Sometimes it is worth making sure hardware flow control is OFF in minicom, and perhaps carrier detect too. Are you sure 9600 is correct? Most devices I encounter these days are 115200 it seems. https://lists.debian.org/debian-boot/2015/03/msg00314.html seems to mention 115200 on a Banana Pro.
both hardware flow control and carrier detect are set to off.I'm not sure 9600 is correct, the Arch wiki suggested it. But I've seen, the lemaker wiki http://wiki.lemaker.org/BananaPro/Pi:How_to_login_to_the_system#Using_the_TTL_serial_port recommends 115200, but still it doesn't boot.
in my previous tests e.g. with bananian, my bananapro worked fine - while booting that, a green light flashed up - which does not with debian jessie. ==> Although i didn't found the exact meaning of those light combinations, I'd assume that the OS didn't burn successfully.
Anyways, I've changed also my power adapter to a 1200 mA one, but that doesn't change anything.