Networking and Communications

Individual assignment:


Design, build, and connect wired or wireless node(s)
with network or bus addresses and local input &/or
output device(s)


For this week's project, The master board will feature a switch to select the slave board. An LED on the slave board will indicate the chosen slave board. The slave board selection can be done using a push button on the master board.

I've decided to utilize the I2C protocol to facilitate this function.

I2C Communication Protocol


I2C, which stands for Inter-Integrated Circuit, is a bus interface connection protocol that is integrated into devices for serial communication.

It's a commonly used protocol for short-distance communication and is also referred to as Two Wire Interface (TWI).

The I2C communication protocol operates using only 2 bi-directional open-drain lines for data transmission, known as SDA and SCL. Both of these lines are initially pulled high.

I2C operates in 2 modes –

Every data bit transferred on the SDA line is synchronized by a transition from the high to low pulse of each clock signal on the SCL line.



As per the I2C protocols, the data line cannot change while the clock line is high;

It can only change when the clock line is low.

Since the devices on the I2C bus are actively low, pull-up resistors are required to keep lines high.

Data is transmitted in the form of packets consisting of 9 bits. The sequence of these bits includes:


Start and stop conditions

I2C protocols are generated by keeping the SCL line high and changing the level of SDA.

To generate a start condition, the SDA line is transitioned from high to low while keeping SCL high.

Conversely, to generate a stop condition, the SDA line transitions from low to high while keeping the SCL high.

A high Read/Write bit indicates that the master is sending the data to the slave, whereas a low Read/Write bit indicates that the master is receiving data from the slave.


Designing the Board

For the Master board , I'll be using the board developed during the electronics design week . This board features a push button. Additionally, it has the necessary I2C pins required for communication.


For the Slave board , I'll be designing a new board. I'll use the ATtiny412 microcontroller, which includes an LED and the necessary pinouts for I2C communication. Additionally, I'll ensure it supports burning the bootloader.


Here is the schematic diagram of the board


Here is the PCB layout



After obtaining the design file, I proceeded with the milling process.




After milling the board, I soldered the components in place. Here is the output.


Then, I replicated the same board design for the next slave.

To test the functionality of the slave boards, I uploaded the basic Blink example sketch from Arduino. Both boards are working fine.

Unfortunately, I forgot to record a video of the testing phase.

Next , I connected the master board with the slaves and began working on the software side of the project.


Code for master board

here is the prompt that i have given to generate this code using Chat GPT

Write an Arduino sketch that: 

#include <Wire.h>

const int buttonPin = 9; 
int counter = 0;        

void setup() {
  pinMode(buttonPin, INPUT_PULLUP); 
  Wire.begin();                     
}

void loop() {
  int buttonState = digitalRead(buttonPin);
  

  if (buttonState == LOW) {
    counter++; 
    
    
    int slaveAddress = (counter % 2 == 0) ? 8 : 9;
    int ledState = (counter % 2 == 0) ? 0 : 1;
    
    // Send command to toggle LED on the selected slave device
    Wire.beginTransmission(slaveAddress);
    Wire.write(ledState);
    Wire.endTransmission();  
    
    delay(500);
  }

  delay(100);
}

Explanation of the above code

Include the Wire Library 

#include <Wire.h>

Define Constants and Variables 

const int buttonPin = 9; // Pin connected to the push button
int counter = 0;         // Counter to alternate between slave devices

Setup Function 

void setup() 
{
  pinMode(buttonPin, INPUT_PULLUP); // Set the button pin as an input with internal pull-up resistor
  Wire.begin();                     // Join I2C bus
}

Loop Function 

void loop() {
  int buttonState = digitalRead(buttonPin); // Read the state of the button
  // If the button is pressed, toggle the LEDs on the slave devices
  if (buttonState == LOW) {
    counter++; // Increment counter
    // Determine which slave device to toggle based on the counter value
    int slaveAddress = (counter % 2 == 0) ? 8 : 9;
    int ledState = (counter % 2 == 0) ? 0 : 1;
    // Send command to toggle LED on the selected slave device
    Wire.beginTransmission(slaveAddress); // Start communication with the selected slave device
    Wire.write(ledState); // Send command to toggle LED based on the current LED state
    Wire.endTransmission();    // End communication
    delay(500); // Delay to debounce the button
  }

  delay(100); // Small delay between readings for stability
}



Code for slave board

here is the prompt that i have given to generate this code using Chat GPT 

#include <Wire.h>

const int ledPin = 13; 
int ledState = LOW;   

void setup() {
  pinMode(ledPin, OUTPUT); 
  digitalWrite(ledPin, ledState);
  
  Wire.begin(8); 
  // Wire.begin(9); // Uncomment this and comment the above line for the second slave with address #9
  Wire.onReceive(receiveEvent); 
}

void loop() {
  
  delay(100); // Small delay for stability
}

// Function to handle incoming data from the master
void receiveEvent(int howMany) {
  while (Wire.available()) {
    int command = Wire.read(); 
    if (command == 0) {
      ledState = LOW; 
    } else if (command == 1) {
      ledState = HIGH;
    }
    digitalWrite(ledPin, ledState);
  }
}

Explanation of the above code

Include the Wire Library 

#include <Wire.h>

Define Constants and Variables 

const int ledPin = 13; // Pin connected to the LED
int ledState = LOW;    // Variable to hold the current LED state

Setup Function 

void setup() {
  pinMode(ledPin, OUTPUT); // Set the LED pin as an output
  digitalWrite(ledPin, ledState); // Initialize the LED to the initial state
  Wire.begin(8); // Join I2C bus with address #8 for the first slave
  // Wire.begin(9); // Uncomment this and comment the above line for the second slave with address #9
  Wire.onReceive(receiveEvent); // Register the receive even

Loop Function 

void loop() {
  // Main loop does nothing, all the work is done in the receiveEvent function
  delay(100); // Small delay for stability

Receive Event Function 

// Function to handle incoming data from the master
void receiveEvent(int howMany) {
  while (Wire.available()) {
    int command = Wire.read(); // Read the command from the master
    if (command == 0) {
      ledState = LOW; // Turn off the LED
    } else if (command == 1) {
      ledState = HIGH; // Turn on the LED
    }
    digitalWrite(ledPin, ledState); // Update the LED state
  }
}


Here is the output I achieved.





Group assignment: click here


Send a message between two projects

Download Files

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