Raspberry Pi IoT Gateway Programming – Sample Programs

Brief:

Basic ESP32 COAP Example

• ESp32 wifi module uses provided SSID and password, tries to connect wifi.once connected to wifi, ipadress and SSID is printed on serial monitor.
• Client sends request to controla state of led i.e Status of led to turn ON or OFF the led
• Server upon reciving request, turn ON/OFF led and response the state of led.

Source Code:

 /*-------------------------------------------------------------------------------------------------------------------
 * Author          : Emertxe (http://www.emertxe.com) 
 * Date            : Fri 13 Agust  2021 16:00:04 IST
 * File            : esp32_coap.ino
 * Title           : Program on demonstrating COAP based server client communication 
 * Description     : Basic ESP32 COAP example
 *                   ESp32 wifi module uses provided SSID and password, tries to connect wifi.once connected to wifi,
 *                   ipadress and SSID is printed on serial monitor.
 *                   Client sends request to controla state of led i.e Status of led to turn ON or OFF the led
 *                   Server upon reciving request, turn ON/OFF led and response the state of led. 
 * Installation    : Libraries to be installed:
 *                   goto Tools -> Manage Libraries -> search for COAP_simple_libray and install COAP_simple_library
 * Execution Steps : if you change LED, req/res test with coap-client(libcoap), run following.
 *                   coap-client -m get coap://(arduino ip addr)/light
 *                   coap-client -e 1 -m put coap://(arduino ip addr)/light
 *                   coap-client -e 0 -m put coap://(arduino ip addr)/light
 *------------------------------------------------------------------------------------------------------------------*/

#include 
#include 
#include 

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

// CoAP client response callback
void callback_response(CoapPacket &packet, IPAddress ip, int port);

// CoAP server endpoint url callback
void callback_light(CoapPacket &packet, IPAddress ip, int port);

// UDP and CoAP class
WiFiUDP udp;
Coap coap(udp);

// LED STATE
bool LEDSTATE;
int led = LED_BUILTIN;

// CoAP server endpoint URL
void callback_light(CoapPacket &packet, IPAddress ip, int port) {
  Serial.println("[Light] ON/OFF");
  
  // send response
  char p[packet.payloadlen + 1];
  memcpy(p, packet.payload, packet.payloadlen);
  p[packet.payloadlen] = NULL;
  
  String message(p);

  if (message.equals("0"))
    LEDSTATE = false;
  else if(message.equals("1"))
    LEDSTATE = true;
      
  if (LEDSTATE) {
    digitalWrite(led, HIGH) ; 
    coap.sendResponse(ip, port, packet.messageid, "1");
  } else { 
    digitalWrite(led, LOW) ; 
    coap.sendResponse(ip, port, packet.messageid, "0");
  }
}

// CoAP client response callback
void callback_response(CoapPacket &packet, IPAddress ip, int port) {
  Serial.println("[Coap Response got]");
  
  char p[packet.payloadlen + 1];
  memcpy(p, packet.payload, packet.payloadlen);
  p[packet.payloadlen] = NULL;
  
  Serial.println(p);
}

void setup() {
  Serial.begin(115200);

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
      delay(500);
      Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());

  // LED State
  pinMode(led, OUTPUT);
  digitalWrite(led, HIGH);
  LEDSTATE = true;
  
  
  Serial.println("Setup Callback Light");
  coap.server(callback_light, "light");

  // client response callback.
  // this endpoint is single callback.
  Serial.println("Setup Response Callback");
  coap.response(callback_response);

  // start coap server/client
  coap.start();
}

void loop() {
  delay(1000);
  coap.loop();
}

Raspberry pi sample program output:

Brief:

Source Code:

/*---------------------------------------------------------------------------------------------------------------------------
*Author          : Emertxe (http://www.emertxe.com) 
*Date            : Fri 13 Agust  2021 16:00:04 IST
*File            : HelloServer.ino
*Title           : Program on demonstrating HTTP based server client communication 
*Description     : ESp32 wifi module uses provided SSID and password, tries to connect wifi.once connected to wifi,ipadress
*                  and SSID is printed on serial monitor.Browser will act like client.ESP32 act as server, server responds 
*                  with "hello from esp2866" on reciving rrequest for connection. 
*Installation    : Libraries to be installed:
*                  New version of arduino has all library installed.
*Execution Steps : Copy ip adress from serial terminal.
*                  Paste ip adress on the browser(to get hello from server). 
*----------------------------------------------------------------------------------------------------------------------------*/


#include 
#include 
#include 
#include 

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

// TCP server at port 80 will respond to HTTP requests
WebServer server(80);

const int led = LED_BUILTIN;

//response "hello sserver upon connection"
void handleRoot() 
{
  digitalWrite(led, 1);
  server.send(200, "text/plain", "hello from esp8266!");
  digitalWrite(led, 0);
}

// handle request if path arguments are not matching
void handleNotFound() 
{
  digitalWrite(led, 1);
  String message = "File Not Found\n\n";
  message += "URI: ";
  message += server.uri();
  message += "\nMethod: ";
  message += (server.method() == HTTP_GET) ? "GET" : "POST";
  message += "\nArguments: ";
  message += server.args();
  message += "\n";
  for (uint8_t i = 0; i < server.args(); i++)
  {
    message += " " + server.argName(i) + ": " + server.arg(i) + "\n";
  }
  server.send(404, "text/plain", message);
  digitalWrite(led, 0);
}

void setup(void) 
{
  pinMode(led, OUTPUT);
  digitalWrite(led, 0);
  Serial.begin(115200);
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  Serial.println("");

  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) 
  {
    delay(500);
    Serial.print(".");
  }
  //once connected to wifi print ipadress
  Serial.println("");
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());

  if (MDNS.begin("esp32")) 
  {
    Serial.println("MDNS responder started");
  }

  server.on("/", handleRoot);

  server.on("/inline", []() 
  {
    server.send(200, "text/plain", "this works as well");
  });

  server.onNotFound(handleNotFound);

  server.begin();
  Serial.println("HTTP server started");
}

void loop(void) 
{
  server.handleClient();
}

Example output:

Brief:

Source Code:

/*-----------------------------------------------------------------------------------------------------------------------------
*Author            : Emertxe (http://www.emertxe.com) 
*Date              : Fri 13 Agust  2021 16:00:04 IST
*File              : HelloServer.ino
*Title             : Program on demonstrating HTTP based server client communication 
*Description       : Basic ESP32 HTTP example
*                    ESp32 wifi module uses provided SSID and password, tries to connect wifi.once connected to wifi,
*                    ipadress and SSID is printed on serial monitor.
*                    Browser will act like client.
*                    ESP32 act as server, server responds with "hello from esp2866" on reciving rrequest for connection. 
*                    Server responds with turning ON and OFF led, on reciving request ON or OFF as path arguments from client.
*Istallation       : Libraries to be installed:
*                    New version of arduino has all library installed
*Execution steps   : Copy ip adress from serial terminal.
*                    Paste ip adress on the browser(to get hello from server). 
*                    Paste ip adreess/led/ON or OFF (to control led status on esp32)
------------------------------------------------------------------------------------------------------------------------------*/


#include 
#include 
#include 
#include 

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

// TCP server at port 80 will respond to HTTP requests
WebServer server(80);

void setup(void) {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  Serial.println("");

  pinMode(LED_BUILTIN, OUTPUT);

  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
//multicast domain name system
  if (MDNS.begin("esp32")) {
    Serial.println("MDNS responder started");
  }

  server.on("/", []() {
    server.send(200, "text/plain", "hello from esp32!");
  });


// to obtain led status from request path agruments
  server.on("/led/{}", []() {
    String led_status = server.pathArg(0);

    int status = led_status == "ON" ? 1 : 0;
    digitalWrite(LED_BUILTIN, status);
    
    server.send(200, "text/plain", "LED: '" + led_status + "'");
  });
  
  server.on("/users/{}", []() {
    String user = server.pathArg(0);
    server.send(200, "text/plain", "User: '" + user + "'");
  });
  
  server.on("/users/{}/devices/{}", []() {
    String user = server.pathArg(0);
    String device = server.pathArg(1);
    server.send(200, "text/plain", "User: '" + user + "' and Device: '" + device + "'");
  });

  server.begin();
  Serial.println("HTTP server started");
}

void loop(void) 
{
  server.handleClient();
}

Raspberry pi sample program output:

/*------------------------------------------------------------------------------------------------------------------------------
*Author            : Emertxe (http://www.emertxe.com) 
*Date              : Fri 13 Agust  2021 16:00:04 IST
*File              : mqtt_esp32.ino
*Title             : This sketch demonstrates the capabilities of the pubsub library in combination
*                    with the ESP32 board/library.
*Description       : Basic ESP8266 MQTT example                     
*                    It connects to an MQTT server then:
*                    publishes "hello world" to the topic "outTopic" every two seconds
*                    subscribes to the topic "inTopic", printing out any messages
*                    it receives. NB - it assumes the received payloads are strings not binary
*                    If the first character of the topic "inTopic" is an 1, switch ON the ESP Led, else switch it off
*                    It will reconnect to the server if the connection is lost using a blocking
*                    reconnect function. See the 'mqtt_reconnect_nonblocking' example for how to achieve the same result 
*                    without blocking the main loop.
*Installation      : Libraries to be installed:
*                    Open the "Tools -> Library Manger -> search for pubsubclient
*                    select pusubclient by Nick 'O leary and install the latest version
*                    install mosquito broqer on the system
*Execution Steps   : Client : laptop, Serveer : ESP32, Broqer : Mosquito
*                    To subscribe to the topic from server, on client terminal typr
*                    "mosquitto_sub  -t out Topic -u "username" -P "password""
*----------------------------------------------------------------------------------------------------------------------------*/



#include 
#include 

// Update these with values suitable for your network.

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

const char* mqtt_server = "192.168.43.118";

WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[50];
int value = 0;

void setup_wifi() {

  delay(10);
  // We start by connecting to a WiFi network
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  randomSeed(micros());

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) { Serial.print((char)payload[i]); } Serial.println(); // Switch on the LED if an 1 was received as first character if ((char)payload[0] == '1') { digitalWrite(BUILTIN_LED, LOW); // Turn the LED on (Note that LOW is the voltage level // but actually the LED is on; this is because // it is active low on the ESP-01) } else { digitalWrite(BUILTIN_LED, HIGH); // Turn the LED off by making the voltage HIGH } } void reconnect() { // Loop until we're reconnected while (!client.connected()) { Serial.print("Attempting MQTT connection..."); // Create a random client ID String clientId = "ESP8266Client-"; clientId += String(random(0xffff), HEX); // Attempt to connect if (client.connect(clientId.c_str(), "jaya", "123qwe")) { Serial.println("connected"); // Once connected, publish an announcement... client.publish("outTopic", "hello world"); // ... and resubscribe client.subscribe("inTopic"); } else { Serial.print("failed, rc="); Serial.print(client.state()); Serial.println(" try again in 5 seconds"); // Wait 5 seconds before retrying delay(5000); } } } void setup() { pinMode(BUILTIN_LED, OUTPUT); // Initialize the BUILTIN_LED pin as an output Serial.begin(115200); setup_wifi(); client.setServer(mqtt_server, 1883); client.setCallback(callback); } void loop() { if (!client.connected()) { reconnect(); } client.loop(); long now = millis(); if (now - lastMsg > 2000) {
    lastMsg = now;
    ++value;
    snprintf (msg, 50, "hello world #%ld", value);
    Serial.print("Publish message: ");
    Serial.println(msg);
    client.publish("outTopic", msg);
  }
}