# DFU Component

The DFU component is activated automatically at device startup if no valid application sub-image is found on the device. The application can also start the DFU component by calling the function Sys_Fota_StartDfu().

IMPORTANT: Sometimes smartphones do not handle a service changed indication correctly. Therefore, in the DFU initialization, the first two bits of the device’s Bluetooth address are set to 0 to force the smartphone to perform a service discovery.