If I may make a suggestion; I noticed when you were trying to use PORTD for UART, you initialized your TX Pin low (LATD = 0). I initialize my UART TX Pin high, as that is the idle state. Secondly, your WPUD didn't take advantage of the ability to bias your RX Pin high as well. You may get a false Start of Signal reading when your companion device initializes. Using a Weak Pull-Up on RX reduces that chance.