IR Obstacle Sensor on OLED: Obstacle Detection

What it is: An IR obstacle-avoidance sensor has an infrared LED and a receiver side by side. When something reflects the IR back, it flags an obstacle. It's the cheap "bumper" sensor on line-follower and obstacle-avoiding robots. How it works: It's a digital sensor — its OUT pin goes LOW when an obstacle is detected within range (a few cm to ~30 cm, set by the onboard trimmer). No analog reading needed. Wiring: IR OUT -> GPIO10 (digital) IR VCC -> 3V3 IR GND -> GND OLED VCC=3V3, GND=GND, SDA=GPIO4, SCL=GPIO5 Libraries: only "Adafruit SSD1306" and "Adafruit GFX Library". On screen / Serial: "CLEAR" or "OBSTACLE". Wave your hand in front of it and adjust the trimmer to set the trigger distance. Gotchas: OUT is active-LOW on almost all of these modules (LOW = obstacle), which is why the code inverts it. Range and reliability drop on dark or matte surfaces that absorb IR. Bright sunlight can cause false triggers.

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

Adafruit_SSD1306 display(128, 64, &Wire, -1);

#define IR 10                 // OUT on GPIO10 (digital, active-LOW)

void setup() {
  Serial.begin(115200);
  Wire.begin(4, 5);
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  pinMode(IR, INPUT);
}

void loop() {
  bool obstacle = digitalRead(IR) == LOW;      // LOW = obstacle detected

  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("IR Obstacle");
  display.setTextSize(2);
  display.setCursor(0, 26);
  display.println(obstacle ? "OBSTACLE" : "CLEAR");
  display.display();

  Serial.println(obstacle ? "OBSTACLE" : "clear");
  delay(120);
}