I2C Scanner

The fast and easy way to find out the i2c devices connected to arduino. It also helps to find out whether the wiring is correct or not, usually people tend to interchange the SCL and SDA wire and waste a lot of time.

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#include <Wire.h> void setup() { Wire.begin(); Serial.begin(9600); Serial.println("\nI2C Scanner"); } void loop() { byte error, address; int nDevices; Serial.println("Scanning..."); nDevices = 0; for(address = 1; address < 127; address++ ) { // The i2c_scanner uses the return value of // the Write.endTransmisstion to see if // a device did acknowledge to the address. Wire.beginTransmission(address); error = Wire.endTransmission(); if (error == 0) { Serial.print("I2C device found at address 0x"); if (address<16) Serial.print("0"); Serial.print(address,HEX); Serial.println(" !"); nDevices++; } else if (error==4) { Serial.print("Unknow error at address 0x"); if (address<16) Serial.print("0"); Serial.println(address,HEX); } } if (nDevices == 0) Serial.println("No I2C devices found\n"); else Serial.println("done\n"); delay(5000); // wait 5 seconds for next scan }

Example:

Here you can see that four devices are attached to the board and their addresses in hex format.

Note: The addresses are 7-bit as you can see that the code searches only for addresses between 0 to 127.

Source : Arduino