I have exactly the same problem jaymonkey reported.
I changed the fex file to use uart on PH0 and PH1 which are correct according to the provided schematic. I'm using Multi4 function as per A20 user manual.
Changed script.bin and after rebooting I have uart3 on ttyS2.
Testing with screen /dev/ttyS2 19200 and a scope on pin 8 of CON3 (UART3.TX according to the schematic) but nothing is coming out.
Any update on this?
Did justine from sinovoip answered the question?
Regards
Snafutzz