Assignment: Networking and Communication

My this week's assignment is divided into to three parts

1. Aurdino to Arduino using I2C
2. Xiao RP2040 to Arduino UNO using I2C
3. NodeMCU (ESP8266) to NodeMCU using wireless connection

I2C Between Arduinos

I referred to the Instructables link, I2C Between Arduinos by Cornelam. I2C (Inter-Integrated Circuit) is a serial communication protocol that lets multiple devices (like sensors or other Arduinos) talk using just two wires: SDA – Serial Data Line SCL – Serial Clock Line One Arduino acts as the Master, and others as Slaves. Each slave has a unique address, and the master controls all communication. Efficient for connecting many devices. Less wiring. Used for sensor modules, EEPROMs, other Arduinos, etc.

Wire connections
Connect pins A4/SDA and A5/SCL on one Arduino to the same pins on the other one.
The GND line has to be common for both Arduinos. Connect it with a jumper.
Further, I connected an LED at pin 12 and GND to slave Aurdino.

Note: Remember never to connect 5 V and 3.3 V Arduinos together. It won't hurt the 5V Arduino, but it will certainly annoy its 3.3 V!

Master Code

            #include 

            int slaveAddress = 9;  // Slave I2C address (same as in the slave code)
            
            void setup() {
              // Start the I2C communication as master
              Wire.begin(); 
              
              // Start the serial communication for debugging
              Serial.begin(9600);
              delay(1000);  // Wait for Serial to initialize
            }
            
            void loop() {
              // Send a command to the slave to blink the LED
              Wire.beginTransmission(slaveAddress);
              Wire.write('1');  // Send the command '1' to make the slave blink the LED
              Wire.endTransmission();
            
              // Print to Serial Monitor
              Serial.println("Sent command to blink LED");
            
              // Wait 2 seconds before sending the next command
              delay(2000);
            }
            

Slave Code

        #include 

        int LED = 12;  // Pin for the LED
        int x = 0;     // Variable to store received data
        
        void setup() {
          // Define the LED pin as Output
          pinMode(LED, OUTPUT);
        
          // Start the I2C Bus as Slave with address 9
          Wire.begin(9); 
          
          // Attach the receive function to handle I2C communication
          Wire.onReceive(receiveEvent);
        
          // Start serial communication for debugging
          Serial.begin(9600);
        }
        
        void receiveEvent(int bytes) {
          x = Wire.read();  // Read the byte sent from the master
        }
        
        void loop() {
          // Print the received value to Serial Monitor for debugging
          Serial.print("Received value: ");
          Serial.println(x);
        
          // If the value received is '1', blink the LED every 1 second
          if (x == '1') {
            digitalWrite(LED, HIGH);   // Turn the LED on
            delay(1000);                // Wait for 1 second
            digitalWrite(LED, LOW);    // Turn the LED off
            delay(1000);                // Wait for 1 second
          }
        
          // Optional: Small delay to avoid overloading the Serial Monitor
          delay(100);
          }

Here:
LED is the pin where the LED is connected and x stores the received data from the master.

Once the code was uploaded to both the Arduino's and the program ran smoothly, the code was stored in the memory for aurdino. So I removed the USB cables for both and gave a Power battery supply to the Master Arduino. The Arduino didnt work on a Lower Battery Supply. It needed a Supply of 5V or above.
Note: Use the VIN pin for to power the Arduino, as VIN + GNd goes through regulator and powers it smoothly.

Xiao RP2040 to Arduino UNO using I2C

Referring to Documentation of my senior, Siddharth Agarwal for Xiao RP2040 to Arduino UNO using I2C. I learnt a few things from the documentation Like:

One, RP2040 to RP2040 does not work due to a bug in the chip itself, and Two, When connecting RP2040 to anything else, to be cautious of the voltage difference.

He has added my professor Jesal Sir's Quote which I learnt the hard way buy burning a Xaio. Quoting “One has to be careful here, since the XIAO operates at 3.3 V while the Uno operates at 5 V. The I2C connection operates at whatever the Master is operating at. So the XIAO being the Primary or Master would work for the Uno but not the other way !"

Wire connections

SDA (D4) [XIAO] to SDA (A4) [Uno]

SCL (D5) [XIAO] to SCL (A5) [Uno]

common GND

LED on Arduino and pin 12 and GND

Master Code for Xaio

    #include 

        int slaveAddress = 9;  // The address of the Arduino Uno (slave)
        
        void setup() {
          // Start the I2C communication as master
          Wire.begin(); 
          
          // Start the serial communication for debugging
          Serial.begin(9600);
          delay(1000);  // Wait for Serial to initialize
        }
        
        void loop() {
          // Send a command to the slave to blink the LED
          Wire.beginTransmission(slaveAddress);
          Wire.write('1');  // Send the command '1' to make the slave blink the LED
          Wire.endTransmission();
        
          // Print to Serial Monitor
          Serial.println("Sent command to blink LED");
        
          // Wait 2 seconds before sending the next command
          delay(2000);
        }

Slave Code for Arduino

#include 

    int LED = 12;  // Pin for the LED
    int x = 0;     // Variable to store received data
    
    void setup() {
      // Define the LED pin as Output
      pinMode(LED, OUTPUT);
    
      // Start the I2C Bus as Slave with address 9
      Wire.begin(9); 
      
      // Attach the receive function to handle I2C communication
      Wire.onReceive(receiveEvent);
    
      // Start serial communication for debugging
      Serial.begin(9600);
    }
    
    void receiveEvent(int bytes) {
      x = Wire.read();  // Read the byte sent from the master
    }
    
    void loop() {
      // Print the received value to Serial Monitor for debugging
      Serial.print("Received value: ");
      Serial.println(x);
    
      // If the value received is '1', blink the LED every 1 second
      if (x == '1') {
        digitalWrite(LED, HIGH);   // Turn the LED on
        delay(1000);                // Wait for 1 second
        digitalWrite(LED, LOW);    // Turn the LED off
        delay(1000);                // Wait for 1 second
      }
    
      // Optional: Small delay to avoid overloading the Serial Monitor
      delay(100);
    }

Final Working

NodeMCU to NodeMCU

The NodeMCU uses an ESP8266 microcontroller which can communicate wirelessly over wi-fi or bluetooth. In this week, we communicate between the nodeMCUs using a wireless communication protocol called ESPNow, which runs on top of WiFi. Again I referred to Siddharth's Documentation for Node MCU connection

Difference between NODE MCU and ESP32

The NodeMCU and ESP32 are both popular microcontroller boards used in IoT and embedded projects, but they differ in capabilities, hardware, and use cases.

Node MCU pinout: Setting up the IDE

In order to program the NodeMCU, we need to first install the necessary drivers. This can be found on this link Silicone Labs for Arduino IDE. Most NodeMCU boards use a CP210x USB to UART bridge made by Silicon Labs. Without the correct driver, your computer might not detect the board properly, and you won't be able to upload code from the Arduino IDE or any other development environment.

I installed the Universal windows driver and ran the program on my computer, and run the programme on software.

Board setup on Arduino IDE

I opened up Arduino IDE and went to “Preferences” under File. There, under “Additional Boards Manager URL” I added the following link: https://arduino.esp8266.com/stable/package_esp8266com_index.json and finally, I went to the Board Manager under Tools and searched for ESP8266 by Community and installed it.

Generating Mac address

To start with any wireless communication, we need to first find the Mac Address of the microcontroller we are using. Mac Address has nothing to do with the MacBook or Apple and actually stands for “Media Access Control Address”. It is the unique address/identifier of a controller that can communicate wirelessly. You simply run the Mac Address code after connecting your microcontroller and once uploaded, hit the “Reset” button on your microcontroller and look at your Serial Monitor. You will find the unique 6-figure address of your controller.

Add Mac Address code.

                // For ESP 32:
                
                // #include 
                
                
                // For ESP8266
                #include 
                
                void setup(){
                   Serial.begin(115200);
                   delay(500);
                   Serial.println();
                   Serial.print("MAC: ");
                   Serial.println(WiFi.macAddress());
                }
                void loop(){}

Upload the below code to Master code. In the Mac address put the Secondary's MAC Address.

    #include    // initializing the required resource libraries
        #include        
        uint8_t broadcastAddress[] = {0x30,0x30,0xF9,0x17,0xF8,0x94};  // Secondary's MAC Address 2C:f4:32:OE:EO:F8
        
        
        #define BUTTON_PIN 13  // The ESP8266 pin D7 connected to button
        
        
        typedef struct struct_message {                     //create a structure called "message" and add the contents of the message
          int btnstate;                                    //integer value "c"            
        } struct_message;                                        
        
        
        struct_message myData;       
                               // Create a struct_message called myData
        unsigned long lastTime = 0; 
        unsigned long timerDelay = 1000;  // send readings timer
        
        void OnDataSent(uint8_t *mac_addr, uint8_t sendStatus) {
          Serial.print("Last Packet Send Status: ");
          if (sendStatus == 0){
            Serial.println("Delivery success");
          }
          else{
            Serial.println("Delivery fail");
          }
        }
        
        void setup() {
          Serial.begin(115200);   // Init Serial Monitor
          WiFi.mode(WIFI_STA);   // Set device as a Wi-Fi Station
        
          // Init ESP-NOW
          if (esp_now_init() != 0) {
            Serial.println("Error initializing ESP-NOW");
            return;
          }
        
          // Once ESPNow is successfully Init, we will register for Send CB to
          // get the status of Trasnmitted packet
          esp_now_set_self_role(ESP_NOW_ROLE_CONTROLLER);
          esp_now_register_send_cb(OnDataSent);
          
          // Register peer
          esp_now_add_peer(broadcastAddress, ESP_NOW_ROLE_SLAVE, 1, NULL, 0);
          // Initialize the Serial to communicate with the Serial Monitor.
        
          pinMode(BUTTON_PIN, INPUT_PULLUP); // Configure the ESP8266 pin as a pull-up input: HIGH when the button is open, LOW when pressed.
        }
        
        void loop() {
          if ((millis() - lastTime) > timerDelay) {
         
          //int button_state = digitalRead(BUTTON_PIN);  // read the state of the switch/button:
          myData.btnstate = digitalRead(BUTTON_PIN); 
          Serial.println(myData.btnstate); // print out the button's state
         esp_now_send(broadcastAddress, (uint8_t *) &myData, sizeof(myData));
         lastTime = millis();
          
        }
        }

Upload the below code to slave code.

    #include 
        #include 
        
        #define LEDpin D7  //Connect LED on pin 2
        
        // Structure example to receive data
        // Must match the sender structure
        typedef struct struct_message {  //create a structure called "message" and add the contents of the messag
          int btnstate;  //integer value "State"
        } struct_message;
        
        struct_message myData; // Create a struct_message called myData
        
        // Callback function that will be executed when data is received
        void OnDataRecv(uint8_t *mac, uint8_t *incomingData, uint8_t len) {
          memcpy(&myData, incomingData, sizeof(myData));
          Serial.print("Received state: ");
          Serial.println(myData.btnstate);
          Serial.println();
        }
        
        void setup() {
          pinMode(LEDpin, OUTPUT); //Define LED as output
          Serial.begin(115200);  // Initialize Serial Monitor
          WiFi.mode(WIFI_STA);   // Set device as a Wi-Fi Station
        
          // Init ESP-NOW
          if (esp_now_init() != 0) {
            Serial.println("Error initializing ESP-NOW");
            return;
          }
        
          // Once ESPNow is successfully Init, we will register for recv CB to
          // get recv packer info
          esp_now_set_self_role(ESP_NOW_ROLE_SLAVE);
          esp_now_register_recv_cb(OnDataRecv);
        }
        
        void loop() {
          if (myData.btnstate == 0) {
            digitalWrite(LEDpin, HIGH);
          } else {
            digitalWrite(LEDpin, LOW);
          }
        }

As you can see, I uploaded an LED blink code to the Master Node MCU to blink and LED at the Slave Node MCU and the Code Uploaded successfully.

#define ledPin 1  // D1 = GPIO5 on NodeMCU

    void setup() {
      pinMode(ledPin, OUTPUT);  // Set D1 as an OUTPUT pin
    }
    
    void loop() {
      digitalWrite(ledPin, HIGH);  // Turn the LED ON
      delay(1000);                 // Wait for 1 second
      digitalWrite(ledPin, LOW);   // Turn the LED OFF
      delay(1000);                 // Wait for 1 second
    }
    

Learning and Process

During the Networking and Communication week, I attempted to establish communication between two NodeMCU boards. I successfully uploaded the code onto both boards; however, there was no visible response from the NodeMCUs.

Initially, I suspected a networking issue, but I observed that even a single NodeMCU, when tested independently, showed no action. This led me to investigate further and conclude that the problem likely lies in the code configuration — specifically, how the pins were defined and managed.

Thus I tried different GPIO pin confuguration like

#define ledPin 5  // Correct GPIO for D1

However, with multiple attempts, the code didnt work. I am yet to debug the issue for the same. Considering the time constrains I moved forward with the Group assignment as the Node MCU was for my learning experiance and not related to my final project.