// https://forum.arduino.cc/t/arduino-uno-unable-to-work-with-external-power-supple/1465166/

bool debug = true; // for debug print statements

int trig[] = {12, 10, 8};
int echo[] = {13, 11, 9};
int duration[3];
int distance[3];
bool obstacle[3]; // bit packed array
int unsafeDistance = 5;
int obsTotal;
int stp = 0; // moved from setup() to global variables

int L298Npin[] = {2, 3, 4, 5, 6, 7}; // array to set pins as a batch

int enA = 3; // left motor // was 2 (a DIO pin) but needs a PWM pin (3)
int in1 = 2; // was 3 but only needs a DIO pin
int in2 = 4;

int enB = 5; // right motor // PWM pin
int in3 = 6;
int in4 = 7;

void setup() {
  if (debug) Serial.begin(115200); // need this for Serial printing
  for (byte i = 0; i < 3; i++) {
    pinMode(trig[i], OUTPUT);
    pinMode(echo[i], INPUT);
    pinMode(L298Npin[i], OUTPUT); // in1, ena, in2
    pinMode(L298Npin[i * 2], OUTPUT); // enB, in3, in4
    digitalWrite(L298Npin[i], LOW); // left motor (A) pins off
    digitalWrite(L298Npin[i * 2], LOW); // right motor (B) pins off
  }
  analogWrite(enA, 230); // moved these two, single-call lines from loop() to setup()
  analogWrite(enB, 250); // mismatched motors?
}

void loop() {
  while (stp == 0) {
    for (byte i = 0; i < 3; i++) { // three HC-SR04
      digitalWrite(trig[i], LOW);
      delayMicroseconds(2);
      digitalWrite(trig[i], HIGH);
      delayMicroseconds(10);
      digitalWrite(trig[i], LOW);
      duration[i] = pulseIn(echo[i], HIGH); // "time" changed to "duration" to avoid keyword conflict
      distance[i] = duration[i] * (0.034 / 2);    //speed of sound  = 0.034 cm/microsecond

      if (debug) debugoutput(distance[i], DEC, " Distance");

      if (distance[i] <= unsafeDistance)
        obstacle[i] = 1; // obstacle detected
      else
        obstacle[i] = 0; // obstacle not detected
    }

    obsTotal = obstacle[0] * 4 + obstacle[1] * 2 + obstacle[2];

    if (debug) debugoutput(obsTotal, BIN, "| obsTotal (BIN)");

    switch (obsTotal) {
      case B000: // stop
        drive (LOW, LOW, LOW, LOW);
        Serial.print(" end of line: stop");
        stp = 6;
        break;

      case B001: // left
        drive(LOW, LOW, HIGH, LOW);
        continue; // lets switch() test all case:s

      case B010:  // left for 0.5 sec
        drive(LOW, LOW, HIGH, LOW);
        delay(500);
        continue;

      case B011: // left
        drive(LOW, LOW, HIGH, LOW);
        continue;

      case B100: // right
        drive(HIGH, LOW, LOW, HIGH);
        continue;

      case B101:  // forward
        drive(HIGH, LOW, HIGH, LOW);
        continue;

      case B110: // right (again?)
        drive(HIGH, LOW, LOW, HIGH);
        continue;

      case B111:  //left for 0.5 sec
        drive (LOW, LOW, HIGH, LOW);
        delay(500);
        continue;

      default:  // error
        drive(LOW, LOW, LOW, LOW);
        stp = 5;
        break;
    }
    if (debug) Serial.println();
  }
}

void drive(bool i1, bool i2, bool i3, bool i4) { // four motor input signals
  digitalWrite(in1, i1);
  digitalWrite(in2, i2);
  digitalWrite(in3, i3);
  digitalWrite(in4, i4);
}

void debugoutput(int value, byte base, char text[]) {
  Serial.print(text);
  Serial.print(":");

  if (base == DEC) { // " " placeholders
    if (value < 100)
      Serial.print(" ");
    if (value < 10)
      Serial.print(" ");
  }
  if (base == BIN) { // "0" placeholders
    if  (value < 4)
      Serial.print("0");
    if (value < 2)
      Serial.print("0");
  }
  Serial.print(value, base);
  Serial.print(" ");
  if (base == BIN)
    Serial.println(); // end of line CRLF
}