I seem to have an odd, recurring interest in the internal serial port on the MP2x00. A few years back I tried to make an internal bluetooth module. It worked, but I never got the RF design correct so it didn't work well.
Now, I'd like to try for an internal WiFi module. I'm more hopeful that I can get the antenna correct by using more off the shelf components and, worst case, an external antenna.
The internal port was originally designed for an internal modem that was never produced. Luckily, some of the design documents were leaked and are now available. The documents give you part of the picture, but there are omissions and errors that make the process a bit more of an exercise in reverse engineering.
I wanted a breakout board that would help prototype and test the behavior of some of the GPIO pins and such. I came up with this:
The connector is a FTE-116-01-G-DV-ES. It is easier to find without the -ES option, FTE-116-01-G-DV-P for example is available from Newark electronics. The ES is just an end shroud, which while a nice thing, is not strictly necessary. I think the pins are a little longer than the original JAE connector, so it sits a little high. The case seems to close so I'm hopeful that it'll work for an internal card as well.
I had 20 of these boards made for $15. You'll have to solder the connector on there yourself, but if you're playing around with this sort of thing, you probably know how to handle surface mount pins of this size.