Dingoo A330 » Probing for RX Data

Looking for the RX data line, first I had to identify the TX data line (circled in green) then I tested the two nearest lines (cirled in red). The JZ-4740 pinout shows the TXD at ball P12 and the RXD at M12, but I have a feeling that they didn’t bother to connect RXD so it’s inaccessable.