Include Arduino H Include Softwareserial H // Hc

#include <Arduino.h>
#include <SoftwareSerial.h>

// HC-05: TX -> D10 (BT_RX), RX -> D11 (BT_TX)
// NOTE: Voltage divider (1kΩ + 2kΩ) required on D11 -> HC-05 RX to drop 5V -> 3.3V

#define BT_RX 10
#define BT_TX 11

// L298N direction pins
#define IN1 2
#define IN2 4
#define IN3 7
#define IN4 8

// L298N PWM speed pins
#define ENA 3
#define ENB 5

#define SPEED_DEFAULT 180  // 0–255, fallback speed if no slider value received
#define TURN_RATIO   0.45 // inner wheel fraction of currentSpeed (0.0=full pivot, 1.0=straight)


// Forward declarations
void stopMotors();
void moveForward(int spd);
void moveBackward(int spd);
void turnLeft(int spd);
void turnRight(int spd);

SoftwareSerial btSerial(BT_RX, BT_TX);

// ── Motor helpers ─────────────────────────────────────────────────────────────

void stopMotors() {
  digitalWrite(IN1, LOW); digitalWrite(IN2, LOW);
  digitalWrite(IN3, LOW); digitalWrite(IN4, LOW);
  analogWrite(ENA, 0);    analogWrite(ENB, 0);
}

// ── Motor truth table ────────────────────────────────────────────────────────
// Motor A (Left)  : IN1=HIGH, IN2=LOW  → forward  |  IN1=LOW,  IN2=HIGH → backward
// Motor B (Right) : IN3=LOW,  IN4=HIGH → forward  |  IN3=HIGH, IN4=LOW  → backward
//                  (B wires physically reversed, so logic is inverted)

void moveForward(int spd) {
  analogWrite(ENA, spd); analogWrite(ENB, spd);
  digitalWrite(IN1, LOW);  digitalWrite(IN2, HIGH);  // Motor A forward
  digitalWrite(IN3, HIGH); digitalWrite(IN4, LOW);   // Motor B forward
}

void moveBackward(int spd) {
  analogWrite(ENA, spd); analogWrite(ENB, spd);
  digitalWrite(IN1, HIGH); digitalWrite(IN2, LOW);   // Motor A backward
  digitalWrite(IN3, LOW);  digitalWrite(IN4, HIGH);  // Motor B backward
}

void turnLeft(int spd) {
  // Motor A backward (inner, slow), Motor B forward (outer, full) → pivot left
  int inner = (int)(spd * TURN_RATIO);
  analogWrite(ENA, inner); analogWrite(ENB, spd);
  digitalWrite(IN1, HIGH); digitalWrite(IN2, LOW);   // Motor A backward
  digitalWrite(IN3, HIGH); digitalWrite(IN4, LOW);   // Motor B forward
}

void turnRight(int spd) {
  // Motor A forward (outer, full), Motor B backward (inner, slow) → pivot right
  int inner = (int)(spd * TURN_RATIO);
  analogWrite(ENA, spd); analogWrite(ENB, inner);
  digitalWrite(IN1, LOW);  digitalWrite(IN2, HIGH);  // Motor A forward
  digitalWrite(IN3, LOW);  digitalWrite(IN4, HIGH);  // Motor B backward
}

// ── Global speed (updated by slider) ────────────────────────────────────────
int currentSpeed = SPEED_DEFAULT;  // live speed, set by slider command 'V0'–'V255'

// ── Setup ─────────────────────────────────────────────────────────────────────

void setup() {
  Serial.begin(9600);
  btSerial.begin(9600);

  pinMode(IN1, OUTPUT); pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT); pinMode(IN4, OUTPUT);
  pinMode(ENA, OUTPUT); pinMode(ENB, OUTPUT);

  stopMotors();

  Serial.println("Bluetooth Rover Ready!");
  Serial.println("Commands: F=Forward  B=Backward  L=Left  R=Right  S=Stop");
  Serial.println("          V0–V255=Speed slider");
}

// ── Loop ──────────────────────────────────────────────────────────────────────
// Strategy: read one byte at a time (never block).
// Direction commands are a single char (F/B/L/R/S).
// Slider commands start with 'V' followed by digits and end with '\n' or '\r'.

static String sliderBuf = "";   // accumulates digits after 'V'
static bool   inSlider  = false;

void loop() {
  while (btSerial.available()) {
    char c = (char)btSerial.read();

    // ── Slider mode: we already saw 'V', now collect digits ──────────────────
    if (inSlider) {
      if (c >= '0' && c <= '9') {
        sliderBuf += c;          // accumulate digit
      } else {
        // terminator (newline, carriage return, or next command char)
        if (sliderBuf.length() > 0) {
          currentSpeed = constrain(sliderBuf.toInt(), 0, 255);
          Serial.print(">> Speed set to "); Serial.println(currentSpeed);
        }
        sliderBuf = "";
        inSlider  = false;
        // fall through to handle 'c' as a command if it is one
        if (c == '\n' || c == '\r') continue;
      }
      if (inSlider) continue;   // still collecting digits
    }

    // ── Normal single-char command ───────────────────────────────────────────
    char cmd = toupper(c);
    switch (cmd) {
      case 'F': moveForward(currentSpeed);  Serial.println(">> Forward");  break;
      case 'B': moveBackward(currentSpeed); Serial.println(">> Backward"); break;
      case 'L': turnLeft(currentSpeed);     Serial.println(">> Left");     break;
      case 'R': turnRight(currentSpeed);    Serial.println(">> Right");    break;
      case 'S': stopMotors();               Serial.println(">> Stop");     break;
      case 'V': inSlider = true; sliderBuf = ""; break;  // start slider read
      default:  break;          // ignore newlines / unknown bytes
    }
  }
}