+ \begin{itemize}
+ \item GPIO In/Out/Direction is just another FN (effectively)
+ \item 3 wires: IN, OUT, OUTEN (=INEN\#)
+ \item FN however may be output-only (UART\_TX), input-only (UART\_RX)
+ or bi-directional (I2C\_SDA) and Bus-controlled.
+ \item GPIO is definitely bi-directional and under Register control
+ \end{itemize}