The RSS buttons are much harder to find in the new look Flickr.
The API has not changed. I repeat it here,
http://api.flickr.com/services/feeds/photos_public.gne?id=${your_id}@N00&lang=en-us&format=rss_200
There is a thread in flickr’s forums,
http://www.flickr.com/groups/hackinguploadr/discuss/72157607379256227/
which documents the api.
14th June 2013