OpenWrt on Mikrotik RBM33G

Hi, I got a RBM33G but can't seem to find a way to actually install OpenWrt.

The wiki entry tells me to connect to serial, however neither 9600 nor 115200 works as a baud rate.

Setting up TFTP kinda works, as I see it downloading the kernel image (checked via tcpdump), however afterwards nothing ever happens. I guess as I don't set anything via RouterBOOT, which I'm unable to due to the missing serial console.

So, what could be the problem? Any hints?

got a voltmeter handy? check your rs-232 levels maybe?

"A special null-modem cable should be used for connecting to the serial console"
"some RouterBOARD models have reduced serial port functionality"

You can reconfigure RouterBOOT to enter the RouterBOOT menu only when a DEL character is received - use this to reduce the chance to get a router that's stuck when rebooting!

Or if newer versions are used "Silent boot" feature can be used to suppress any output on the serial interface, including removal of booting sounds.

( edit: wonder if those jumpers have anything to do with it? )