Wireless Laser Data Transmission (LiFi) – 100 b/s Performance Overview

Necessary tools and machines

	Soldering iron (generic)
	Solder Wire, Lead Free

Apps and online services

Arduino IDE

About this project

This project is made of two parts the emitter and the receiver it can be used to send texts over laser using a keyPad and an LCD

Code

• LI-FI Transmitter Code V 2.0
• LI-FI Receiver Code V 2.0

LI-FI Transmitter Code V 2.0C/C++

/*LI-FI Transmitter Code V 2.0
   Written By HOUALEF AHMED RAMZI
   Started on 29-9-2020
   Last Update on  14-10-2020
*/
#define LaserPin 2
#include <LiquidCrystal.h>
const int rs = 12, en = 11, d4 = 6, d5 = 5, d6 = 4, d7 = 3;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
int incomingchar;
int KeyPad_R[] = {A2, A1, 9, 7}; //The KeyPad rows
int KeyPad_C[] = {8, 10, A3}; // The KeyPad Columns
int KeyReturn = 0; // The Output of the Keypad Function from 1-12
int ABC; //variable used to code 3 chars using one button
int Row; //variable used in the Keypad function
int Column;//variable used in the Keypad function
int StCursor = 0; //variable for the Cursor Control
int NdCursor = 0; //variable for the Cursor Control
int outcomingmatrix[32][5]; //The DATA Buffer
int m = 0;// variable used to know the length of the outcomingmatrix to avoid sending all the 32*5 emty buffer
int A[] = {1, 1, 1, 1, 0}, B[] = {0, 0, 0, 1, 0}, C[] = {0, 0, 0, 1, 1}, D[] = {0, 0, 1, 0, 0}, E[] = {0, 0, 1, 0, 1}, F[] = {0, 0, 1, 1, 0}, G[] = {0, 0, 1, 1, 1}, H[] = {0, 1, 0, 0, 0};
int I[] = {0, 1, 0, 0, 1}, J[] = {0, 1, 0, 1, 0}, K[] = {0, 1, 0, 1, 1}, L[] = {0, 1, 1, 0, 0}, M[] = {0, 1, 1, 0, 1}, N[] = {0, 1, 1, 1, 0}, O[] = {0, 1, 1, 1, 1}, P[] = {1, 0, 0, 0, 0};
int Q[] = {1, 0, 0, 0, 1}, R[] = {1, 0, 0, 1, 0}, S[] = {1, 0, 0, 1, 1}, T[] = {1, 0, 1, 0, 0}, U[] = {1, 0, 1, 0, 1}, V[] = {1, 0, 1, 1, 0}, W[] = {1, 0, 1, 1, 1}, X[] = {1, 1, 0, 0, 0};
int Y[] = {1, 1, 0, 0, 1}, Z[] = {1, 1, 0, 1, 0}, SPACE[] = {1, 1, 1, 1, 1}; // a small data base to stor all coded charachters

void setup() {
  lcd.begin(16, 2);
  pinMode(LaserPin, OUTPUT);
  Serial.begin(9600);
  for (int i; i < 4; i++) {
    pinMode( KeyPad_R[i], OUTPUT);
  }
  for (int j; j < 3; j++) {
    pinMode( KeyPad_C[j], INPUT);
  }
  lcd.print("HOUALEF RAMZI");
  delay(5000);
  lcd.clear();
  lcd.setCursor(0,0);

}
void conv(int alpha [5], char Char ) { // TO FILL THE OUTPUT BUFFER FROM THE DATA BASE
  for (int i = 0; i < 5; i++) {
    outcomingmatrix[m][i] = alpha[i];
  }
  lcd.print(Char);
}

void start_bit() { //THE START BIT
  digitalWrite(LaserPin, HIGH);
  delay(9);
  digitalWrite(LaserPin, LOW);
}

void KeyPad() { // OUTPUTS THE BUTTON'S NUMBER PRESSED FROM 1 TO 12
  for (int i = 0; i < 4; i++) {
    digitalWrite( KeyPad_R[i], HIGH);
    for (int j = 0; j < 3; j++) {
      if (digitalRead(KeyPad_C[j]) == 1) {
        Row = i;
        Column = j;
        digitalWrite( KeyPad_R[i], LOW);

        if (Row == 0) {
          switch (Column) {
            case 0: KeyReturn = 1; break; case 1: KeyReturn = 2; break; case 2: KeyReturn = 3; break;
          }
        }
        if (Row == 1) {
          switch (Column) {
            case 0: KeyReturn = 4; break; case 1: KeyReturn = 5; break; case 2: KeyReturn = 6; break;
          }
        }
        if (Row == 2) {
          switch (Column) {
            case 0: KeyReturn = 7; break; case 1: KeyReturn = 8; break; case 2: KeyReturn = 9; break;
          }
        }
        if (Row == 3) {
          switch (Column) {
            case 0: KeyReturn = 10; break; case 1: KeyReturn = 11; break; case 2: KeyReturn = 12; break;
          }
        }
      }
    }
  } Serial.println(KeyReturn);
}

void KeyToAscii(int KeyN, int FirtAsciiValue) { // TO CONVERT DATA FROM THE KEYPAD TO THE ASCII VALUE TO WORK WITH THE CONV FUNCTION ABOVE THAT'S HOW WE CAN USE BOTH OF SERIAL MONITOR AND THE KEYPAD
  if (KeyReturn == KeyN) {
    incomingchar = FirtAsciiValue + ABC;
    ABC++;
    if (ABC == 3) {
      ABC = 0;
    }
  }

}

void CursorControler() {
  lcd.setCursor(StCursor, NdCursor);
  if (KeyReturn == 10) { //TO CONFIRM THE CHARACTERS BECAUSE 11 IN THE CONFIRM BUTTON
    delay(100);
    StCursor++;
    m++;
  }

  if (StCursor == 16) { // TO WRITE IN NEW LINE WHEN THE FIRST IS FULL
    StCursor = 0;
    NdCursor = 1;
  }
}

void loop() {
  KeyPad();
  delay(150);
  CursorControler();
  KeyToAscii(1, 65); KeyToAscii(2, 68); KeyToAscii(3, 71); KeyToAscii(4, 74); KeyToAscii(5, 77); KeyToAscii(6, 80); KeyToAscii(7, 83); KeyToAscii(8, 86); KeyToAscii(9, 89); KeyToAscii(11, 32);

  switch (incomingchar) {
    case 65: conv(A, 'A'); break; case 66: conv(B, 'B'); break; case 67: conv(C, 'C'); break; case 68: conv(D, 'D'); break; case 69: conv(E, 'E'); break; case 70: conv(F, 'F'); break; case 71: conv(G, 'G'); break;
    case 72: conv(H, 'H'); break; case 73: conv(I, 'I'); break; case 74: conv(J, 'J'); break; case 75: conv(K, 'K'); break; case 76: conv(L, 'L'); break; case 77: conv(M, 'M'); break; case 78: conv(N, 'N'); break;
    case 79: conv(O, 'O'); break; case 80: conv(P, 'P'); break; case 81: conv(Q, 'Q'); break; case 82: conv(R, 'R'); break; case 83: conv(S, 'S'); break; case 84: conv(T, 'T'); break; case 85: conv(U, 'U'); break;
    case 86: conv(V, 'V'); break; case 87: conv(W, 'W'); break; case 88: conv(X, 'X'); break; case 89: conv(Y, 'Y'); break; case 90: conv(Z, 'Z'); break; case 32: conv(SPACE, ' '); break; case 33: conv(SPACE, ' '); break;
  }
  //TO USE THE SPACE FROM THE SERIAL MONITOR YOU HAVE TO CHANGE CASE 91 TO CASE 32
  if (KeyReturn == 12) { //TO SEND DATA BECAUSE 12 IS THE SEND BUTTON
    delay(100);
    for (int j = 0; j < m; j++) {
      start_bit();
      for (int i = 0; i < 5; i++) {
        digitalWrite(LaserPin, outcomingmatrix[j][i]);
        delay(10);
      }
      digitalWrite(LaserPin, LOW);
      delay(20);
    }
    for (int k = 0; k < 32; k++) {
      for (int l = 0; l < 5; l++) {
        outcomingmatrix[k][l] = 0; // To Clear The buffer
      }
    }
  }
  incomingchar = 0; // To Avoid continuous DATA storing
  KeyReturn = 0; // That means no button is pressed currently
}

LI-FI Receiver Code V 2.0C/C++

/*LI-FI Receiver Code V 2.0
   Written By HOUALEF AHMED RAMZI
   Started on 29-9-2020
   Last Update on  14-10-2020
*/
#include <LiquidCrystal.h>
#define SolarCell A0 //To define the input pin of the solarcell
int StCursor = 0; // To control the lcd Cursor
int A[] = {1, 1, 1, 1, 0}, B[] = {0, 0, 0, 1, 0}, C[] = {0, 0, 0, 1, 1}, D[] = {0, 0, 1, 0, 0}, E[] = {0, 0, 1, 0, 1}, F[] = {0, 0, 1, 1, 0}, G[] = {0, 0, 1, 1, 1}, H[] = {0, 1, 0, 0, 0};
int I[] = {0, 1, 0, 0, 1}, J[] = {0, 1, 0, 1, 0}, K[] = {0, 1, 0, 1, 1}, L[] = {0, 1, 1, 0, 0}, M[] = {0, 1, 1, 0, 1}, N[] = {0, 1, 1, 1, 0}, O[] = {0, 1, 1, 1, 1}, P[] = {1, 0, 0, 0, 0};
int Q[] = {1, 0, 0, 0, 1}, R[] = {1, 0, 0, 1, 0}, S[] = {1, 0, 0, 1, 1}, T[] = {1, 0, 1, 0, 0}, U[] = {1, 0, 1, 0, 1}, V[] = {1, 0, 1, 1, 0}, W[] = {1, 0, 1, 1, 1}, X[] = {1, 1, 0, 0, 0};
int Y[] = {1, 1, 0, 0, 1}, Z[] = {1, 1, 0, 1, 0}, SPACE[] = {1, 1, 1, 1, 1};

const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
int Cell_Input; // The input of the Solar-Cell
int Threshold;
int info[5]; //The received DATA

LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
void setup() {
  pinMode(A0, INPUT);
  Serial.begin(9600);
  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  Threshold = analogRead(SolarCell) + 10;
  lcd.print("READY TO RECEIVE");
  delay(5000);
  lcd.clear();

}

void BufferClear() { // The clear the buffer
  for (int i = 0; i < 5; i++) {
    info[i] = 0;
  }
}

void check_condition(int received_bits[5], int Binaryalpha[5], char Lcdalpha) {//To compare the received bits With the data base
  if (received_bits[0] == Binaryalpha[0] && received_bits[1] == Binaryalpha[1] && received_bits[2] == Binaryalpha[2] && received_bits[3] == Binaryalpha[3] && received_bits[4] == Binaryalpha[4]) {
    lcd.print(Lcdalpha);
    CursorControler();
  }
}

void CursorControler() { // To control the cursor
  StCursor++;
  if (StCursor == 16)
    lcd.setCursor(0, 1);
}

void loop() {
  Cell_Input = analogRead(SolarCell);
  if (Cell_Input > Threshold) { // the start bit detection
    delay(10); // timing
    for (int i = 0; i < 5; i++) { // save data
      if (analogRead(SolarCell) > Threshold) {
        info[i] = 1;
      }
      else {
        info[i] = 0;
      }
      delay(10);
    }

    check_condition(info, A, 'A'); check_condition(info, B, 'B'); check_condition(info, C, 'C'); check_condition(info, D, 'D');
    check_condition(info, E, 'E'); check_condition(info, F, 'F'); check_condition(info, G, 'G'); check_condition(info, H, 'H');
    check_condition(info, I, 'I'); check_condition(info, J, 'J'); check_condition(info, K, 'K'); check_condition(info, L, 'L');
    check_condition(info, M, 'M'); check_condition(info, N, 'N'); check_condition(info, O, 'O'); check_condition(info, P, 'P');
    check_condition(info, Q, 'Q'); check_condition(info, R, 'R'); check_condition(info, S, 'S'); check_condition(info, T, 'T');
    check_condition(info, U, 'U'); check_condition(info, V, 'V'); check_condition(info, W, 'W'); check_condition(info, X, 'X');
    check_condition(info, Y, 'Y'); check_condition(info, Z, 'Z'); check_condition(info, SPACE, ' ');
    BufferClear();
  }
}

Schematics