found a great resource on spi, i2c , uart

the pro's and cons....

http://justanotherlanguage.org/book/export/html/164

You will also like this one SPI page - http://www.gammon.com.au/forum/?id=10892 -

it has other topics too - http://www.gammon.com.au/forum/bbshowpost.php?bbtopic_id=123 -

FYI, Nick Gammon is a frequent visitor here ;)