Supply is 3.3V. I have another part where it plugs in and I can power it up and it reads CD.
UART pin seems to be response from the CD module to Main Board, because if I remove CD module there is nothing going on on that pin. I tried to remove CD module and sniff Main Board while clicking eject button but no signal found. Maybe it need to handshake and only then the command is sent... so more complex...
I have sniffed UART, STBY, RX, TX, BOOT pins while CD module was connected, but it seems that only UART is sending responses other pins are at constant state. Still I was not able to decode band rate of UART and dont know what kind of data was there.