ROVIE: ESP32 Obstacle Avoiding Rover

#include <Arduino.h>
// 4WD line-following + obstacle-avoiding robot
// ESP32 DevKit v1 + L298N + 4x TT motors + 2x TCRT5000 IR + HC-SR04
//
// Left side (front-left + rear-left) share L298N bridge A (OUT1/OUT2, IN1/IN2, ENA).
// Right side (front-right + rear-right) share bridge B (OUT3/OUT4, IN3/IN4, ENB).

// --- Motor driver pins ---

// Forward declarations
void leftSpeed(int s);
void rightSpeed(int s);
void leftForward();
void leftReverse();
void rightForward();
void rightReverse();
void driveForward();
void turnLeft();
void turnRight();
void stopMotors();
long readDistanceCm();

const int IN1 = 13;  // Bridge A dir
const int IN2 = 14;  // Bridge A dir
const int IN3 = 26;  // Bridge B dir
const int IN4 = 27;  // Bridge B dir
const int ENA = 25;  // Bridge A speed (PWM) - LEFT
const int ENB = 33;  // Bridge B speed (PWM) - RIGHT

// --- Sensors ---
const int IR_LEFT  = 32; // TCRT5000 DO: LOW over black line
const int IR_RIGHT = 4;
const int TRIG = 16;
const int ECHO = 17;     // input-capable GPIO

// --- LEDC PWM setup (ESP32) ---
const int CH_A = 0;
const int CH_B = 1;
const int PWM_FREQ = 1000;
const int PWM_RES  = 8;   // 0..255

const int SPEED_FWD  = 200;
const int SPEED_TURN = 180;

const int OBSTACLE_CM = 20; // stop/avoid closer than this

void leftSpeed(int s)  { ledcWrite(CH_A, s); }
void rightSpeed(int s) { ledcWrite(CH_B, s); }

void leftForward()  { digitalWrite(IN1, HIGH); digitalWrite(IN2, LOW); }
void leftReverse()  { digitalWrite(IN1, LOW);  digitalWrite(IN2, HIGH); }
void rightForward() { digitalWrite(IN3, HIGH); digitalWrite(IN4, LOW); }
void rightReverse() { digitalWrite(IN3, LOW);  digitalWrite(IN4, HIGH); }

void driveForward() { leftForward(); rightForward(); leftSpeed(SPEED_FWD); rightSpeed(SPEED_FWD); }
void turnLeft()     { leftReverse(); rightForward(); leftSpeed(SPEED_TURN); rightSpeed(SPEED_TURN); }
void turnRight()    { leftForward(); rightReverse(); leftSpeed(SPEED_TURN); rightSpeed(SPEED_TURN); }
void stopMotors()   { leftSpeed(0); rightSpeed(0); }

long readDistanceCm() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);
  // 25ms timeout ~ 4.3m max
  unsigned long dur = pulseIn(ECHO, HIGH, 25000UL);
  if (dur == 0) return 999; // no echo = treat as clear
  return (long)(dur / 58);
}

void setup() {
  Serial.begin(115200);
  pinMode(IN1, OUTPUT); pinMode(IN2, OUTPUT);
  pinMode(IN3, OUTPUT); pinMode(IN4, OUTPUT);
  pinMode(IR_LEFT, INPUT); pinMode(IR_RIGHT, INPUT);
  pinMode(TRIG, OUTPUT); pinMode(ECHO, INPUT);

  ledcSetup(CH_A, PWM_FREQ, PWM_RES);
  ledcSetup(CH_B, PWM_FREQ, PWM_RES);
  ledcAttachPin(ENA, CH_A);
  ledcAttachPin(ENB, CH_B);

  stopMotors();
}

void loop() {
  long dist = readDistanceCm();

  // Obstacle avoidance takes priority
  if (dist <= OBSTACLE_CM) {
    stopMotors();
    delay(120);
    // back up briefly then pivot to look for a clear path
    leftReverse(); rightReverse();
    leftSpeed(SPEED_TURN); rightSpeed(SPEED_TURN);
    delay(300);
    turnRight();
    delay(400);
    stopMotors();
    return;
  }

  // Line following: DO LOW = over black line
  bool leftOnLine  = (digitalRead(IR_LEFT)  == LOW);
  bool rightOnLine = (digitalRead(IR_RIGHT) == LOW);

  if (!leftOnLine && !rightOnLine) {
    driveForward();               // both on white -> go straight
  } else if (leftOnLine && !rightOnLine) {
    turnLeft();                   // line drifted left -> steer left
  } else if (!leftOnLine && rightOnLine) {
    turnRight();                  // line drifted right -> steer right
  } else {
    // both on black (junction/stop mark) -> creep forward slowly
    driveForward();
    leftSpeed(SPEED_TURN); rightSpeed(SPEED_TURN);
  }
}