Cannot read Controller Information on RobotBasic v2.8

[HuyK offline]

Hi all,

I cannot get roboBasic v2.8 communicates with my Robonova-II robots.

Here is the story:
Recently, I bought 2 robonova-ii robots (Metal Fighter robot) which are used ones with no programming cable.
So I built a custom cable using FT232RL USB to TTL Serial Adapter Module.
My cable connections are described in the attached picture.
When I open RoboBasic v2.8 and hit "Read Controller Information" button, I always got error -4 after the timeout.
Then I use a Serial Sniffer program to check communication lines between FT232 converter and the robot. I see RoboBasic sends 0xF0 but gets no response from the robot.
Then I follow connections on the board from the Host Communication Connector to AT Mega128 and see that there is a IC named U3 in between. So I solder a wire to RXD1 pin (pin 27) of ATMega128 to connect it to RX pin of FT232 converter in order to confirm what data ATMega128 receives and see it is always 0x00

I tried with both 2 robots and got the same result. So I suspect my cable has problem to interface with IC U3

Robot conditions when testing:
- Battery fully charged
- Can stand-up after switching on
- Controller board is MR-C3024FX v2.8

Why ATmega128 always receives 0x00 at RXD1 pin when FT232 Converter sends 0xF0 to IC U3?
Can I use FT232 Converter like the cable I made? Should I miss anything to make the cable works with IC U3?

Thanks