// Transmitter code (Arduino UNO to Arduino UNO communication)
// this version includes the use of potentiometer to set the transmission bitrate (bps) in the setup funtion (to change the bitrate, reset the MCU )
// The bitrate is selected by adjusting the potentiometer and pressing the pushbutton to exit WHILE loop
// In the LOOP function the pushbutton is used to restart transmission (resend message)
// The receiver part can be updated with pushbutton, that resets receiver (ground the reset pin) to wait for new incoming message

#include <LiquidCrystal.h>

// Pin assignments
#define buttonPin 2
#define LCD_D4 4
#define LCD_D5 5
#define LCD_D6 6
#define LCD_D7 7
#define LCD_RS 8
#define LCD_EN 9
const int ledPin = 11;
const unsigned long bitDuration = 1000000;
unsigned long lastSendTime = 0;        
const unsigned long sendInterval = 1000;  // Interval between full messages
const byte preamble = 0xAA; // Preamble to signal start of new message

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  unsigned long currentTime = millis();
  if (currentTime - lastSendTime >= sendInterval) {
    sendPreamble();
    String message = "Hello, World!";
    Serial.println("\nSending message:");
    for (int i = 0; i < message.length(); i++) {
      byte data = message[i];
      uint16_t encoded = hammingEncode(data);
      Serial.print((char)data);
      sendHamming(encoded, true);
      delay(100); // Short delay between characters for clarity
    }
    Serial.println("\nMessage sent.");
    lastSendTime = currentTime;  // Update last send time
  }
}

void sendPreamble() {
  for (int i = 0; i < 8; i++) {
    sendBit((preamble >> i) & 1);
  }
  Serial.println("\nPreamble sent.");
}

uint16_t hammingEncode(byte data) {
  uint16_t encoded = 0;
  // Insert data bits into their positions (positions 3, 5, 6, 7, 9, 10, 11, 12)
  encoded |= (data & 0x01) << 2;
  encoded |= (data & 0x02) << 3;
  encoded |= (data & 0x04) << 3;
  encoded |= (data & 0x08) << 4;
  encoded |= (data & 0x10) << 4;
  encoded |= (data & 0x20) << 4;
  encoded |= (data & 0x40) << 4;
  encoded |= (data & 0x80) << 5;
  
  // Calculate parity bits and place them at positions 1, 2, 4, 8
  for (int i = 1; i <= 12; i *= 2) {
    int parity = 0;
    // Check all bits where the ith bit of the index is 1
    for (int j = 1; j <= 12; j++) {
      if ((j & i) && (encoded & (1 << j))) parity ^= 1;
    }
    encoded |= parity << i;
  }
  return encoded;
}

void sendHamming(uint16_t encoded, bool logBits) {
  Serial.print("\nBits: ");
  for (int i = 0; i < 12; i++) {
    bool bit = (encoded >> i) & 1;
    sendBit(bit);
    if (logBits) {
      Serial.print(bit ? "10" : "01");
    }
  }
  Serial.print("\n"); // Move to the next line after bits are displayed
}

void sendBit(bool bit) {
  unsigned long startTime = micros();
  if (bit) {
    digitalWrite(ledPin, LOW);
    while (micros() - startTime < bitDuration / 2);
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, HIGH);
    while (micros() - startTime < bitDuration / 2);
    digitalWrite(ledPin, LOW);
  }
  while (micros() - startTime < bitDuration);
}