I should read more careful
Yellow is TX and needs to be connected to RX on the board, so there was nothing swapped except in my head. In any case, if someone wants to build this cable himself: here's what you need:
- A Samtec MEC1-108-02-*-D-* connector
- An FTDI TTL-232R-Rpi USB to serial/TTL cable
The Samtec connector is quite hard to come by. No local shop I queried could supply it and the handful of online vendors I found would not sell to a non-business. I got it from Farnell, which was not an all positive experience but they got me the part and that's what matters. As for the stars, there are multiple versions of this connector, using different contact material, surface or angle mount and some other options. It doesn't really matter which one you get, although you'll probably want to stay away from the 'NP' versions because these do not have the polarization bar (meaning you can plug it on reversed). The one I ordered was MEC1-108-02-L-D-RA1-SL and it cost me just under 4 euro.
The TTL-232R-Rpi is a stripped down version of the cable mentioned in the wiki
. It only has three wires but these are exactly the three wires you need. The bonus is that it costs about 10 euro less which is a good save for something you didn't need in the first place. The wires on the cable are also not open ended but have 0.1" pitch single connectors that will fit regular pin headers on a circuit board.
Additionally I used a piece of an old scsi-1 cable I had lying around in my "maybe it will be of use some day box" and a 4-pin break away header from which I pulled the third pin (so I know which pin is ground). This way I can simply detach the cable from the card edge connector and still use it on Pi as well.