TCRT5000 IR Line Sensor with a Raspberry Pi Pico

// TCRT5000 IR Line Sensor on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/tcrt5000-module/raspberry-pi-pico
const int AO_PIN = 28;   // TCRT5000 A0: low over white, high over black
const int DO_PIN = 0;    // TCRT5000 D0: LOW over white, HIGH over black

// halfway between white (about 50) and black (about 930), with a margin either side
const int TO_BLACK = 600;  // above this: black
const int TO_WHITE = 400;  // below this: white
bool onLine = false;

void setup() {
  Serial.begin(9600);
  pinMode(DO_PIN, INPUT);  // the module has its own pull-up
  Serial.println("TCRT5000 ready");
}

void loop() {
  int level = analogRead(AO_PIN);
  if (!onLine && level > TO_BLACK) onLine = true;
  else if (onLine && level < TO_WHITE) onLine = false;

  Serial.print("A0 ");
  Serial.print(level);
  Serial.print("  D0 ");
  Serial.print(digitalRead(DO_PIN) == HIGH ? "HIGH" : "LOW");
  Serial.println(onLine ? "  line" : "  white");
  delay(100);
}