Retrieve the current manual ISO value
camera_error_t camera_get_manual_iso(camera_handle_t handle, unsigned *isovalue)
Use this function to retrieve the current manual ISO value. See also camera_set_manual_iso().
The viewfinder must be running before calling this function.
CAMERA_EOK when the function successfully completes, otherwise another camera_error_t value that provides the reason that the call failed.