Firmware update status interface.
UpdateStatus getStatus()
Returns the device's firmware update status.
int elapsed
Seconds since start of update, 0 if not available.
string error_message
Error message; empty if there was no error.
string state
Current state of firmware update: NONE, INIT, PREP, SIMULATE, UPDATE, SUCCESS or FAIL.
int estimated
Estimated total time for update, 0 if not available.