I recently purchased the elm327 from an ebay site for $34 w/shipping (but-it-now cost). As far as double buffering??? - don't
see any with real-time updates. Interfacing to XP OS is simple and used scantool.net free version for code reading and real-time diagnostics. Read earlier that the ProScan 5.1 software is good, but interested if anyone else some ideas on the best software under $100???
Dave