The Lifestyle 20 and 50 require an IR converter box. It was an Audio Authority C-1024 sold as a Bose C-1024 IR converter. They used to be available on www.BluDo.com
but I no longer see them on their site. There are discrete IR codes for most everything. This was back in the bad old days of their marriage with Philips so there are bose published CCF files out there with all of the commands. I can send them to you if you need them.
The newer Lifestyle systems have an IR receiver built in and there are well documented codes for the 18, 28, 35, 38 and 48. You can find them in the RTI library. I also possess an excel generator file that will create codes for all Boselink rooms A-O.
As far as I know, the serial data port on the newer models are used to communicate with their add on video switcher. I could be wrong but I have been working with Bose product integration for quite some time and I have never run accross any published 232 protocol