HC-05/HC-06 Bluetooth Module

				
					#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// OLED Screen parameters
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Display position tracking variable
int currentY = 10;         // The current Y-coordinate position (starting from the second row)
const int LINE_HEIGHT = 10; // Height of each row
const int MAX_Y = SCREEN_HEIGHT - LINE_HEIGHT; // Maximum Y coordinate
const int FIXED_LINE_Y = 0; // Fixed Y coordinate of the row

String bluetoothData = "";
bool newData = false;
bool isConnected = false;
unsigned long lastDataTime = 0;
const unsigned long DATA_TIMEOUT = 500; // Data reception timeout time (ms)

void setup() {
  // Initialize serial communication (connected to the Bluetooth module)
  Serial.begin(9600);
  
  // Initialize the OLED display screen
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Loop termination
  }
  
  // Initialize display settings
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  
  // Draw the fixed first row
  drawFixedLine();
  
  // Initial display information (starting from the second line)
  display.setCursor(0, currentY);
  display.println("Initializing...");
  currentY += LINE_HEIGHT;
  display.display();
  
  delay(1000);
  
  // Clear the content area but keep the fixed rows.
  clearContentArea();
  currentY = 10; // Reset the Y coordinate of the content area
  display.setCursor(0, currentY);
  display.println("Waiting for");
  currentY += LINE_HEIGHT;
  display.println("Bluetooth connection");
  currentY += LINE_HEIGHT;
  display.display();
  
  Serial.println("System ready");
  Serial.println("Connect your phone via Bluetooth");
}

void loop() {
  checkConnection();
  receiveBluetoothData();
  
  // Check if the time limit has been exceeded. If so, consider the data reception complete.
  if(isConnected && bluetoothData.length() > 0 && 
     millis() - lastDataTime > DATA_TIMEOUT) {
    newData = true;
  }
  
  if(newData) {
    updateDisplay();
    newData = false;
  }
  
  delay(10); // Short delay, reducing CPU usage
}

// Draw the fixed first row
void drawFixedLine() {
  display.setCursor(0, FIXED_LINE_Y);
  display.println("Received Data:"); // The fixed content of the first line
}

// Clear the content area (keep the first row)
void clearContentArea() {
  // Only clear the area below the first row.
  display.fillRect(0, LINE_HEIGHT, SCREEN_WIDTH, SCREEN_HEIGHT - LINE_HEIGHT, SSD1306_BLACK);
}

void checkConnection() {
  if(Serial.available() > 0 && !isConnected) {
    isConnected = true;
    clearContentArea(); // Only clear the content area
    currentY = 10; // Reset the Y coordinate of the content area
    display.setCursor(0, currentY);
    display.println("Connected!");
    currentY += LINE_HEIGHT;
    display.println("Send message now");
    currentY += LINE_HEIGHT;
    display.display();
    delay(1000);
  }
}

void receiveBluetoothData() {
  while(Serial.available() > 0) {
    char receivedChar = Serial.read();
    
    // Update the time of the last received data
    lastDataTime = millis();
    
    // Filter out the carriage return and line feed characters, but do not use them as the end markers.
    if(receivedChar != '\n' && receivedChar != '\r') {
      bluetoothData += receivedChar;
      newData = false; // New data has been received. Reset the flag for new data.
    } else if(bluetoothData.length() > 0) {
      // If a carriage return is received followed by data, it is considered that a message has ended.
      newData = true;
    }
    
    // Prevent memory issues caused by excessively long strings
    if(bluetoothData.length() > 100) {
      bluetoothData = bluetoothData.substring(bluetoothData.length() - 100);
    }
    
    delay(2);
  }
}

void updateDisplay() {
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  
  // Calculate the number of rows required for the current message
  int linesNeeded = 1;
  if(bluetoothData.length() > 16) {  // Each line can have a maximum of 16 characters.
    linesNeeded = (bluetoothData.length() + 15) / 16;  // round up to an integer
  }
  
  // Check if it will exceed the screen. If so, clear the content area (keep the first row).
  if(currentY + linesNeeded * LINE_HEIGHT > MAX_Y) {
    clearContentArea(); // Only clear the content area
    currentY = 10; // Reset to the top of the content area
  }
  
  // Display new messages and support automatic line wrapping (starting from the second line)
  for(int i = 0; i < bluetoothData.length(); i += 16) {
    String line = bluetoothData.substring(i, min(i + 16, bluetoothData.length()));
    display.setCursor(0, currentY);
    display.println(line);
    currentY += LINE_HEIGHT;
    
    // If you reach the bottom of the screen, clear the content area and start over from the beginning.
    if(currentY > MAX_Y) {
      clearContentArea(); // Only clear the content area
      currentY = 10; // Reset to the top of the content area
    }
  }
  
  // Redraw the fixed rows to ensure they are not covered.
  drawFixedLine();
  
  display.display();
  
  // Debugging output
  Serial.print("Displayed: ");
  Serial.println(bluetoothData);
  
  // Clear the data buffer and prepare to receive new data.
  bluetoothData = "";
}