File content as of revision 1:2363995f603f:

/* Scan I2C bus on specified pins and prints out
* the address of all pins where a active responder
* is found. 
*
* By Joe Elsworth CTO of A2WH
* Free use for al but no warranty, no promises.
* Don't forget 3K pullup sda,scl */

#include "mbed.h"


Serial pc(USBTX, USBRX);

 #define D_SDA                  PB_7 
 #define D_SCL                  PB_6 
   // sda=PB7, scl=PB_6 Pins specific to Nucleo-F303K8
  // must change pins to match your board.

I2C i2c(D_SDA, D_SCL);  
  
DigitalOut myled(LED1);
 
void scanI2C() {
  int address;
  int ack;  
  for(address=1;address<127;address++) {    
    ack = i2c.write(address, "11", 1);
    if (ack == 0) {
       pc.printf("\tFound at %3d -- %3x\r\n", address,address);
    }    
    wait(0.05);
  } 
}
 
int main() {
  pc.baud(9600);
  pc.printf("I2C scanner \r\n");
  scanI2C();
  pc.printf("Finished Scan\r\n");
  
  ack = i2c.write(71, "11", 1);
   
  while(1) { 
      wait(5.0);          
      myled = !myled;
  }
}