
Source: http://2013.hackitoergosum.org/presentations/Day2-04.HackRF%20A%20Low%20Cost%20Software%20Defined%20Radio%20Platform%20by%20Benjamin%20Vernoux.pdf
The primary source of documentation is the wiki on github:
https://github.com/mossmann/hackrf/wiki
This directory contains supplemental documentation.
(photo jawbreaker-fd0-145436.jpeg by fd0 from https://github.com/fd0/jawbreaker-pictures)