[coreboot] DIY debug Dongle

Hi
I've seen an EHCI debug dongle in the old wiki. I'm trying to build one for
2 purposes: debug a homebrew os/Shell and make it a new UEFI bootloader.
However I don't know where to find further documentation or comments about
this. I also dont' know what is the current or most up to date schematic to
build the "sandwich" and what tracks cut and what not. I have bought those
blue cypress FX2LP boards and I don't know how to check revisions. Also,
I'dont know exactly what software can be used to control it. It would be
desirable if one can send stop or install some breakpoints with Visual
studio's debugger or WinDBG or GDB or something like that.
thanks in advance for your advice.