-            if scl == portScl and sda == portSda:
-                self._i2c = _I2C(portId, mode=_I2C.MASTER, baudrate=frequency)
-                break
+            try:
+                if scl == portScl and sda == portSda:
+                    self._i2c = _I2C(portId, mode=_I2C.MASTER, baudrate=frequency)
+                    busnum = portId
+                    break
+            except RuntimeError:
+                pass