Fr:Circuit électronique du BoB
EXT Port Connection:
Warning: according to this thread, the JTAG pinout is wrong.
The JTAG pinout is correct. Several people have made JTAG adapters successfully using that pinout. I (Robster) have a JTAG adapter that works on an early First Edition GP2X and also a Mk2 GP2X. It's possible that GPH have altered the pinout for other versions, but pretty unlikely.
Note: on Mk2 GP2X, the nRESET line function has changed, and it no longer resets the GP2X.
VUSB Boost from 3.3v to 5v:
S-Video to Composite:
RS232 Level Shifting: