waking up using a single push button. We talked about ESP32 wake-up external wake-up. We have two types of triggers – `ext0` when we want to wake-up the chip by one particular pin only and `ext1` –when we have several pins for the wake-up. Our example is with `ext0`.

We already have a dedicated repository for IBM Watson IoT for ESP32. This article’s code is also inside that repository.

There is no complex connection, circuit diagram for this project. Only adding a pushbutton to Pin 33 will work for this guide :

Next part is the code. We must inform you that our this coding is not fully “scientific”! We made the coding part easier yet fool proof by some cheating on our older code.

// this example uses one push button attached to pin 33
// push button attached to pin 33 sends message and puts it in to deep sleep
// again pushing the pushbutton attached to pin 33 it wakes up from sleep
// LED function kept as the this originated from my non deep-sleep code, it is not made working by code 

// written by Dr. Abhishek Ghosh, https://thecustomizewindows.com
// released under GNU GPL 3.0
// 

#define BUTTON_PIN_BITMASK 0x200000000 // 2^33 in hex; pin 33 for push button
RTC_DATA_ATTR int bootCount = 0;

const byte BUTTON=33; // boot button pin (built-in on ESP32)
const byte LED=2; // onboard LED (built-in on ESP32)

#include 
#include 
#include 
#include 
#define USE_SERIAL Serial 

#define FORCE_MODE 3
 
unsigned long buttonPushedMillis; // when button was released
unsigned long ledTurnedOnAt; // when led was turned on
unsigned long turnOnDelay = 20; // wait to turn on LED
unsigned long turnOffDelay = 5000; // turn off LED after this time
bool ledReady = false; // flag for when button is let go
bool ledState = false; // for LED is on or not.


const char* ssid = "fill up";
const char* password = "fill up";

#define ORG "write here" // change
#define DEVICE_TYPE "change" // change
#define DEVICE_ID "change" // change
#define TOKEN "copy-paste" // change
#define EVENT "myEvent" // example

// <------- CHANGE PARAMETERS ABOVE THIS LINE ------------>

String urlPath = "/api/v0002/device/types/" DEVICE_TYPE "/devices/" DEVICE_ID "/events/" EVENT;
String urlHost = ORG ".messaging.internetofthings.ibmcloud.com";
int urlPort = 8883;
String authHeader;

void deep_sleep() {
    printf("Sleep at %d ms\n\n", millis());
    delay(20);
    // esp_sleep_enable_timer_wakeup(20000 * 1000); // Deep-Sleep time in microseconds
    esp_sleep_enable_ext0_wakeup(GPIO_NUM_33,1); //1 = High, 0 = Low 
    esp_deep_sleep_start();
    // Serial.println("This will never be printed");

}
 
void setup() {
 Serial.begin(115200); Serial.println();
 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));
 pinMode(BUTTON, INPUT_PULLUP);
 pinMode(LED, OUTPUT);
 digitalWrite(LED, LOW);

initWifi();
authHeader = "Authorization: Basic " + base64::encode("use-token-auth:" TOKEN) + "\r\n";
doWiFiClientSecure();
loop();
}

void doWiFiClientSecure() {
 WiFiClientSecure client;
 Serial.print("connect: "); Serial.println(urlHost);
 while ( ! client.connect(urlHost.c_str(), urlPort)) {
    Serial.print(".");
 }
 Serial.println("Connected");
 String postData = String("{  \"d\": {\"aMessage\": \"") + millis()/1000 + "\"}  }";
 String msg = "POST " + urlPath + " HTTP/1.1\r\n"
                "Host: " + urlHost + "\r\n"
                "" + authHeader + ""
                "Content-Type: application/json\r\n"
                "Content-Length: " + postData.length() + "\r\n"
                "\r\n" + postData;
                
 client.print(msg);
 Serial.print(msg);

 Serial.print("\n*** Request sent, receiving response...");
 while (!!!client.available()) {
    delay(50);
 Serial.print(".");
  }
  
Serial.println();
Serial.println("Got response");  
  while(client.available()){
  Serial.write(client.read());
  }
Serial.println(); Serial.println("closing connection");
  client.stop();
}

void initWifi() {
  Serial.print("Connecting to: "); Serial.print(WiFi.SSID());
  WiFi.mode(WIFI_STA);   
  WiFi.begin(ssid, password);  
  while (WiFi.status() != WL_CONNECTED) {
     delay(250);
     Serial.print(".");
  }
  
  Serial.println("");
  Serial.print("WiFi connected, IP address: "); Serial.println(WiFi.localIP());

}

void loop() {
 // get the time at the start of this loop()
 unsigned long currentMillis = millis(); 
 // check the button
 if (digitalRead(BUTTON) == LOW) {
  // update the time when button was pushed
  buttonPushedMillis = currentMillis;
  ledReady = true;
 }
  
 // make sure this code isn't checked until after button has been let go
 if (ledReady) {
   //this is typical millis code here:
   if ((unsigned long)(currentMillis - buttonPushedMillis) >= turnOnDelay) {
     // okay, enough time has passed since the button was let go.
     digitalWrite(LED, HIGH);
     doWiFiClientSecure();
     // setup our next "state"
     ledState = true;
     // save when the LED turned on
     ledTurnedOnAt = currentMillis;
     // wait for next button press
     ledReady = false;
   }
 }
  
 // see if we are watching for the time to turn off LED
 if (ledState) {
   // okay, led on, check for now long
   if ((unsigned long)(currentMillis - ledTurnedOnAt) >= turnOffDelay) {
     ledState = false;
     digitalWrite(LED, LOW); 
   }
 }
deep_sleep();               
}

We have tested the above thing and it is working except the LED blink part (it is not fixed yet). Basically within `void setup() {`, we are calling the other functions. From coding point of view, the way we achieved is dirty. We did it for faster achieving the result using our old code to send message to IBM Watson IoT. Deep Sleep is stopping the `void loop()` :

...

void setup() {
…

initWifi();
authHeader = "Authorization: Basic " + base64::encode("use-token-auth:" TOKEN) + "\r\n";
doWiFiClientSecure();
loop();
}
...

It does the job but the logical steps are better to be construct in clean way. If you are student, you should re-write it in clean manner for your engineering project.