Variable won't increment in "if" statement

This project involves using ultrasonic sensors to detect walls so that a robot can navigate a course. The basic function of this code is to have my robot race around a track for three laps and then stop at the end of the third lap. The way I decided to count how may laps would be to count how many walls it sees in front of it. If it sees a wall with it's front sensor, it will turn 90 degrees left and keep going. Eventually, assuming everything goes well, it should be finished with the three laps after seeing a wall in front 12 times.

Anyway, my question involves counting how many walls that it sees. See my code below to see what I thought would work.

#include <Ultrasonic.h>
#include <Servo.h>
#include <ESP8266WiFi.h>
#include <math.h>

#define motorRpin D0
#define motorLpin D2

Servo motorR;
Servo motorL;

Ultrasonic usFront  (D8, D5);
Ultrasonic usRight  (D9, D6);
Ultrasonic usLeft   (D10, D7);

int distFront = 0;
int distRight = 0;
int distLeft  = 0;

int wall = 0;

void setup() {



  motorR.write(90);    //Right Forward  = 0
  motorL.write(90);  //Left Forward = 180


void loop() {

  distFront = * 10;
  distRight = * 10;
  distLeft  = * 10;

  //  Serial.println(distFront);
  //  Serial.println(distRight);
  //  Serial.println(distLeft);

  if (wall < 12 && distFront > 150 && distRight > 40 && distLeft > 40) {

    motorR.write(52); //move forward if no obstacles


  if (wall < 12 && distFront <= 150) {

    motorR.write(90); //stop if wall in front

    motorR.write(0); //turn left 90 degrees

    motorL.write(180); //go forwards again

    distFront = 1000;



  if (wall < 12 && distFront > 150 && distRight <= 40) {

    motorR.write(50); //turn left slightly if wall detected on right

    motorR.write(52); //forwards again


  if (wall < 12 && distFront > 150 && distLeft <= 40) {

    motorR.write(90); //turn right slightly if wall detected on left

    motorR.write(52); //forwards again


  if (wall = 12 && distFront <= 150) {

    motorR.write(90); //stop when race is finished

    wall = 13;


The robot functions perfectly besides being able to count walls. I thought that putting "wall++" in the "if (wall < 12 && distFront <= 150)" statement would increment the wall variable every time those conditions were met, but it seems that it stays at zero forever. Any idea on how to fix this/better approach this? I considered using a for or while loop but couldn't quite get those to function either. My programming skills aren't excellent, so any help is greatly appreciated. Thank you!

This line should probably use an equality test operator == instead of the assignment operator =.

With the = operator, it assigns wall = ( 12 && distFront <= 150); which, ... is always false because distFront can never be <=150 by the time it gets to this point in the loop, so wall is set to false which is zero.

Here's a hacked up and instrumented simulation: sketch.ino - Wokwi Arduino and ESP32 Simulator

The sim shows that wall++ is incrementing, but it gets reset to 0 by the end of the loop.


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= for assignment, == for compare.

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Why is it always the simplest thing... thanks for pointing that out!

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I doubt that,

I think it assigns a plain 12, evaluates to true and goes to the && operator and operand.

= is way down the list C Operator Precedence -

Adding the parentheses for <= gives:

wall = ( 12 && (distFront <= 150))

If distance happened to be < 150 at the beginning of the loop, the first conditional sets it to 1000. So here, distFront <=150) evaluates to false, then (12 && false) evaluates to false, and then 0 is assigned to wall.

I stand corrected.

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