#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin(PB7, PB6); // Blue Pill I2C1
  Serial.println("I2C scan start");
}

void loop() {
  byte error, address;
  int found = 0;

  for (address = 1; address < 127; address++) {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0) {
      Serial.print("Found device at 0x");
      if (address < 16) Serial.print("0");
      Serial.println(address, HEX);
      found++;
    }
  }
  if (!found) Serial.println("No I2C devices found");
  delay(3000);
}