Marlin upload

Hello,

I am trying to upload Marlin firmware to my arduino mega 2560, from Windows 7 64bit.

The compilation and upload seem to work, (confirmation of done compiling/uploading)

When I send a M115 in the serial monitor, I see the RX led on the board flash,
but I don’t get any response of it, even though com3 port and baud rate 115200 are correctly set.

Ultimately when I try to connect from Repetier to the printer, it puts all commands on waiting.

what am I doing wrong?

oh, forgot to mention, if i try to connect with repetier host, it says "no start signal detected". It also won't connet properly if I deactivate reset on connect...