GoForSmoke:
How does this compare to SPI?
SPI requires two lines (but usually uses three or four) instead of the one (but usually uses two) required for serial connections. Clocking is always performed by the master; neither the master nor the slave needs a calibrated clock. Serial requires both sides to have moderately calibrated clocks. The maximum bitrate of SPI is F_CPU / 2 (8 Mb/s). For asynchronous serial communications the maximum bitrate is F_CPU / 8 (2 Mb/s).
One reason is that every mobo I have owned for over 10 years now has SPI.
I wonder if that could be used for programming.