Why Your I2C Scanner Finds Nothing (And How to Fix It)

Why Your I2C Scanner Finds Nothing (And How to Fix It) You connect your I2C sensor. You upload the I2C scanner sketch. You open the serial monitor. It says "No I2C devices found." You check the wiring. You check the address in the datasheet. You try a different sensor. You try a different Arduino. Nothing works. I2C bus on breadboard — the pull-up resistors (4.7kΩ or 10kΩ) are essential. Without them, SDA and SCL stay at 0V and nothing communicates. You have a hardware problem. I2C is a bus, and