I2CScanner.ino

Scans the I2C bus on the SDA/SCL header pins every 5 s and prints every address from 0x08 to 0x77 that answers.

Each address is probed with PhyduinoWire::beginTransmission() and PhyduinoWire::endTransmission() with no data; 0 means a device answered.

Wiring

One or more I2C devices on SDA, SCL, 3.3 V and GND.

Output

Serial Monitor at 115200 baud, for example:

Device at 0x3C
1 device(s) found.

Note

The board has no I2C pull-up resistors, only the RP2040's weak internal ones. Add 4.7 kOhm resistors to 3.3 V for long wires or 400 kHz.

// Scans the I2C bus (SDA/SCL header pins) and prints every address that answers.
#include <Wire.h>
 
void setup() {
    Serial.begin(115200);
    while (!Serial) {}
    Wire.begin();
}
 
void loop() {
    int found = 0;
    for (uint8_t address = 0x08; address < 0x78; address++) {
        Wire.beginTransmission(address);
        if (Wire.endTransmission() == 0) {
            Serial.print("Device at 0x");
            Serial.println(address, HEX);
            found++;
        }
    }
    Serial.print(found);
    Serial.println(" device(s) found.");
    delay(5000);
}