I have a board similar to the iMX6Q Sabre SDB. I have the debug serial port connected to UART3 (pins EIM_D24/25). I am running the "Platform SDK (1.1) for MX6DQ TO1.2 Smart Device (SD) rev. C" I use the IOMux tool to configure UART3 on EIM_D24/25 pins. And in the source code to use UART3 as the debug uart. When I power up the board the Test Menu is displayed but my typed response is ignored. It appears as if the RX pin is not configured properly.